Lecture 11

Question 1

Incomplete dominane

Answer 1

heterozygotes show an intermediate phenotype – genotypic=phenotypic

Question 2

Co-dominance

Answer 2

heterozygotes show phenotype of both alleles

Question 3

Pleiotropy

Answer 3

one gene contributes to more than one trait

Question 4

Lethal alleles

Answer 4

normally when homozygous, can cause skewed phenotypic ratios, indicates an essential gene

Question 5

Sickle cell anaemia

Answer 5

an example of the complications of dominance and pleiotropy, physiological level incomplete dominance, biochemical level – codominance

Question 6

Describe the genes in coat colour in mammals

Answer 6

• A gene- distribution of pigment in hair
• B gene- colour of pigment in hair
• C gene- permits colour expression
• D gene- intensity of pigment specified by other genes
• S gene- controls distribution of pigment

Question 7

epistasis

Answer 7

gene interation in which the effects of an allele at one gene hide the effects of alleles at another gene

Question 8

Complementation tests

Answer 8

determine if a phenotype in the same or separate genes

Question 9

Penetrance

Answer 9

measures the percent of individuals with a given genotype who exhibit the phenotype associated with the genotype – a phenotype is not always expressed even though they carry the mutant allele

Question 10

Expressivity

Answer 10

measures the extent to which a given genotype is expressed at phenotypic level