Genetics
Gregor Mendel
• “father of genetics”
• studied pea plants
– genes carry inherited traits
– predicted how traits were inherited
Genetics Vocabulary
• Allele – a section of DNA; you have 2 for every
trait, one from mom and one from dad
• DOMINANT – trait/allele that shows up;
represented by CAPITAL letters
• recessive – trait/allele that is hidden;
represented by lowercase letter
alleles
Genetics Vocabulary
If A stands for
axial flowers and
a stands for
terminal flowers
• genotype – what your DNA says your traits
are; represented by 2 letters (b/c you have 2
alleles for each trait)
or
or
• phenotype – what you see because of the
DNA you have
phenotype=
Axial flowers
phenotype=
Axial flowers
phenotype=
terminal flowers
Practice: Are these genotypes or
phenotypes?
•
•
•
•
•
•
•
Tt
round
black
BB
smooth
rr
tall
Genetics Vocabulary
• homozygous – 2 letters of the same size, same
alleles (pure)
Homozygous
dominant
Homozygous
recessive
• heterozygous – 2 letter of the different sizes,
different alleles (hybrid)
Practice: Are these genotypes
homozygous or heterozygous? If they
are homozygous, are they dominant or
recessive?
•
•
•
•
•
•
AA
Gg
hh
Oo
MM
ss
In pea plants, green pods are completely dominant
over yellow.
What letter will we use?
What are the genotypes?
• Homozygous yellow
• Heterozygous green
gg
Gg
• Pure dominant
• Hybrid
GG
Gg
Punnett Squares
• Punnett Squares: used to predict the possible
genotypes and phenotypes of offspring.
Parent 1
Parent 2
offspring
offspring
offspring
offspring
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Simple Dominance
– Incomplete Dominance
– Codominance
– Sex-linked Traits
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Simple Dominance – one trait
• Use 1 letter and capital or lowercase letters
Ex: In pea plants axial flowers are dominant to
terminal flowers. What would be the result of a
cross between a homozygous dominant pea plant
and a homozygous recessive pea plant?
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using?
What genotypes for the parents?
Parent 1:
Parent 2:
Parent 1
Parent 2
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1:
Parent 2:
Parent 1
Parent 2
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
Parent 1
Parent 2
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
A
A
a
a
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
A
A
a
Aa
a
***Bring the letters
down and over
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
A
A
a
Aa
a
Aa
***Bring the letters
down and over
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
A
Aa
A
a
Aa
a
Aa
***Bring the letters
down and over
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
A
a
Aa
Aa
A
a
Aa
Aa
***Bring the letters
down and over
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
Genotypes:
A
a
Aa
Aa
A
a
Aa
Aa
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
Genotypes:
Aa
4:0
100%
A
a
Aa
Aa
A
a
Aa
Aa
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
Genotypes:
Aa
4:0
100%
A
a
Aa
Aa
A
a
Aa
Aa
Phenotypes:
Ex: In pea plants axial flowers are dominant to terminal flowers. What
would be the result of a cross between a homozygous dominant pea
plant and a homozygous recessive pea plant?
What letter are we using? A
What genotypes for the parents?
Parent 1: AA
Parent 2: aa
Genotypes:
Aa
4:0
100%
A
a
Aa
Aa
A
Phenotypes:
Axial
4:0
100%
a
Aa
Aa
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Simple Dominance
– Incomplete Dominance
– Codominance
– Sex-linked Traits
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Incomplete Dominance: neither allele is
completely dominant over the other, so the
phenotypes BLEND together.
Ex.
Red X
=
PINK
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red:
White:
Pink:
What genotypes for the parents?
Genotypes:
Parent 1:
Parent 2:
Phenotypes:
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red: RR
White: WW
Pink: RW
What genotypes for the parents?
Genotypes:
Parent 1:
Parent 2:
Phenotypes:
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red: RR
White: WW
Pink: RW
What genotypes for the parents?
Genotypes:
Parent 1: RW
R
W
Parent 2: RW
R
Phenotypes:
W
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red: RR
White: WW
Pink: RW
What genotypes for the parents?
Genotypes:
Parent 1: RW
R
W
Parent 2: RW
R
RR
Phenotypes:
W
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red: RR
White: WW
Pink: RW
What genotypes for the parents?
