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					                                                                                                                            Biology II 1
                                                                                                  Chapter 11 Introduction to Genetics

Tabla de contenido
Summary ................................................................................................................................................. 2
Vocabulary Review ................................................................................................................................. 3
Dominance .............................................................................................................................................. 4
Section Assessment 11-1 ........................................................................................................................ 4
Workbook Section 11–1 The Work of Gregor Mendel (pages 263–266) ............................................... 5
Section Review 11-1 ............................................................................................................................... 7
Homozygous or Heterozygous? .............................................................................................................. 8
11-2 Probability and Punnett Square ...................................................................................................... 8
Enrichment -- Animal Pedigrees—A Canine Family Tree ..................................................................... 9
Workbook Section 11–2 Probability and Punnett Squares (pages 267–269)........................................ 10
11-2 Reviewing Key Concepts ............................................................................................................. 11
F2 Generation Punnett Square .............................................................................................................. 12
11-3 Exploring Mendelian Genetics ..................................................................................................... 12
Workbook Section 11–3 Exploring Mendelian Genetics (pages 270–274) .......................................... 13
Section Review 11-3 ............................................................................................................................. 15
Chapter 11 Assessment ......................................................................................................................... 16
Vocabulary Review ................................................................................................................................ 18
                                                                                         Biology II 2
                                                               Chapter 11 Introduction to Genetics

Summary
11–1 The Work of Gregor Mendel
The scientific study of heredity is called genetics. Gregor Mendel used purebred pea plants in
a series of experiments to understand inheritance.
        Pea flowers have both male and female parts. Normally, pollen from the male part of
the pea flower fertilizes the female egg cells of the same flower. This is called selfpollination.
Seeds that come from selfpollination inherit all their characteristics from just one parent.
        To carry out his experiments, Mendel had to prevent self-pollination. He did this by
cutting away the male parts and then dusting pollen from another plant on the flower. This
process is called cross-pollination. The seeds that come from cross-pollination are the
offspring of two different parents. Mendel decided to study just a few traits, or
characteristics, of the pea plants. He studied seven traits: seed shape, seed color, seed coat
color, pod shape, pod color, flower position, and plant height.
        First, Mendel crossed two plants with different characters, or forms, for the same trait.
For example, one plant was tall and the other was short. Mendel used the seeds produced by
this cross to grow plants. These plants were hybrids. Hybrids are the offspring of crosses
between parents with different traits.
        To Mendel’s surprise, the hybrid plants looked like only one of the parents. He
concluded that each trait was controlled by one gene that occurred in two different forms. The
different forms of a gene are called alleles. Mendel formed the theory of dominance. He
concluded that some alleles are dominant, while others are recessive. Whenever a living thing
inherits a dominant allele, that trait is visible. The effects of a recessive allele are not seen if
the dominant allele is present.
        Mendel wanted to know what happened to the recessive allele. He allowed his hybrid
plants to self-pollinate. Some of the plants that were produced showed the recessive trait. The
alleles responsible for the recessive characters had not disappeared. Before, the dominant
allele had masked the recessive allele, so it was not visible. Mendel concluded that the alleles
for the same trait can be separated. He called this segregation. Alleles segregate when sex
cells, or gametes, are formed. Each gamete carries only one copy of each gene.
11–2 Probability and Punnett Squares
Mendel used the principles of probability to explain his results. Probability is the likelihood
that a particular event will occur. Probability can be used to predict the outcome of genetic
crosses because alleles segregate randomly. The gene combinations that might result from a
genetic cross can be determined by drawing a Punnett square.
        One important rule of probability is that probabilities predict the average outcome of a
large number of events. They cannot predict what will happen in a single event. The more
organisms examined, the closer the numbers will get to the expected values. This is why
Mendel worked with thousands of pea plants.
11–3 Exploring Mendelian Genetics
Mendel wondered whether genes that determine one trait have anything to do with genes that
determine another trait. He wanted to know, for example, whether the gene that determines
seed shape affects the gene for seed color. To answer this question, he did an experiment. He
crossed plants and recorded two traits—seed shape and seed color.
        Mendel found that the gene controlling seed shape did not affect the gene controlling
seed color. Mendel concluded that genes can segregate independently, or undergo
independent assortment, during gamete formation.
        Not all genes show simple patterns of dominant and recessive alleles. In incomplete
dominance, one allele is not completely dominant over another. In codominance, both alleles
contribute to the phenotype. Many genes have more than two alleles and are said to have
multiple alleles. Polygenic traits are traits controlled by two or more genes. The
                                                                                        Biology II 3
                                                              Chapter 11 Introduction to Genetics

