1. Tongue rolling
2. Hair on second knuckle
3. Widow’s peak
4. Thumb crossing
5. Attached \ unattached ear lobes
6. Crooked finger
A. Genetics is the
study of heredity
B. Heredity is the
passing of traits
from parents to
monk who studied
garden pea plants in
Why a pea plant?
1. True breeding
2. Reproduce quickly & in large numbers.
3. Easy to grow
D. Mendel chose to cross pollinate
Pollination-pollen is dispersed and makes its
way to the female portion of a flower
Fertilization is when the pollen unites with
the ovule to form a zygote.☺
Pistil or (Carpel) is the female portion of the
flower. It consists of:
3) Ovary-contains ovules (eggs)
If fertilized, the ovules
develop into seeds.
The ovary develops
The male portion of the flower is called the
The stamen is composed of:
1. Anther-where the pollen is produced.
1. 1st cross: true
breeding tall plants
(TT) with short
P1 or parental
2. Offspring (called F1
or first generation)
of this cross were
3. 2nd cross: 2
plants of the
4. results were
¾ tall and ¼
This crossing of
one trait is
A. Mendel thought that
inheritance of traits
B. one factor could
mask or hide the
1. Genes are segments
of DNA on a
code for a trait. Each
trait is coded for by
C. Mendel’s ―factors‖ are the alleles. Alleles are
alternate forms of the same gene.
Ex-color of flower is a trait
The alleles for flower color in pea plants are
purple or white☺
Some alleles are dominant (they are expressed over a
Other alleles are recessive (they are not expressed when a
dominant allele is present)
a) Recessive alleles are ONLY expressed if the
organism has 2 recessive alleles
Capital letters are used for dominant alleles and lower
case for recessive alleles.
Ex- B means brown fur
b means white fur☺
Genotype- Definition Phenotype-
combo of physical
BB Homozygous Brown fur
Bb Heterozygous Brown fur
bb Homozygous White fur
A. Organisms inherit one allele from each parent
B. Each organism has 2 alleles per trait.
C. The alleles can be the same or different
D. During meiosis, the paired alleles for each trait
separate and end up in different gametes
Meiosis and the
Separation of alleles
•What are the alleles
for the flower?
•What is the dominant
•What is the recessive
•What genes would be
present in the
•Are the parents
•How many alleles are
donated to each gamete?
•How many ways could
the gametes combine?
•How many offspring will
A. Patterns of only one trait are studied.
B. One allele from the female gamete is combined
with one allele from the male gamete.
C. Pairs can be homozygous (pure) or
D. Heterozygous (hybrid)
E. Genotype is the gene combination – BB,Bb,bb
F. Phenotype is physical appearance
G. To determine if an organism is pure or hybrid,
conduct a test cross with a homozygous
Laws of probability can be used to predict
Probability is the chance that a certain event will occur.
A. Shows all possible genotypes
B. Probability predicts what is most likely to
C. But actual outcome may be different.
D. Each outcome is NOT influenced by previous
The Punnett Square is a
all possible gene
combinations for a
Step 1: Assign letters for the traits
B= brown b= white
Step 2: Write the cross
Brown Bb x White bb
Step 3: Set up and work the Punnett square
Step 4: State the genotype ratio and the phenotype
1. Probability is given as a ratio, fraction, or percentage.
2. Ratio-number of offspring that have a particular gene
or trait versus the number of offspring that have
another gene or trait. 3:1
3. Fraction-shows the predicted number of offspring
having a particular trait over the total number of
possible outcomes. ¾ tall to ¼ short
4. Percentage-calculated from fractions 75% tall to 25%
1. What do the letters inside the square represent?
2. What does a correctly completed Punnett square tell
3. Does the probability predict the actual outcome?
4. Is the outcome of a cross affected by previous crosses?
5. Who was Gregor Mendel?
6. What is a monohybrid cross?
7. What are alleles?
8. What does it mean if an organism is heterozygous?
9. What is the only way a recessive trait will be expressed?
A heterozygous tall pea plant is crossed with a
homozygous short pea plant. A Punnett
square predicts that the probability that the
offspring of this cross will 50% tall and 50%
short . In a classroom experiment, student
tested this prediction with four seeds obtained
from this cross
. The first three offspring from this produced
all tall plants. How is this possible? What is
the probability that the fourth offspring will be
Two heterozygous tall pea plants are crossed.