Genotypes:
Parent 1: RW
R
W
Parent 2: RW
R
RR
RW
Phenotypes:
W
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red: RR
White: WW
Pink: RW
What genotypes for the parents?
Genotypes:
Parent 1: RW
R
W
Parent 2: RW
RR
RW
Phenotypes:
W
RW
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red: RR
White: WW
Pink: RW
What genotypes for the parents?
Genotypes:
Parent 1: RW
R
W
Parent 2: RW
R
RR
RW
Phenotypes:
W
RW
WW
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red: RR
White: WW
Pink: RW
What genotypes for the parents?
Genotypes:
Parent 1: RW
RR; RW; WW
R
W
Parent 2: RW
1:2:1
25%:50%:25%
R
RR
RW
Phenotypes:
W
RW
WW
Ex: Snapdragons are flowers controlled by incomplete dominance.
When you cross a red snapdragon with a white snapdragon the results
are pink snapdragons. What would be the cross of 2 pink
snapdragons?
What are the genotypes of red, white, and pink snapdragons?
Red: RR
White: WW
Pink: RW
What genotypes for the parents?
Genotypes:
Parent 1: RW
RR; RW; WW
R
W
Parent 2: RW
1:2:1
25%:50%:25%
R
W
RR
RW
RW
WW
Phenotypes:
Red; Pink; White
1:2:1
25%:50%:25%
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Simple Dominance
– Incomplete Dominance
– Codominance
– Sex-linked Traits
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Codominance – Both alleles are dominant. Both
alleles show up.
Black X
=
C e k r d
Codominance
Codominance
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black:
White:
Checkered:
What genotypes for the parents?
Parent 1:
Genotypes:
Parent 2:
Phenotypes:
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black: BB
White: WW
Checkered: BW
What genotypes for the parents?
Parent 1:
Genotypes:
Parent 2:
Phenotypes:
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black: BB
White: WW
Checkered: BW
What genotypes for the parents?
Parent 1: BW
Genotypes:
Parent 2: BW
B
W
B
Phenotypes:
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black: BB
White: WW
Checkered: BW
What genotypes for the parents?
Parent 1: BW
Genotypes:
Parent 2: BW
B
W
B
BB
Phenotypes:
W
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black: BB
White: WW
Checkered: BW
What genotypes for the parents?
Genotypes:
Parent 1: BW
B
W
Parent 2: BW
B
BB
BW
Phenotypes:
W
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black: BB
White: WW
Checkered: BW
What genotypes for the parents?
Parent 1: BW
Genotypes:
Parent 2: BW
B
W
B
BB
BW
Phenotypes:
W
BW
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black: BB
White: WW
Checkered: BW
What genotypes for the parents?
Genotypes:
Parent 1: BW
B
W
Parent 2: BW
B
BB
BW
Phenotypes:
W
BW
WW
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black: BB
White: WW
Checkered: BW
What genotypes for the parents?
Genotypes:
Parent 1: BW
BB; BW; WW
B
W
Parent 2: BW
1:2:1
25%:50%:25%
B
BB
BW
Phenotypes:
W
BW
WW
Ex: In chickens, feather color is controlled by codominant alleles.
When black chickens are crossed with white chickens, black and white
checkered chickens appear. What is the cross between two checkered
chickens?
What are the genotypes of black, white, and checkered chickens?
Black: BB
White: WW
Checkered: BW
What genotypes for the parents?
Genotypes:
Parent 1: BW
BB; BW; WW
B
W
Parent 2: BW
1:2:1
25%:50%:25%
B
W
BB
BW
BW
WW
Phenotypes:
Black; Checkered;
White
1:2:1
25%:50%:25%
Incomplete or Codominance?
• Red cow crossed with white cow results in
roan cattle. Roan cattle have both red and
white hairs.
• A blue blahblah bird and a white blahblah bird
produce offspring that are silver.
• A certain species of mouse with black fur is
crossed with a mouse with white fur and all of
the offspring have grey fur.
Incomplete or Codominance?
• White chicken x black chicken = black and
white checkered chicken
• A red flower and a white flower produce pink
flowers.
• A black cat and a tan cat produce tabby cats,
cats where black and tan fur is seen together.
• A woman with blood type A and a man with
blood type B have a child with blood type AB
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Codominance – Both alleles are dominant. Both
alleles show up.