characteristics of any organism are not caused only by its genes. Instead, characteristics are
determined by the interaction between the genes and the environment
11–5 Linkage and Gene Maps
Some genes are almost always inherited together. These genes belong to the same linkage
group. A chromosome is a group of linked genes. It is actually the chromosomes that assort
independently during gamete formation, not single genes.
        The location of genes can be mapped to a chromosome. The rate of crossover events
is used to find the distance between genes on a chromosome. The farther apart two genes are,
the more likely they will be separated by a crossover event.
Vocabulary Review
Labeling Diagrams Use the words listed below to label the Punnett square. Some words may
be used twice.
                heterozygous parent homozygous offspring
                dominant allele      heterozygous offspring
                recessive allele




Matching In the space provided, write the letter of the definition that best matches each
term.
_____ 7. phenotype                                 a. likelihood that something will happen
_____ 8. gamete                                    b. shows the relative locations of genes on
_____ 9. genetics                                  a chromosome
_____ 10. probability                              c. physical characteristics of an organism
_____ 11. haploid                                  d. containing one set of chromosomes
_____ 12. gene map                                 e. sex cell
_____ 13. gene                                     f. chemical factor that determines traits
_____ 14. multiple alleles                         g. specific characteristic
_____ 15. Trait                                    h. scientific study of heredity
                                                   i. gene with more than two alleles


Completion Fill in the blanks with terms from Chapter 11.
16. The process in which two genes segregate independently is called _____________.
17. Plants that, if left to self-pollinate, produce offspring identical to themselves are called
______________.
18. The offspring of crosses between parents with different traits are called
_______________.
19. The process during sexual reproduction in which male and female sex cells join is called
__________________.
20. The process of reduction division in which the number of chromosomes per cell is cut in
half is called ________________.
                                                                                      Biology II 4
                                                            Chapter 11 Introduction to Genetics

Dominance
Mendel’s principle of dominance states that some alleles are dominant and others are
recessive. An organism with a dominant allele will show the dominant form of the trait. An
organism will only express the recessive form of a trait when a dominant allele is not present.
In the space provided, fill in the genotype of the offspring. The first one has been done for
you.




Use the table to answer the questions. Circle the correct answer.
1. What is the dominant shape of a pea pod?
                                 Constricted            smooth
2. What is the recessive color of a pea plant’s seed coat?
                                   white                  gray


Section Assessment 11-1
1-     What are dominant and recessive alleles?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
2-     What is segregation? What happens to alleles during segregation?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
3-     What did Mendel conclude determines biological inheritance?
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                                                               Chapter 11 Introduction to Genetics

___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
4-    Determine how Mendel crosspollinated pea plants.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
5-    Why did only about one fourth of Mendel’s F2 plants exhibit the recessive trait?
___________________________________________________________________________
___________________________________________________________________________
6-    Why were true- breeding pea plants important for Mendel’s experiments?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________


Workbook Section 11–1 The Work of Gregor Mendel (pages 263–266)
This section describes how Gregor Mendel studied the inheritance of traits in garden peas and what
his conclusions were.
Introduction (page 263)
1. The scientific study of heredity is called __________________________.
Gregor Mendel’s Peas (pages 263–264)
2. Circle the letter of each sentence that is true about Gregor Mendel’s peas.
        a. The male parts of pea flowers produce eggs.
        b. When pollen fertilizes an egg cell, a seed for a new plant is formed.
        c. Pea plants normally reproduce by self-pollination.
        d. Seeds that are produced by self-pollination inherit their characteristics from two
        different plants.
3. What does it mean when pea plants are described as being true-breeding?
__________________________________________________________________________________
__________________________________________________________________________________
_________________________________________________________________________________

4. To perform his experiments, how did Mendel prevent pea flowers from self-pollinating and
control their cross-pollination?
__________________________________________________________________________________
__________________________________________________________________________________
_________________________________________________________________________________

