Writing Alleles Answer Sheet 01

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Name _____________________________Date _______________ Period ________
Genetics Practice Problems #2 - Writing Alleles
Directions: Using the data in Table 1, write the genotype that corresponds to the phenotype
descriptions

Table 1: Mendel's Traits and Symbols for Pea Plants
Traits Dominant Allele Symbol Recessive Allele Symbol
Seed Shape Round R Wrinkled r
Seed Color Yellow Y Green y
Seed Coat Color Colored C White c
Pod Shape Smooth S Constricted s
Pod Color Green G Yellow g
Stem Height Tall T Short t
Flower Position Axial A Terminal a

Phenotype Genotype Phenotype Genotype

1. Heterozygous for height 16. Constricted pod

2. Homozygous dominant for seed shape 17. Short height

3. Heterozygous colored seed coat 18. Green seed color

4. Homozygous green pod 19. Terminal flowers

5. Homozygous short 20. Pure wrinkled

6. Homozygous tall 21. Hybrid tall

7. Homozygous axial 22. Pure round

8. Homozygous terminal 23. Yellow seed pod

9. Heterozygous flower position 24. Hybrid smooth

10. Heterozygous seed color 25. Pure smooth pod

11. Homozygous smooth pod 26. Hybrid pod color

12. Homozygous constricted pod 27. White seed coat

13. Homozygous recessive for seed coat color 28. Wrinkled seed

14. Heterozygous for pod color 29. Pure colored seed coat

15. Homozygous round seed 30. Hybrid flower position
Name _____________________________Date _______________ Period ________
Genetics Practice Problems #5 - Monohybrid Problems Worksheet 2
Directions: Using the table and rules below, complete Table 2 solving for the following:
 symbolic representation of the parents (assume the first to be the male)
 male and female gametes
 phenotypic ratio
 genotypic ratio

Use a separate sheet of paper to set up and solve your problems. Work must be shown to
receive credit. Attach work for credit.

Rules for writing symbols
1. Dominant alleles are always capitalized usually by using the first letter of the trait as the symbol.
2. The recessive allele is always represented by the small case letter of the symbol for the dominant allele.

Problem Set 1

1. Heterozygous for seed color x Homozygous recessive for seed color

2. Heterozygous for flower position x Heterozygous for flower position

3. Homozygous dominant for seed shape x Heterozygous for seed shape

4. Homozygous dominant for stem height x Homozygous recessive for stem height

5. Homozygous recessive for seed coat color x Heterozygous for seed coat color

6. Heterozygous seed color x Homozygous dominant for seed color

7. Constricted pea pod x Constricted pea pod

8. Yellow pod x Homozygous dominant for pod color

9. Homozygous long x Homozygous long

10. Homozygous smooth x constricted pod shape.
Table 2 Answers to monohybrid problems
Parent Genotypes Male Gametes Female Gametes Phenotypic Ratio Genotypic Ratio
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Name _____________________________Date _______________ Period ________

Genetics Practice Problems #4 - Monohybrid Problems Worksheet 1

Directions: Using the table and rules below, complete Table 2 solving for the following:
 symbolic representation of the parents (assume the first to be the male)
 male and female gametes
 phenotypic ratio
 genotypic ratio

Use a separate sheet of paper to set up and solve your problems. Attach work showing
Punnett Squares to receive credit.

EXAMPLE: homozygous recessive for stem length X heterozygous for stem height

Genotypes Phenotype Traits
Parents (P1) tt x Tt T = tall stem
Gametes (G1) t,t,T,t t = short stem

T t Phenotypic Ratio = 2:2 Tall stem: Short stem or 1 tall stem:1 short stem

t Tt tt Genotypic Ratio = 1:1...
tl Tt tt Heterozygous for stem height : Homozygous recessive for stem height
.....

1. Heterozygous for seed color x Homozygous dominant for seed color

2. Heterozygous for flower position x Heterozygous for flower position

3. Homozygous recessive for seed shape x Heterozygous for seed shape

4. Homozygous dominant for stem height x Homozygous recessive for stem height

5. Homozygous recessive for seed coat color x Heterozygous for seed coat color

6. Heterozygous seed color x Homozygous recessive for seed color

7. Constricted pea pod x Constricted pea pod

8. Yellow pod x Homozygous dominant for pod color

9. Homozygous tall x Homozygous tall

10. Homozygous axial x Terminal flower position

Table 2 Answers to monohybrid problems
Parent Genotypes Male Gametes Female Gametes Phenotypic Ratio Genotypic Ratio
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Name _____________________________Date _______________ Period ________

Genetics Practice Problems #6 - Monohybrid Problems Worksheet

Directions: Show all work including Punnett squares.

1. Assume the allele B is dominant for black fur in rats. The recessive allele is for white fur.
If one of the parents of the F1 generation was homozygous dominant and the other was
homozygous recessive, describe the phenotypes (1a) and genotypes (1b) of the F 1
generation. How many of the offspring (F1) generation would be homogenous dominant
(1c), homozygous recessive (1d), and heterozygous (1e)?

1a.

1b.

1c.

1d.

1e.

2. If the offspring from the F1 generation in problem #1 were crossed with each other,
what would be the genotypic ratio of the F2 generation?

3. What are the chances of producing a homozygous dominant plant in the F1 generation if
the parents are homozygous dominant and homozygous recessive?

