Incomplete Dominance

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Incomplete Dominance: The heterozygous genotype produces a phenoytype that falls in between the dominant trait and the recessive trait. Incomplete Dominance

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Incomplete Dominance. Incomplete Dominance: The heterozygous genotype produces a phenoytype that falls in between the dominant trait and the recessive trait. Example: - PowerPoint PPT Presentation

Transcript of Incomplete Dominance

Page 1: Incomplete Dominance

Incomplete Dominance: The heterozygous genotype produces a phenoytype that falls in between the dominant trait and the recessive trait.

Incomplete Dominance

Page 2: Incomplete Dominance

Example:

In flowers, petal color demonstrates incomplete dominance. Red results when a flower has homozygous dominant alleles for the trait. White results when a flower has homozygous recessive alleles for the trait. A flower that is heterozygous for this trait will be pink. Predict the genotypic and phenotypic ratios of the offspring for the following:

Rr Rr

Rr Rr

Genotypic Ratio:

100% Rr

Phenotypic Ratio:

100% pink flowers

1. Red and white RR x rr

R R

r

r

Page 3: Incomplete Dominance

Example:

In flowers, petal color demonstrates incomplete dominance. Red results when a flower has homozygous dominant alleles for the trait. White results when a flower has homozygous recessive alleles for the trait. A flower that is heterozygous for this trait will be pink. Predict the genotypic and phenotypic ratios of the offspring for the following:

RR RR

Rr Rr

Genotypic Ratio:

50% RR 50% Rr

Phenotypic Ratio:

50% Red flowers, 50% Pink flowers

2. Red and pink RR x Rr

R R

R

r

Page 4: Incomplete Dominance

Rr Rr

rr rr

Genotypic Ratio:

50% Rr 50% rr

Phenotypic Ratio:

50% Pink flowers 50% White flowers

Genotypic Ratio:

25% RR 50% Rr 25% rr

Phenotypic Ratio:

25% Red flowers 50% Pink flowers 25% White flowers

RR Rr

Rr rr

White and Pink rr x Rr

r r

R

r

Pink and Pink Rr x Rr

R r

R

r

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Codominance

Codominance: condition in which both alleles of a gene are expressed in heterozygous offspring.

Page 6: Incomplete Dominance

Example 1:

In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted.

1. Black cow and White cow BB x WW

BW BW

BW BW

B B

W

W

Genotypic Ratio:

100% BW

Phenotypic Ratio:

100% Spotted cow

Page 7: Incomplete Dominance

Example 1:

In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted.

2. Black cow and Spotted cow BB x BW

BB BB

BW BW

B B

B

W

Genotypic Ratio:

50% BB 50% BW

Phenotypic Ratio:

50% Black cow 50% Spotted cow

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Example 1:

In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted.

3. Both Spotted cows BW x BW

BB BW

BW WW

B W

B

W

Genotypic Ratio:

25 % BB 50% BW 25% WW

Phenotypic Ratio:

25% Black cow 50% Spotted cow 25% White cow

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Example 2:In blood typing, the gene for type A and the gene for type B are codominant. The gene for type O is recessive.

Blood Type (phenotype) Genotype

A AA or AO

B BB or BO

AB AB

O OO

Page 10: Incomplete Dominance

Determine the possible blood types of the offspring when:

1. Mother is type O, Father is type A (homozygous)

AO AO

AO AO

O O

A

A

Genotypic Ratio:

100% AO

Phenotypic Ratio:

100% Type A Blood

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Determine the possible blood types of the offspring when:

AA AB

AO BO

A B

A

O

Genotypic Ratio:

25 % AA 25% AO 25% AB 25% BO

Phenotypic Ratio:

50% Type A Blood 25% Type AB Blood 25% Type B Blood

2. Mother is type AB, Father is Type A (heterozygous)

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Determine the possible blood types of the offspring when:

AB BO

AO OO

A O

B

O

Genotypic Ratio:

25 % OO 25% AO 25% AB 25% BO

Phenotypic Ratio:

25% Type O Blood 25% Type A Blood 25% Type AB Blood 25% Type B Blood

3. Mother is type A (heterozygous), Father is type B (heterozygous)

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Determine the possible blood types of the offspring when:

AB AB

AB AB

B B

A

A

Genotypic Ratio:

100% AB

Phenotypic Ratio:

100% Type AB Blood

4. Mother is type B (homozygous), Father is type A (homozygous)