Genes and Dominance (pages 264–265)
Match the term with its definition.
Definitions                                           ____ 8. The different forms of a gene
____ 5. Specific characteristics that vary
from one individual to another                        Terms
____ 6. The offspring of crosses between              a. genes
parents with different traits                         b. hybrids
____ 7. Chemical factors that determine               c. traits
traits                                                d. alleles
                                                                                      Biology II 6
                                                            Chapter 11 Introduction to Genetics



9. State the principle of dominance. ______________________________________________
___________________________________________________________________________
___________________________________________________________________________
10. Is the following sentence true or false? An organism with a recessive allele for a
particular form of a trait will always exhibit that form _____________________________


11. Circle the letters of the traits controlled by dominant alleles in Mendel’s pea plants.
                a. tall          b. short       c. yellow      d. green
Segregation (pages 265–266)
12. How did Mendel find out whether the recessive alleles were still present in the F1
plants?_____________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
13. About one fourth of the F2 plants from Mendel’s F1 crosses showed the trait controlled
by _________________________ the allele.
14. Circle the letter of each sentence that is true about Mendel’s explanation of the results
from his F1 cross.
       a. Mendel assumed that a dominant allele had masked the corresponding recessive
       allele in the F1 generation.
       b. The trait controlled by the recessive allele never showed up in any F2 plants.
       c. The allele for shortness was always inherited with the allele for tallness.
       d. At some point, the allele for shortness was segregated, or separated, from the allele
       for tallness.
15. What are gametes? ___________________________________________________
16. Complete the following diagram to show how alleles segregate during the formation of
gametes.
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                                                            Chapter 11 Introduction to Genetics

17. In the diagram above, the dominant allele is represented by ________________ and the
recessive allele is represented by ________________________.


Section Review 11-1

Reviewing Key Concepts
Short Answer On the lines provided, answer the following questions.
1. State Mendel’s principle of dominance.
___________________________________________________________________________
___________________________________________________________________________

2. Which two combinations of alleles could produce a trait controlled by a dominant allele?
___________________________________________________________________________
___________________________________________________________________________

3. What combination of alleles could produce a trait controlled by a recessive allele?
___________________________________________________________________________
___________________________________________________________________________

4. Explain segregation of alleles, using pea plant traits in your example.
___________________________________________________________________________
___________________________________________________________________________

Reviewing Key Skills
5. Applying Concepts Explain how Mendel’s experiments would have been different if he
had not worked with true-breeding plants.
___________________________________________________________________________
___________________________________________________________________________

6. Comparing and Contrasting Explain the difference between crosspollination and self-
pollination in plants.
___________________________________________________________________________
___________________________________________________________________________

7. Calculating One fourth of the plants resulting from a certain cross are expected to show a
trait controlled by a recessive allele. If 675 plants resulting from the cross display a trait
controlled by a dominant allele, how many plants will show the trait controlled by the
recessive allele?
___________________________________________________________________________
___________________________________________________________________________

8. Applying Concepts If one of the plants used in the F1 cross had TT alleles and was
combined with a plant with Tt alleles, would the trait controlled by the recessive allele have
been produced in the resulting F2 generation? Explain your answer.
___________________________________________________________________________
___________________________________________________________________________
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                                                           Chapter 11 Introduction to Genetics

Homozygous or Heterozygous?
Homozygous organisms have two identical alleles for a particular trait. Heterozygous
organisms have two different alleles for the same trait.
Color the homozygous recessive plant yellow. Color the homozygous dominant plant red.
Color the heterozygous plant orange. In the space provided, fill in the missing genotype.




Use the diagram to answer the questions.
1. Does the tall offspring plant look like the tall parent plant? Explain.
___________________________________________________________________________
___________________________________________________________________________

2. Why did you color the offspring plant a different color than the tall parent plant?
___________________________________________________________________________
___________________________________________________________________________

11-2 Probability and Punnett Square
1-     How are the principles of probability used to predict the outcomes of genetic crosses?
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
______________________________________________________
2-     How are Punnett squares used?
__________________________________________________________________________________
__________________________________________________________________________________
3-     What is probability?
__________________________________________________________________________________
__________________________________________________________________________________
4-     Define the terms genotype and phenotype.
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
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                                                           Chapter 11 Introduction to Genetics

5-      A F1 plant that is homozygous for shortness is crossed with a heterozygous F1 plant.
What is the probability that a seed from the cross will produce a tall plant? Use a Punnett
square to explain your answer and to compare the probable genetic variations in the F2
plants.
___________________________________________________________________________




