Chapter 2

Question 1

Dominant Epistasis

Answer 1

Epistasis can be caused by a dominant allele
The dominant allele of one gene hides the effects of another gene
The dominant allele of one gene hides the expression of all alleles of another gene
12:3:1 ratio
i.e. squash, Chickens (13:3)
B is epistatic to any A_ genotype (dominant epistasis)
A allele produces color Only in the absence of B; all other combinations are white

Question 2

Redundant Genes

Answer 2

2 genes control leaf Size- They do the same thing
The existance of multiple genes in the genome of an organism that perform the same function
Two or more genes are performing the same function and that inactivation of one of the genes has little or no effect on phenotype
15:1 ratio
i.e. corn

Question 3

Epistasis

Answer 3

An interaction between alleles of different genes, not between alleles of the same gene

Question 4

Genetic Heterogeneity

Answer 4

Heterogeneous traits arise from mutations in any of a set of genes producing a single phenotype
i.e. deafness in humans
Whether A deaf man and a deaf woman Carry recessive Mutations in the Same gene or different ones can be determined if they have Children together. If they have only Children Who can hear, the parents most likely carry mutations at two different genes, and the children carry one normal, wild -type allele for both of those genes. If all their children are deaf, it’s likely both parents,are homozygous for a recessive mutation in the same gene, and all Children are homozygous for the same mutation
Complementation can be used to detect if two individuals carry the same recessive mutation

Question 5

Determining Genetic Basis Of Disease

Answer 5

Breeding studies
examining human pedigrees figure out genetic basis of OCA (Albinism) in humans

Question 6

Penetrance

Answer 6

A measure of the number of individuals of a given genotype who show the expected phenotype (complete, incomplete)

Question 7

Expressivity

Answer 7

The degree or intensity with which a genotype is expressed (variable, unvarying)
Can be affected by modifier genes or the environment

Question 8

Retinoblastoma

Answer 8

75% of carriers develop retinoblastoma in one or both eyes are affected; dominant allele

Question 9

Environmental Effects on Phenotype

Answer 9

Siamese cats - Temperature sensitive allele- siamise allele
Drosophila melanogaster- Conditional lethal allele - shibire allele; viable in permissive range; lethal in restrictive range

Question 10

Continuous Traits in humans

Answer 10

Range of phenotypes due to interaction of several genes with the environment
i.e. height, weight, skin color
Mendelian but with a large number of genes that contribute to the phenotype