Non mendelian problems
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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

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Non mendelian problems

Non-Mendelian Problems


I sex linked traits

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

fruit fly

eye color

Xy chromosome – male

-the trait will be determined

by the gene on the X, none

On the Y

XX chromosome - female

Sex-linked Traits

Example: Eye color in fruit flies

Sex Chromosomes


Sex linked trait problem

Xr

Xr

XR

Y

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 does not carry traits.

  • RR = red eyed

  • Rr = red eyed

  • rr = white eyed

  • XY = male

  • XX = female


Non mendelian problems

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

Sex-linked Trait Solution:

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

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

Female Carriers

*1/2 filled in box=carrier, filled in box=affected individual


Incomplete dominance

Incomplete Dominance


Incomplete dominance1

W

W

R

R

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. Red=RR, white=WW Pink=RW

  • Ex:snapdragons (flower)

  • red (RR) x white (WW)

  • RW=pink flower

  • RR = red flower

  • WW = white flower

*Fill in the square to the left


Incomplete dominance2

W

produces the

F1 generation

RW

RW

R

R

RW

RW

Genotypic Ratio:

0:4:0—100%RW

Phenotypic Ratio:

0:4:0—100%pink

Incomplete Dominance

W


Incomplete dominance problem

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 P1, do the Punnett Square, and give the genotypic and phenotypic ratios for F1 generation of this cross.


P 1 rr x rw

P1 = __RR__ x __RW__

Genotypic ratio: ____ : _____ : _____

Phenotypic ratio: ____ : _____ : _____


P 1 rr x rw1

P1 = __RR__ x __RW__

R

W

R

RR

RW

RW

R

RR

2

2

0

or 50%RR,50%RW

Genotypic ratio: ____ : _____ : _____

2

2

0

or 50%RED,50%ROAN

Phenotypic ratio: ____ : _____ : _____


Incomplete dominance3

Incomplete Dominance


Dihybrid cross

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

Question:How many gametes will be produced for the following allele arrangements?

  • Remember:2n (n = # of heterozygotes)

  • 1.RrYy

  • 2.AaBbCCDd

  • 3.MmNnOoPPQQRrssTtQq


Answer

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 cross1

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 cross2

RY

Ry

rY

ry

RY

Ry

rY

ry

Dihybrid Cross


Dihybrid cross3

RY

Ry

rY

ry

Round/Yellow: 9

Round/green: 3

wrinkled/Yellow: 3

wrinkled/green: 1

RY

RRYY

RRYy

RrYY

RrYy

Ry

RRYy

RRyy

RrYy

Rryy

rY

RrYY

RrYy

rrYY

rrYy

ry

RrYy

Rryy

rrYy

rryy

9:3:3:1 phenotypic ratio

Dihybrid Cross


Dihybrid cross4

Dihybrid Cross

Round/Yellow: 9Round/green: 3wrinkled/Yellow: 3wrinkled/green: 1

9:3:3:1


Codominance

CODOMINANCE


Multiple alleles 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

IA

i

IAIB

IBi

IB

Genotypic ratio:

50% IAIB

Phenotypic ratio:

50% type AB

50%= IBi

50%= type B

IB

IAIB

IBi

Codominance Problem

  • Example:Cross a male who is homozygous Type B (BB) x a female that is heterozygous Type A (AO)


Another codominance problem

IA

IB

i

i

Another Codominance Problem

  • Example: Cross a

  • male Type O (ii) x female type AB (IAIB)

*Give the genotypic and phenotypic ratios of the offspring


Another codominance problem1

IA

IB

IAi

IBi

i

Genotypic Ratio:

50% IAi

Phenotypic Ratio:

50% type A

50% IBi

50% type B

i

IAi

IBi

Another Codominance Problem

  • Example:male Type O (ii) x female type AB (IAIB)


Codominance1

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)


Codominance2

IA

i

IAIB

IB

i

ii

Codominance

  • Answer:

Parents:

genotypes = IAi and IBi

phenotypes = A and B


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