They produced 16 seeds. How many of those
seeds will likely result in short plants?
Phenylketonuria or PKU, is an inherited
disease caused by a recessive allele. If baby has
PKU and is untreated, a certain amino acid
builds up in the tissues and causes severe
mental retardation. If treated, the child can
A young couple has decided that they want to start
their family. David is 28 years old and has been
promised a promotion in his company that will gave
him a better position and more benefits, as well as a
larger salary. He has phenylketonuria, or PKU. His
mother and one sister also have PKU. His wife Trevon
is 25 years old and has an aunt with PKU. She also had
two grandparents with phenylketonuria although
neither of her parents had it. David and Trevon want
to know what their chances are of having a child with
Trevon’s possible phenotypes: _____ or _____
What are the possible genotypes and
phenotypes of their future children?
What is the probability that their children will
NOT have PKU?
A. Often called blending.
B. Neither allele is dominant over the other.
C. Third phenotype is intermediate between the
dominant and recessive ( Ex-four o’clock
flowers white X red = pink)
D. When making a Punnett Square for incomplete
dominance, use 2 different capital letters (RR
for red and WW for white, RW is pink)
How to determine if there is incomplete
dominance? Three different phenotypes, one
of which is a blend.
When homozygous dominant are crossed with a
homozygous recessive, all F1 are intermediate,
while the F2 have a 1:2:1 phenotypic ratio.
A. Both alleles are expressed equally.
B. Codominant alleles are designated with
uppercase letters for each allele and a
superscript may be used.
Example = white
chicken X black
( FWX FB = FWFB)
This causes the 1. hemoglobin in the red blood
cells to be the 2. wrong shape. Hemoglobin is
the protein that carries the oxygen. People who
are homozygous 3. recessive for the allele have
very serious health problems.
E. Roan color
in cattle and
both 1. red
together or Blue
2. black & Roan
1. A trait for snapdragon flower color is
controlled by incomplete dominance. A
snapdragon plant with red flowers is crossed
with a snapdragon plant with white flowers.
What percent of the offspring will have pink
2. If two snapdragon plants with pink flowers
are crossed, what percent of offspring would
you predict as also having pink flowers?
3. A pink snapdragon plant is crossed with a
red snapdragon plant. What percent of the
offspring can be predicted to have white
4. Cross a red horse crossed with a roan
colored horse. List the possible genotypes and
A. Traits controlled by more than 2 alleles.
B. Only two alleles for each individual, but there
are more than 2 alleles for the trait found in a
general population. (in gene pool)
C. Example ABO blood type in humans and
D. coat color in rabbits
There are three alleles for blood type
1. Type A ( IA) , 2. Type B (IB ) and 3. Type O (ii)
4. IA and IB are codominant to each other
5. Both IA and IB are dominant over i, which is
6. Blood typing is important because a person would
die if the wrong type of blood was given. It is also
used to determine who’s NOT ―Yo’ Daddy!‖
Pope Innocent VII-
attempted the first
He drained the
blood of three 10
yr old boys into the
mouth of Pope
Innocent VII. They
Dr. Jean Baptiste Denys-1667
1st successful transfusion – poured about 12 oz
of sheep’s blood into a 15 yr old boy. The boy
lived probably because so little blood actually
made it into the boys blood stream
It was not until the 4 basic blood types were
identified that transfusions could be done
WWII blood trans-
If a child has type AB blood and the mother has type
A blood, could a man with type O blood be the
A mother has type A blood and a father has type B
blood. Can they have a child with type O blood?
Why or why not?
A woman with Type AB blood marries a man with
homozygous Type O blood . What would the blood
type of their children be?
A woman with heterozygous Type A blood (IAI)
marries a man with homozygous Type B blood (IBIB).
What blood type could their children NOT have?
A. Traits are inherited independently.
B. Law is always true IF genes for traits are located on different
During meiosis, alleles for different traits assort independently from
c. For example, seed color has no effect on plant height.