Enrichment -- Animal Pedigrees—A Canine Family Tree
Where did the dog come from? If you look
at the hypothetical family tree shown here,
you can see that the canine group began
evolving about 30 million years ago from a
tiny treeclimbing animal, Miacis.
        The dog appears to be the first
animal domesticated by humans. DNA
evidence indicates that dogs were initially
domesticated from wolves about 100,000
years ago. Tribes used dogs for help with
hunting, for protection at night, and for
companionship.
        After dogs were domesticated, they
were selectively bred for particular
characteristics. Just as other domesticated
animals have been bred, dogs were bred so
that they had the characteristics most
desired by humans. In different parts of the
world, the choice of desirable
characteristics varied, resulting in the
diversity we see today.
        As dogs continued to live as human
companions, many new breeds were
developed for specific tasks, such as
hunting, guarding, working, and
companionship.
        The basic principles of dog
breeding are those that apply to any
animal. Breeding pairs are selected for the desirable genes they will pass on. Some
characteristics involve single-gene inheritance. However, many characteristics, such as coat
color, depend on more than one gene. A cross between two heterozygous parents can produce
a puppy with blue eyes even though both parents have brown eyes. In German Shepherds, the
alleles for white fur and dark eyes are recessive. Two black or two tan parent dogs can still
produce a white puppy.
Evaluation Answer the following questions on a separate sheet of paper.
1. When were dogs first domesticated?

2. If a homozygous German Shepherd with dark eyes is bred with a heterozygous German
Shepherd with light eyes, is it possible to have puppies with dark eyes? Explain your answer.
                                                                                        Biology II 10
                                                              Chapter 11 Introduction to Genetics

Workbook Section 11–2 Probability and Punnett Squares (pages 267–269)
This section explains how geneticists use the principles of probability.
Genetics and Probability (page 267)
1. The likelihood that a particular event will occur is called ___________________.
2. Circle the letter of the probability that a single coin flip will come up heads.
        a. 100 percent          b. 75 percent c. 50 percent             d. 25 percent
3. Is the following sentence true or false? The past outcomes of coin flips greatly affect the
outcomes of future coin flips. ____________________
4. Why can the principles of probability be used to predict the outcomes of genetic
crosses? ____________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

Punnett Squares (page 268)
5. How do geneticists use Punnett squares?________________________________________
___________________________________________________________________________
6. Complete the Punnett square to show the possible gene combinations for the F2 offspring




Match the terms with the definitions.
Definitions
____ 7. Organisms that have two identical           Terms
alleles for a particular trait (TT or tt)           a. genotype
____ 8. Organisms that have two different           b. homozygous
alleles for the same trait (Tt)                     c. phenotype
____ 9. Physical characteristic of an               d. heterozygous
organism (tall)
____ 10. Genetic makeup of an organism
(Tt)

11. Is the following sentence true or false? Homozygous organisms are true-breeding
for a particular trait. _________________
12. Is the following sentence true or false? Plants with the same phenotype always
have the same genotype. _________________
Probability and Segregation (page 269)
13. Circle the letter of each sentence that is true about probability and segregation.
        a. In an F1 cross between two hybrid tall pea plants (Tt), 1⁄2 of the F2 plants will have
        two alleles for tallness (TT).
                                                                                         Biology II 11
                                                               Chapter 11 Introduction to Genetics

        b. The F2 ratio of tall plants to short plants produced in a cross between two hybrid
        tall pea plants (Tt) is 3 tall plants for every 1 short plant.
        c. Mendel observed that about 3⁄4 of the F2 offspring showed the dominant trait.
        d. Segregation occurs according to Mendel’s model.
14. In Mendel’s model of segregation, what was the ratio of tall plants to short plants in
the F2 generation? _____________________________________
Probabilities Predict Averages (page 269)
15. Is the following sentence true or false? Probabilities predict the precise outcome of an
individual event. __________________________
16. How can you be sure of getting the expected 50 : 50 ratio from flipping a coin?
___________________________________________________________________________
17. The____________________ the number of offspring from a genetic cross, the closer the
resulting numbers will get to expected values.
18. Is the following sentence true or false? The ratios of an F1 generation are more likely to
match Mendelian predicted ratios if the F1 generation contains hundreds or thousands of
individuals. ___________________________