4. Two guinea pigs - a white male and a black female - are going to be breed. Assume white
to be the recessive allele. If 1/2 of the offspring produced in the cross are white and the
other 1/2 are black, what were the parent’s genotype.
Name _____________________________Date _______________ Period ________

Genetics Practice Problems #6 - ABO Multiple Allele Worksheet 1

Directions: Given the alleles, genotypes and phenotypes for human blood typing ABO, solve
the following multiple allele problems. Recall that A and B alleles are codominant and O is
recessive. A = B > O Phenotypes Genotypes
A IAIA, IAiO
B IBIB, IBiO
AB IAIB
O iOiO

1. What is the expected genotypic ratio among children born to a mother having the
genotype IAiO and a father with the phenotype AB?

2. One parent has the blood type A and the other blood type B. What are the genotypes of
the parents if they produce children with only blood type AB?

3. One parent has the blood type A and the other blood type B. What are the genotypes of
the parents if 1/2 the offspring are AB and the other 1?2 A?

4. One parent has the blood type A and the other blood type B. What are the genotypes of
the parents if 1/2 of the offspring are blood type AB and the other 1/2 blood type A.
5. One parent has the blood type A and the other blood type B. What are the genotypes of
the parents if the offspring produce the following blood types...1/4 AB, 1/4 A, 1/4 B, and
1/4 O?

6. From the following blood types, determine which baby belongs to which parents.

Baby 1 belongs to the _____________ Family

Baby 2 belongs to the ___________ Family

Mrs. Doe.............Type A
Mr. Doe .............Type A
Mrs. Jones ......... Type A
Mr. Jones .......... Type AB
Baby 1 ............. Type O
Baby 2 ............. Type B
Name _____________________________Date _______________ Period ________

Genetics Practice Problems #7 – Sex Linkage Worksheet 1

Directions: Use these genotypic symbols for the sex linked trait of red-green color
blindness in humans to solve the problems that follow. Show your work.

"Normal" female XCXC
Carrier female XCXc
Color-blind female XcXc
Normal male XCY
Color-blind Male Xc Y

1. A normal female marries a color blind male.
(A) What are the chances that the offspring will be color blind if they are females?
(B) What are the chances that the offspring will be color blind if they are males?

A. ____________

B. ____________

2. A color-blind female marries a normal male. How many of the female offspring will be
carries of the color-blind allele?

A. ____________

3. A carrier female marries a normal male.
(A) How many of the the male offspring can be expected to be color-blind?
(B) How many of the the male offspring can be expected to have normal vision?
(C) How many of the the female offspring can be expected to be carriers?
(D) How many of the the female offspring can be expected to be normal?

A. ____________

B. ____________

C. ____________

D. ____________

4. A man whose mother is color blind marries a woman with normal vision. (A) What is the
genotype of the husband? (B) What percent of their offspring can be expected to be color-
blind? (C) What percent of the male offspring can be expected to be color-blind? (D) What
percentage of their offspring can be expected to be carriers?

A. ____________

B. ____________

C. ____________

D. ____________

5. A normal man marries a woman whose mother is a known carrier of a sex-linked recessive
lethal gene on the X chromosome. This gene results in the slow degenerative death of all
male infants within the first year. (A) What are the chances of this couple having a normal
offspring? (B) What are the chances of this couple having a normal male offspring?

A. ____________

B. ____________

Vocabulary Study Guide 01 Key
Alleles - alternate or unlike forms of the same gene. (i.e. Tall and short are alleles for the trait of height in
pea plants)
Back-cross or test-cross - crossing an individual of known genetic make up, a homozygous recessive, with
another of unknown genotype so that its genetic makeup can be determined.

Chromosomes - usually occur in pairs, one set from each parent. They contain bits of information defined as
genes.
Cross Pollination - when pollen from another flower is used to fertilize its eggs.
Dihybrid (two factor) cross - a cross involving two traits. Sometimes called a two-factor cross.

Dominant - the expression of one allele over another. (Tall plant height is dominant over short height in pea
plants.)
Filial - (latin: filius = son) the offspring of a cross. F1 = first generation; F2 = second generation
Gametes - another name for sex cells; eggs and sperm

Gene - discrete units of heredity carried on the chromosomes. (They produce their effect by directing the
manufacture of specific proteins.)

Gene locus - the location or site of a gene on a chromosome. (loci = plural)

Genetics (juh- NET ihks) - the science of heredity
Genotype - the genetic makeup of an individual.

Heterozygous - (heht-er-oh-ZIGH-guhs) possessing two different alleles for a trait. ( i.e. T t )
Heredity - biological inheritance; the genetic makeup of an organism.

Homozygous - possessing two identical alleles for a trait. (i.e. T T = homozygous dominant, t t = homozygous
recessive

Hybrid - an organism with two different alleles for a particular trait. A heterozygote.

Incomplete - alleles which are neither dominant or recessive. They result in a blending in the heterozygous
condition.
Monohybrid (one factor) cross - a cross involving only one trait. Sometimes called a one-factor cross.

Parents - individual crossed to produce offspring. P1 = first parent generation
Pistil - the female reproductive organ of a flower.

Phenotype - the physical appearance of an individual.

Punnett square - a box design used to determine the possible genetic characteristics a cross.
Purebred - belonging to a group of organisms that can produce offspring having one one form of a trait each
genertion.

Probability - the likelihood tat a particular event will occur.
Recessive - an allele which is dominated or suppressed by another. It can only express itself in the absence of
the dominant allele.

Self-pollination - when a flower uses its own pollen to fertilize its eggs.

Stamen - the male reporductive organ of a flower.
Test Cross - see back cross.
Trait - any aspect of an individual described in terms of its characteristics (i.e. hair color, height).