Co-dominance in Genetics

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Questions and Answers

What distinguishes co-dominance from complete dominance in genetic expression?

Both alleles express themselves equally. (correct)
One allele is completely dominant over the other.
Only one phenotype is observed in the offspring.
Alleles do not interact at all.

Which of the following genotypes results in a roan phenotype in cattle?

RW (correct)
WW
RR
RR or WW

What is the phenotypic ratio observed in the F2 generation of co-dominant cattle offspring?

1:2:1 (correct)
3:1:1
2:1:1
1:1:1

In co-dominance, how would the offspring inherit their traits if one parent was RR and the other was WW?

<p>All offspring would display a roan phenotype. (D)</p> Signup and view all the answers

Which term best describes the alleles R and W in the context of co-dominance?

<p>Alleles that are both expressed in a heterozygous form. (B)</p> Signup and view all the answers

Flashcards

Co-dominance

Both alleles of a pair are fully expressed, resulting in a phenotype showing both traits equally.

Roan Coat Color in Cattle

A heterozygous individual carrying both alleles for red and white coat color will express both colors equally, resulting in a roan coat.

Phenotypic Ratio in Co-dominance

The F2 generation of a co-dominant cross will have a phenotypic ratio of 1:2:1, meaning one red, two roan, and one white offspring.

Difference between Co-dominance and Complete Dominance

Unlike complete dominance, where one allele masks the other, both alleles in co-dominance are actively expressed.

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Genotype vs Phenotype in Co-dominance

The genotypes in a co-dominant cross represent the combination of alleles in an individual, while phenotypes represent the visible trait.

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Study Notes

Co-dominance

Co-dominance is a type of inheritance where both alleles of a gene pair are fully expressed in the heterozygote, resulting in a phenotype that is neither dominant nor recessive.
In co-dominance, both alleles are expressed equally in the hybrid, unlike dominance where one is expressed over the other.
An example of co-dominance is seen in the different coat colours such as: red, white, and roan.
In this example, the alleles for red (R) and white (W) are co-dominant.
The possible genotypes are RR (red), RW (roan), and WW (white)
A cross between a red cow (RR) and a white cow (WW) produces roan offspring (RW).
The phenotypic ratio (observed traits) in the F2 generation when crossing two roan cows (RW x RW) is 1 red:2 roan:1 white
The genotypic ratio (genetic makeup) in the F2 generation when crossing two roan cows (RW x RW) is 1RR:2RW:1WW.

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Description

This quiz explores the concept of co-dominance in genetics, where both alleles are fully expressed in a heterozygote. You'll learn about examples, genotype and phenotype ratios, and the inheritance patterns of co-dominant traits, such as coat colors in cattle. Test your understanding of this important genetic principle.