Download complex patterns of inheritance

Cross a homozygous dominant
green plant with a heterozygous
green plant. What are the genotypic
and phenotypic ratios.
Agenda for Tuesday Jan 3rd
1. Test stuff
2. Lab
Cross 2 heterozygous green pea
seed plants. What is the chance to
have a yellow (recessive trait) pea
seed?
Agenda for Wednesday Jan 4th
1. Complex patterns of inheritance
– Incomplete and Co-dominance
Quiz Monday
Complete Dominance
• a heterozygous individual’s phenotype will show
dominant trait
Purebred red snapdragons were crossed with
purebred white snapdragons all offspring were pink
Incomplete Dominance
• one allele for a trait is not completely dominant
over the other allele
• Combined phenotype (blended)
R = allele for red flowers
W = allele for white flowers
red x white ---> pink
RR x WW ---> 100% RW
Co-dominance
• In COdominance, the "recessive" & "dominant"
traits appear together in the phenotype of
hybrid (heterozygous) organisms
Practice
Set up genotypes for the phenotypes listed in each
set. Remember that the "medium" trait is always
heterozygous.
a) Birds can be blue, white, or white with blue-tipped
feathers.
b) Flowers can be white, pink, or red.
c) A Hoo can have curly hair, spiked hair, or a mix of
both curly and spiked.
D) A person can be tall, medium, or short.
1. Write the genotypes for the pictured phenotypes
2. Show the cross between a star-eyed and a circle
eyed.
What are the phenotypes of the offspring?
What are the genotypes?
3. Show the cross between a circle-star eyed, and a
circle eyed.
How many of the offspring are circle-eyed?
How many of the offspring are circle-star eyed?
Write the genotypic and phenotypic ratios.
4. Show the cross between two circle-star eyed.
How many of the offspring are circle-eyed?
How many of the offspring are circle-star eyed?
How many are star eyed?
In humans, straight hair (SS) and curly hair (CC) are
co-dominant traits that result in hybrids that have
wavy hair (SC). Cross a Straight hair female with a
wavy haired male.
What are the chances of having a curly haired child?
What are the chances of having a straight hair child?
What are the chances of having a wavy hair child?
Agenda for Thursday Jan 5th
1. Sex Linked traits
Quiz Monday – incomplete/codominance/sex
linked traits/multiple alleles
Sex Determination
• Thomas Hunt Morgan – studied fruit flies in
the early 1900’s
Sex Determination
• Observed that one pair of chromosomes was
different between males and females
– Large one named “X” chromosome
– Smaller one named “Y” chromosome
– XX = female; XY = male
XY
X
XX
Y
X
Y
X
X
X
X
XX
XX
Female
Female
XY
XY
Male
Male
50% Female; 50% Male
Sex Linkage
• Sex Linkage: the presence of a gene on a
sex chromosome (X or Y)
• X-linked genes: genes found on the X
chromosome
– X chromosome carries more genes
• Y-linked genes: genes found on the Y
chromosome
Fruit Fly Eye Color
• Fruit flies normally have red eyes
– Red is dominant; white is recessive
• A few males have white eyes
Morgan’s Fruit Fly Experiments
• Red-eyed female (XRXR) x White-eyed male (XrY)
XR
Xr
XRXr
XRXr
RESULTS:
F1 generation –
red-eyed
XRY
Y
XR
XRY
all
Morgan’s Fruit Fly Experiments
• Red-eyed female (XRXr) x Red-eyed male (XRY)
XR
XR
XRXR
XRY
Y
Xr
XRXr
XrY
RESULTS:
F2 generation –
3
red-eyed and 1 whiteeyed
** all white-eyed where
males…why?
Morgan’s Conclusions
• Gene for eye color is carried on the X
chromosome = eye color is an X-linked trait
• Y chromosome does not carry a gene for eye
color
• Red-eyed = XRXR, XRXr , XRY
• White-eyed = XrXr, XrY
In humans colorblindness (b) is an example of a
sex-linked recessive trait. A male without
colorblindness marries a female who isn’t
colorblind but carries the allele.
1. What are the phenotypes of the offspring?
2. What are the genotypes of the offspring?
3. What are the genotypic ratios?
4. What are the phenotypic ratios?
5. What is the percent chance of each genotype?
6. What is the percent chance of each phenotype?
In fruit flies red eye color (R) is dominant to white
eyes (r) and is a sex linked trait.
A heterozygous red eye female mates with a red
eye male.
1. What are the phenotypes of the offspring?
2. What are the genotypes of the offspring?
3. What are the genotypic ratios?
4. What are the phenotypic ratios?
5. What is the percent chance of each genotype?
6. What is the percent chance of each phenotype?
In fruit flies red eye color (R) is dominant to
white eyes (r). Cross a heterozygous female with
a white eye male. What are the phenotypic and
genotypic ratios?
Agenda for Friday Jan 6th
1. Practice with sex linked traits
2. Multiple alleles
Quiz Tuesday
In fruit flies red eye color (R) is dominant to
white eyes (r) and is a sex linked trait.
A heterozygous red eye female mates with a
white eye male.
How many males will have white eyes?
In humans colorblindness (b) is an example of a
sex-linked recessive trait. A male with
colorblindness marries a female who isn’t
colorblind and does not carry the allele.
What is the chance they will have a child that is
colorblind?
Multiple Alleles
• Multiple alleles – traits
determined by more
than 2 alleles
– Increases possible
number of genotypes &
phenotypes
• We have 2 alleles (1 from
mom, 1 from dad)
– Blood groups (ABO), O is
recessive (i allele)
ALLELE
IA
IB
i
CODES FOR
Type "A" Blood
Type "B" Blood
Type "O" Blood
GENOTYPES
IAIA
IAi
RESULTING PHENOTYPES
Type A
Type A
IBIB
IBi
Type B
Type B
IAIB
Type AB
ii
Type O
• More alleles means more combinations
• there are 6 different genotypes & 4 different phenotypes
for blood type
• 2 genotypes for both "A" & "B" blood --- either homozygous
(IAIA or IBIB) or heterozygous with one recessive allele for "O"
(IAi or IBi).
• The only genotype for "O" blood is homozygous recessive (ii).
• And lastly, what's the deal with "AB" blood? What is this an
example of? The "A" trait & the "B" trait appear together in
the phenotype.
Problems
• A woman with Type O blood and a man who is Type
AB have are expecting a child. What are the possible
blood types of the kid?
• What are the possible blood types of a child who's
parents are both heterozygous for "B" blood type?
One More
• What are the chances of a woman with Type
AB and a man with Type A having a child with
Type O?
What are the chances of a woman with Type AB
and a man with Type O having a child with
Type O?
Agenda for Monday Jan 9th
1. Review
2. Video
Quiz Tomorrow
What are the chances of a woman
with Type AB and a man with Type
AB having a child with Type A?
Agenda for Tuesday Jan 10th
1. Quiz
2. Breeding styrofoam monsters Lab
Quiz/test Friday
Epistasis
• Epistasis – one allele hides/suppresses another allele
Polygenic
• Phenotype depends on alleles in multiple
genes
– Skin color, height, eye color
– Continuous progression in expression of traits