– Blood Types
There are 4 blood types:
A, B, AB, and O
AB blood type is codominant
Blood Types
Genotype
Genotype
Phenotype
IAIA or IAi
AA or AO
A
IBIB or IBi
BB or BO
B
IAIB
AB
AB
ii
OO
O
EOC way
Ms. Edmonds way
(easier)
***this problem is not specific so we have to do multiple punnett squares
Ex: What would be the expected outcomes of children between
a man with A blood and a woman with B blood?
What genotypes for the parents?
Parent 1:
Parent 2:
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Simple Dominance
– Incomplete Dominance
– Codominance
– Sex-linked Traits
Genetic Crosses
• There are 4 genetic crosses we will discuss.
– Sex-linked Traits – traits that are determined by
sex (gender). On the X chromosome.
• Males XY
• Females XX
– Examples of sex-linked traits
• Colorblindness
• Hemophilia
Sex-Linked Traits:
•Some genes are found on the sex chromosomes
•Some are found on the X sex chrom. but not the
Y
Ex – the color vision gene is on the X
chromosome
- NOT FOUND ON THE “Y”
Sex-linked traits are RECESSIVE (mostly) traits
that are found on the ‘x’ sex chromosome
Colorblindness Self Test
Can you see the hidden numbers?
Colorblindness Self Test:
NUMBERS: 5 | 8 | 9 | 5 | 3 | 5 | 9 | 10 |
Hidden Shapes:
SHAPES:
Plate 1 - Circle and arch
Plate 2 - Circle, star and square
Hemophilia
Pedigree of Queen Victoria
Hypertrichosis –
Human Werewolf Syndrome:
Congenital generalized hypertrichosis (CGH)
Rare, X-linked dominant trait
Found in a single multigenerational Mexican
family
Why do males go bald???
•Females have 2 X chromosomes so they can be
“carriers” for the sex-linked trait but their
phenotype is the normal condition
•One of the chromosomes can “mask” the sexlinked trait
•Males have only 1X chromosome so if they get
the recessive trait that is a sex-linked trait, then
they will show it.
Sex-Linked Genotypes/Phenotypes
Phenotype
Male
Female
Genotype
Genotype
Normal
XH Y
X HX H
Affected
XhY
X hXh
Carrier
None
X HX h
Ex: If a man with hemophilia marries a woman whose father was a
hemophiliac, what are the possible genotypes and phenotypes of their
children?
Man:
Woman:
What genotypes for the parents?
Man:
Woman:
Genotypes:
Phenotypes:
Ex: If a man with hemophilia marries a woman whose father was
hemophiliac, what are the possible genotypes and phenotypes of their
children?
Man: hemophilia
Woman: father was hemophiliac which makes her a carrier
What genotypes for the parents?
Man:
Woman:
Genotypes:
Phenotypes:
Ex: If a man with hemophilia marries a woman whose father was
hemophiliac, what are the possible genotypes and phenotypes of their
children?
Man: hemophilia
Woman: father was hemophiliac which makes her a carrier
What genotypes for the parents?
h
Man: X Y
H h
Woman: X X
Genotypes:
Phenotypes:
Ex: If a man with hemophilia marries a woman whose father was
hemophiliac, what are the possible genotypes and phenotypes of their
children?
Man: hemophilia
Woman: father was hemophiliac which makes her a carrier
What genotypes for the parents?
h
Man: X Y
H h
Woman: X X
h
X
X
X
H
h
Genotypes:
Y
Phenotypes:
Ex: If a man with hemophilia marries a woman whose father was
hemophiliac, what are the possible genotypes and phenotypes of their
children?
Man: hemophilia
Woman: father was hemophiliac which makes her a carrier
What genotypes for the parents?
h
Man: X Y
H h
Woman: X X
h
X
Y
H
X HX h
X HY
h
XhXh
XhY
X
X
Genotypes:
Phenotypes:
Ex: If a man with hemophilia marries a woman whose father was
hemophiliac, what are the possible genotypes and phenotypes of their
children?
