Relating Genotype to Phenotype

Question 1

Give the dominant/recessive interactions between alleles of a gene and what this means in diploids.

Answer 1

Wild type allele = functional protein
Mutant allele = often non-functional or unstable protein
Therefore in diploids:
-many wild types are dominant
-many mutant alleles are recessive

Question 2

Give the definition of codominance.

Answer 2

Heterozygotes show phenotype of both alleles.

Question 3

Describe the interaction of dominant/recessive with multiple alleles.

Answer 3

You establish a dominance hierarchy for a gene.

Eg dominance series A > a^t > a.

Question 4

Give the definition of pleiotropy & an example.

Answer 4

One gene contributes more to one than one trait.

Eg gene involved in cilia and flagella function.

Question 5

Give the effect of lethal alleles & what they indicate.

Answer 5

Cause skewed phenotypic ratios, indicates an essential gene.

Question 6

Give the definition of epistasis.

Answer 6

The effects of one allele at one gene hide the effects of alleles at another gene.

Question 7

Give the purpose of complementation tests.

Answer 7

Determine if a phenotype arises from mutations in the same or separate genes.

Question 8

What does penetrance measure?

Answer 8

% of individuals with a given genotype who exhibit the phenotype associated with the genotype.

Question 9

What does expressivity measure?

Answer 9

The extent to which a given phenotype is expressed at the phenotypic level.