11-2 Reviewing Key Concepts
Short Answer On the lines provided, answer the following questions.
1. What is probability and how is it used in genetics?
__________________________________________________________________________________________
__________________________________________________________________________________________
2. How are Punnett squares used in genetics?
____________________________________________________________________________________________________
____________________________________________________________________________________________________
Reviewing Key Skills
3. Problem Solving If a heterozygous plant for seed color (Rr) is crossed with a homozygous
recessive plant (rr), what is the probability of each seed color being produced? Explain your
answer using a Punnett square.
___________________________________________________________________________
___________________________________________________________________________
4. Comparing and Contrasting How are homozygous and heterozygous genotypes for a
particular trait in plants different? Give an example of a genotype for each.
___________________________________________________________________________
___________________________________________________________________________
5. Applying Concepts How can two plants that have different genotypes have the same
phenotype?
___________________________________________________________________________
___________________________________________________________________________

Interpreting Graphics For questions 6 to 9, fill in the genotype and percentage expected on
the lines provided.
                                                                                         Biology II 12
                                                               Chapter 11 Introduction to Genetics


F2 Generation Punnett Square
In the space provided, fill in the missing genotypes as either Tt or tt. In this example, T _ tall
and t _ short.




Use the Punnett square to answer the questions.
1. Write the phenotypes of the three genotypes shown above.
TT _____________ tt ______________ Tt_______________
2. If two heterozygous plants create four offspring, how many do you predict would be tall?
How many do you predict would be short?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

11-3 Exploring Mendelian Genetics

1-    Explain what independent assortment means.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
2-    Describe two inheritance patterns besides simple dominance.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
3-    What is the difference between incomplete dominance and codominance?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
4-    Why are fruit flies an ideal organism for genetic research?
                                                                                      Biology II 13
                                                            Chapter 11 Introduction to Genetics

___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
5-      A geneticist studying coat color in animals crosses a male rabbit having the genotype
CC with a female having genotype Ccch. The geneticist then crosses a ccch male with Ccc
female. In which of the two crosses are the offspring more likely to show greater genetic
variation? Use punnett square to explain your answer.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

Workbook Section 11–3 Exploring Mendelian Genetics (pages 270–274)
This section describes Mendel’s principle of independent assortment. It also tells about traits
that are controlled by multiple alleles or multiple genes.
Independent Assortment (pages 270–271)
1. In a two-factor cross, Mendel followed ___________________ different genes as they
passed from one generation to the next.
2. Write the genotypes of the true-breeding plants that Mendel used in his two-factor
cross.
         Phenotype                                   Genotype
         a. round yellow peas                        __________________________
         b. wrinkled green peas                      __________________________

3. Circle the letter that best describes the F1 offspring of Mendel’s two-factor cross.
        a. Homozygous dominant with round yellow peas
        b. Homozygous recessive with wrinkled green peas
        c. Heterozygous dominant with round yellow peas
        d. Heterozygous recessive with wrinkled green peas
4. Is the following sentence true or false? The genotypes of the F1 offspring indicated to
Mendel that genes assort independently. ______________________
5. How did Mendel produce the F2 offspring? _____________________________________
___________________________________________________________________________
6. Circle the letter of the phenotypes that Mendel would expect to see if genes segregated
independently.
        a. round and yellow
        b. wrinkled and green
        c. round and green
        d. wrinkled and yellow
7. What did Mendel observe in the F2 offspring that showed him that the alleles for seed
shape segregate independently of those for seed color?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

8. What were the phenotypes of the F2 generation that Mendel observed?
                                                                                      Biology II 14
                                                            Chapter 11 Introduction to Genetics

___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

9. What was the ratio of Mendel’s F2 generation for the two-factor cross?
_________________________________________
10. Complete the Punnett square below to show the predicted results of Mendel’s two factor
cross.