Each parent will donate half of their alleles to
FOIL – F the first letters of the genotype
O the outside letters of each genotype
I the inner letters of the genotype
L the last letters of the genotype
Example: mother is FfWW
possible gametes – FW,FW,fW,fW
Father is FfWw
possible gametes – FW,Fw,fW,fw
FW FW fW fW
A. IF genes for a trait are on the same
chromosome, they may be linked.
B. Inherited together
C. Discovered by Thomas Hunt Morgan (early
D. Studied Drosophila or the fruit fly
• Early studies of crossing over were performed using
the fruit fly Drosophila
Wild type Variant
(gray body, long (black body, short
wings, red eyes) wings, cinnabar eyes)
• Inheritance patterns of a sex-linked gene
Female Male Female Male Female Male
XRXR XrY XRXr XRY XRXr XrY
All females inherit
two X chromosomes,
one from each parent.
All males inherit Female Female
one X chromosome,
always from the R = red-eye allele
mother. r = white-eye allele Male Male
(a) Homozygous red-eyed female white- (b) Heterozygous female red- (c) Heterozygous female white-
eyed male eyed male eyed male
A. Humans have 23 pairs of chromosomes.
1. Autosomes are 22 matching
2. Sex chromosomes make up the 23rd
a. X and Y are the sex chromosomes
b. XX is a female and XY is a male
E. Traits found on the sex chromosomes
1. A male with a recessive trait on the X
chromosome will always ―have it‖ because
there is only one X.
A. Hemophilia is an example of a sex-linked trait
that is passed from mother to son, but not
necessarily from father to daughter.
B. X chromosomes are larger and carry more
genes than Y chromosomes.
C. Red-green colorblindness is another example
1. Organisms that have two identical alleles for the
same trait are called—
2. Both hemophilia and red-green color blindness are
examples of disorders that are—
3. A couple has two children, both girls. What is the
chance that the parents’ next child will be a boy?
4. A Punnett square shows---
5. Where are most the sex-linked genes located?
6. What is the genotype of a female?
7. The type of inheritance that produces roan color is
8. If the recessive trait is expressed as the phenotype,
what would the genotype be?
A. Pedigree is a diagram used to show genetic
B. Male is represented by a square and a female is
represented by a circle.
C. Each horizontal row represents one generation
labeled with Roman numerals.
D. Line connecting male & female means they are
Figure 14-3 A Pedigree
A circle represents A square represents
a female. a male.
A vertical line and
A horizontal line connecting a bracket connect
a male and female the parents to their
represents a marriage. children.
circle or square A circle or
indicates that a square that is
person is a carrier not shaded
of the trait. indicates that
A completely neither
shaded circle or expresses the
square indicates trait nor is a
that a person carrier of the
expresses the trait.
In the pedigree above, determine the
genotypes of the parents in the P1 generation.
In the F1 generation, the one affected daughter
has three children with an unaffected man.
Their two sons are affected with color
blindness. What is the chance of another son
having the disorder?
A. Type of Mutations
1. Gene Mutations-Changes in only one
gene that codes for one protein
a. Substitution-One nucleotide is
substituted or replaced by
1) Point Mutation
Normal: THE RAT HID AND THE CAT SAT
AND GOT FAT.
Substitution: THE PAT HID AND THE CAT SAT
AND GOT FAT.
This will change only one word or in this case one
amino acid in the protein chain.
b. Insertion-One nucleotide is added to
1) Called a frame-shift mutation.
Normal: THE RAT HID AND THE CAT SAT
AND GOT FAT.
Insertion: THE RAT HIX DAN DTH ECA TSA
TAN DGO TRA T
This throws off the whole message from the point
of insertion on. This will more than likely
change the amino acid sequence and the whole
c. Deletion-A nitrogen base is omitted.
1) Another type of frame-shift
Normal: THE RAT HID AND THE CAT SAT
AND GOT FAT.
Deletion: The RAH IDA NDT HEC ATS ATA
NDG OTF AT.
The words or amino acid sequence is changed
from the point of deletion.
2. Chromosomal mutation-structure or number of
a. Duplication-part of chromatid is
b. Deletion-part of chromatid is missing
c. Inversion-broken part reattaches backward
d. Translocation-part of a chromatid attaches
to a different chromosome
used to identify
This is a method in which fragments of DNA are
separated by electric charge and size on a gel
with the smallest fragments traveling the