Man: hemophilia
Woman: father was hemophiliac which makes her a carrier
What genotypes for the parents?
h
Man: X Y
H h
Woman: X X
h
X
Y
XHXh; XhXh; XHY; XhY
Phenotypes:
H
X HX h
X HY
h
XhXh
XhY
X
X
Genotypes:
1:1:1:1
25%: 25%: 25%: 25%
Ex: If a man with hemophilia marries a woman whose father was
hemophiliac, what are the possible genotypes and phenotypes of their
children?
Man: hemophilia
Woman: father was hemophiliac which makes her a carrier
What genotypes for the parents?
h
Man: X Y
H h
Woman: X X
h
X
Y
H
X HX h
X HY
h
XhXh
XhY
X
X
Genotypes:
XHXh; XhXh; XHY; XhY
1:1:1:1
25%: 25%: 25%: 25%
Phenotypes:
Carrier girl
hemophiliac girl
Normal boy
hemophiliac boy
1:1:1:1
25%: 25%: 25%: 25%
Pedigrees
• Shows a pattern of inheritance in a family for a
specific trait (phenotype)
• Genotypes can usually be determined
• Why would we want to use a pedigree in genetics?
• Track the occurrence of diseases such as:
–
–
–
–
Huntington’s – simple dominant – lethal allele – causes breakdown of the brain
Cystic fibrosis – 1/2500 – mucus accumulates (white North Amer.)
Tay-Sachs disease – lipids accumulate in CNS (Jewish)
Phenylketonuria – missing enzyme causes problems in CNS (Nordic/Swedish)
Pedigree of Queen Victoria
Pedigree Analysis
Have you ever seen a family tree… do you have one??
Graphic representation of family inheritance.
The Symbols used:
Sample pedigree:
•generations are numbered with Roman Numerals
•oldest offspring are on the left
• How many males are
present? How many
females?
• How many females show
the trait being studied?
• What is the sex of
offspring III-9?
• How many offspring did
the generation I parents
have?
• What is the difference
between the II-3 & 4 and
IV-2 & 3?
Inheritance patterns:
• Autosomal dominant:
The disease is passed from the father
(II-3) to the son (III-5), this never
happens with X-linked traits.
The disease occurs in three
consecutive generations, this never
happens with recessive traits.
Males and females are affected, with
roughly the same probability.
–Examples: Polydactyly
–Huntington’s disease
Inheritance patterns:
• Autosomal recessive
Males and females are equally likely to be
affected.
The recurrence risk to the unborn sibling of an
affected individual is 1/4.
The trait is characteristically found in siblings,
not parents of affected or the offspring of
affected.
Parents of affected children may be related. The
rarer the trait in the general population, the
more likely a consanguineous mating is involved.
–Cystic fibrosis
–Tay-Sach’s disease
Inheritance patterns:
• Sex-linked recessive conditions
The disease is never passed from father to
son.
Males are much more likely to be affected
than females.
•All affected males in a family are related
through their mothers.
–Examples:
Trait or disease is typically passed from an
affected grandfather, through his carrier
daughters, to half of his grandsons.
–Color-blindness
–Hemophilia
–Duchenne Muscular Dystrophy
The Ultimate Pedigree Challenge
• https://migrc.org/Library/UltimatePedigreeCh
allengeResources.html
• Take out a sheet of paper/or sketch this in
your notes.
• Listen to the song and make a pedigree of the
singer and his family. Use the lyrics to help
you.
Making Your Own Pedigree!
• Sketch out on notebook paper your own family
pedigree
• Must include at least 3 generations or 15 people
[grandparents, parents (with aunts, uncles, etc.) and you
(brothers, sisters, cousins)]
• Choose one trait that you have and track that
trait with as many members of your family as you
can (label the genotypes that you know)
– Keep your trait simple. EXAMPLES, MORE EXAMPLES
• Your final pedigree must be on computer or
construction paper!
Pedigree Project Rubric (25 points)
5
4-3
2-1
0
Correctness
/5
Neatness
/5
Presentation
/5
Title and Key
/5
Labeled Genotypes
/5
Total =
To get a 5:
Correctness – All aspects of the pedigree are correct. Symbols used
appropriately. Pedigree is numbered appropriately.
Neatness – Pedigree is neat and colorful.
Presentation – Pedigree is on final paper.
Title and Key – Title and Key are present and located on the front of the
paper next to the pedigree
Labeled Genotypes – You, any siblings, and biological parents possible
genotypes are listed next to individual or in the key.
/25