11. State Mendel’s principle of independent assortment. _____________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
A Summary of Mendel’s Principles (page 272)
12. Circle the letter of each sentence that is true about Mendel’s principles.
        a. The inheritance of biological characteristics is determined by genes that are passed
        from parents to their offspring.
        b. Two or more forms of the gene for a single trait can never exist.
        c. The copies of genes are segregated from each other when gametes are formed.
        d. The alleles for different genes usually segregate independently of one another.
13. When two or more forms of the gene for a single trait exist, some forms of the gene may
be _______________ and others may be _________________.
Beyond Dominant and Recessive Alleles (pages 272–273)
14. Is the following sentence true or false? All genes show simple patterns of dominant
and recessive alleles _______________________

15. Complete the compare-and-contrast table of the different patterns of inheritance.
                                                                                      Biology II 15
                                                            Chapter 11 Introduction to Genetics




Applying Mendel’s Principles (page 274)
16. List three criteria Thomas Hunt Morgan was looking for in a model organism for
genetic studies.
        a. ______________________________________________________________
        b. ______________________________________________________________
        c. ______________________________________________________________
17. Is the following sentence true or false? Mendel’s principles apply not just to pea plants
but to other organisms as well. _______________________
Genetics and the Environment (page 274)
18. Characteristics are determined by interaction between genes and the ________________.

Section Review 11-3
Reviewing Key Concepts
Completion On the lines provided, complete the following sentences.
1. The principle of independent assortment states that genes for different traits can
_____________________ independently during the formation of gametes.
2. Some alleles are neither dominant nor recessive, and many traits are controlled by
____________________ or _________________.
Matching On the lines provided, write the letter of the type of inheritance next to its
description.
       a. incomplete dominance b. codominance c. multiple alleles d. polygenic traits
_______ 3. both alleles contribute to the phenotype of the organism
_______ 4. more than two possible alleles for a trait exist in a population
_______ 5. traits controlled by two or more genes
_______ 6. one allele is not completely dominant over the other allele
                                                                                     Biology II 16
                                                           Chapter 11 Introduction to Genetics


Reviewing Key Skills
7. Applying Concepts A geneticist crosses two plants with the
genotypes FfJj and FFJj.




8. Comparing and Contrasting What is the difference between a heterozygous phenotype
produced by incomplete dominance and a heterozygous phenotype produced by
codominance?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

9. Applying Concepts Do polygenic traits or single-gene traits have more variation in the
phenotypes they produce? Explain your answer.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________


10. Inferring Why did Morgan choose fruit flies for his genetic studies?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________


Chapter 11 Assessment
1-    Different forms of a gene are called
      a-     Hybrid                                       c-      Alleles
      b-     Dominant factors                             d-      Recessive factors
2-    If a homozygous tall pea plant and a homozygous chort pea plant are crossed,
   a- The recessive trait seems to                    c- No hybrid are produced
      disappear                                       d- All the offspring are short
   b- The offspring are of medium height
3-    A Punnett square is used to determine the
   a- Probable outcome of a cross                     c- Result of mitosis
   b- Actual outcome of a cross                       d- Result of meiosis
4-    Organisms that have two identical alleles for a particular trait are said to be
   a- Hybrid                                          c- Homozygous
   b- Heterozygous                                    d- dominant
5-    The physical characteristics of an organism are its
   a- Genetics                                        c- Phenotype
   b- Heredity                                        d- genotype
6-    A situation in which a gene has more than two alleles is known as
   a- Complete dominance                              c- Polygenic dominance
   b- Codominance                                     d- Multiple alleles
                                                                                      Biology II 17
                                                            Chapter 11 Introduction to Genetics

7-       List the four basic principles of genetics that Mendel discovered in his experiments.
Briefly describe each of these principles.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
8-       What is probability? How does probability relate to genetics?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
9-       In pea plants, the allele for yellow seeds is dominant to the allele for green seeds.
Predict the genotypic ratio of offspring produced by crossing two parents heterozygous for
this trait. Draw a punnet square to illustrate your prediction.
___________________________________________________________________________




10-   How do multiple alleles and polygenic traits differ?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

11-   Why can multiple alleles provide many different phenotypes for a trait?
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

12-   Are an organism’s characteristics determined only by its gene? Explain.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________

13-    In rabbits, B is an allele for black coat and b is an allele for brown coat. Write the
genotypes for a rabbit that is homozygous for black coat and another rabbit that is
heterozygous for black coat.
___________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
                                                                              Biology II 18
                                                    Chapter 11 Introduction to Genetics

Vocabulary Review
Hidden Word Use the clues to write the correct vocabulary term from the words
below in the blanks.
              diploid   genetics       hybrid       probability trait
                gene homozygous          meiosis      Punnett square




Use the circled letter in each term to find the hidden vocabulary word.
10.Hidden Word: ___ ___ ___ ___ ___ ___ ___ ___ ___
Write a definition for the hidden word.
Definition: ___________________________________________________________
___________________________________________________________________________

				
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