Download 2014 Non-Mendelian Problems

Non-Mendelian Problems
I Sex-linked Traits
• These are Traits (genes) that are located on
the sex chromosomes.
• Sex chromosomes are X and Y
• XX genotype for females
• XY genotype for males
• Many sex-linked traits are carried on X
chromosome of the sex chromosomes
• That is why these genetic disorders are
found mainly in males, there is no gene for
this trait on the Y chromosome to cancel out
a bad gene on the X chromosome
Sex-linked Traits
Example: Eye color in fruit flies
Sex Chromosomes
fruit fly
eye color
XX chromosome - female
Xy chromosome – male
-the trait will be determined
by the gene on the X, none
On the Y
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Sex-linked
Trait
Problem
Use the same principles used in the
Mendelian Monohybrid problems, except that
the sex of the offspring must be included
and the Y chromosome will not have an
allele
Example: Eye color in fruit flies
(red-eyed male) x (white-eyed female)
XRY
x
XrXr
Remember: the Y chromosome in males Xr
does not carry traits.
RR = red eyed
Rr = red eyed
XR
rr = white eyed
XY = male
Y
XX = female
Xr
POSSIBLE GENOTYPES IN SEX-LINKED
PROBLEMS:
XRXR—FEMALE w/ HOMOZYGOUS DOM
XRXr—FEMALE w/ HETERZYGOUS
XrXr—FEMALE w/ HOMOZYGOUS REC
XRY—MALE w/ DOM ALLELE
XrY—MALE w/ REC ALLELE
Sex-linked Trait
Solution:
Xr
Xr
XR
XR Xr XR Xr
Y
Xr Y
Xr Y
Genotypic Ratio:
50% XR Xr
50% Xr Y
Phenotypic Ratio:
50 % white eyed male
50 % red eyed female
Sex-linked Cross ?s from previous
problem
1. What % of the males will be red eyed?
2. What % of the offspring will be red eyed?
3. What % of the offspring will be males?
4. What % of the females will be white
eyed?
5. What % of the females will be red eyed?
6. What % of the offspring will be white
eyed?
Female Carriers
*1/2 filled in box=carrier, filled in box=affected individual
Incomplete
Dominance
Incomplete Dominance
• F1 hybrids have an appearance somewhat in
between the phenotypes of the two parental
varieties. There is a mixing of the two traits,
neither is dominant over the other. Worked
like Monohybrid problems except that you will
use all capitals letter for each trait, ex.
W
Red=RR, white=WW Pink=RW W
*Fill in
• Ex: snapdragons (flower)
the
R
• red (RR) x white (WW)
square
to the
• RW=pink flower
left
R
• RR = red flower
• WW = white flower
Incomplete
Dominance
W
W
R RW
RW
R RW
RW
produces the
F1 generation
Genotypic Ratio:
0:4:0—100%RW
Phenotypic Ratio:
0:4:0—100%pink
Incomplete Dominance Problem:
• In cattle when a red bull(RR) is mated with
white(WW) cow the offspring are
roan(RW) a blending of red and white.
Mate a red bull with a roan cow. Use the
format on the next slide and give the P , do
the Punnett Square, and give the
genotypic and phenotypic ratios for F
generation of this cross.
1
1
P1 = __RR__ x __RW__
Genotypic ratio: ____ : _____ : _____
Phenotypic ratio: ____ : _____ : _____
P1 = __RR__ x __RW__
R
W
R
RR
RW
R
RR
RW
2
2
0
or 50%RR,50%RW
2
2
0
or 50%RED,50%ROAN
Genotypic ratio: ____ : _____ : _____
Phenotypic ratio: ____ : _____ : _____
Incomplete Dominance
Dihybrid Cross
• A breeding experiment that tracks the
inheritance of two traits.
• Mendel’s “Law of Independent
Assortment”
• a. Each pair of alleles segregates
independently during gamete formation
• b. Formula: 2n (n = # of heterozygotes)
Question:
How many gametes will be produced
for the following allele arrangements?
• Remember: 2n (n = # of heterozygotes)
•
1.
RrYy
•
2.
AaBbCCDd
•
3.
MmNnOoPPQQRrssTtQq
Answer:
1. RrYy: 2n = 22 = 4 gametes
RY
Ry
rY ry
2. AaBbCCDd: 2n = 23 = 8 gametes
ABCD ABCd AbCD AbCd
aBCD aBCd abCD abCD
3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64
gametes
Dihybrid Cross
• Traits: Seed shape & Seed color
• Alleles: R round
r wrinkled
Y yellow
y green
•
RrYy x RrYy
RY Ry rY ry
RY Ry rY ry
All possible gamete combinations by
FOIL method
Dihybrid Cross
RY
RY
Ry
rY
ry
Ry
rY
ry
Dihybrid Cross
RY
RY RRYY
Ry RRYy
rY RrYY
ry
RrYy
Ry
rY
ry
RRYy
RrYY
RrYy
RRyy
RrYy
Rryy
RrYy
rrYY
rrYy
Rryy
rrYy
rryy
Round/Yellow:
Round/green:
9
3
wrinkled/Yellow: 3
wrinkled/green:
1
9:3:3:1 phenotypic
ratio
Dihybrid Cross
Round/Yellow: 9
Round/green:
3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1
CODOMINANCE
Multiple Alleles /Codominance
• Non-Mendelian Cross where 2 alleles are
expressed (multiple alleles) in heterozygous
individuals.
• Example: blood type
Use the genotypes below whenever doing blood
type crosses.
•
1.
type A
= AA -pure or AO -hybrid
•
2.
type B
= BB -pure or BO -hybrid
•
3.
type AB = AB -codominant
•
4.
type O
= OO -pure
Codominance
Problem
• Example: Cross a male who is
homozygous Type B (BB) x a female that
is heterozygous Type A (AO)
IA
i
IB
IAIB
IBi
IB
IAIB
IBi
Genotypic ratio:
50% IAIB
50%= IBi
Phenotypic ratio:
50% type AB
50%= type B
Another Codominance Problem
• Example: Cross a
male Type O (ii)
x
female type AB (IAIB)
IA
i
i
IB
*Give the
genotypic and
phenotypic ratios
of the offspring
Another Codominance
Problem
• Example: male Type O (ii)
x
female type AB (IAIB)
IA
i
IAi
i
IAi
IB
IBi
IBi
Genotypic Ratio:
50% IAi
50% IBi
Phenotypic Ratio:
50% type A
50% type B
Codominance
• Question:
If a boy has a blood type O and
his sister has blood type AB,
What are the genotypes and
phenotypes of their parents?
• boy - type O (ii) X girl - type AB
(IAIB)
Codominance
• Answer:
IA
IB
i
i
IAIB
ii
Parents:
genotypes = IAi and IBi
phenotypes = A and B