Topic 3

Question 1

Mutations of haplosuffient genes are _______

Answer 1

recessive

Question 2

Dominant negative (lethal)

Answer 2

homozygous is mutant, sometimes is lethal. Heterozygous is mutant, but not lethal

Question 3

ratio of dominant lethal alleles

Answer 3

2 domiant to 1 recessive

Question 4

allelic series

Answer 4

dominace hierarchy of multiple alleles

Question 5

null allele

Answer 5

non-functional and likely recessive to all other alleles

Question 6

hypomorphic allele

Answer 6

has partial function

Question 7

Incomplete dominance

Answer 7

appearance of 3 phenotype that blends 2 parental ones (no clear dominance)

Question 8

Codominance

Answer 8

More than 1 allele is dominant, causing both parental phenotypes to be displayed

Question 9

penetrance

Answer 9

the proportion of individuals of the same genotype that will either express the determined phenotype or not express it at all

Question 10

What determines penetrance of the phenotype?

Answer 10

modifier genes
environmental factors
allelic variation
complex genetic and environmental interactions

Question 11

expressivity

Answer 11

the degree or intensity with which a genotype is expressed (all display mutation, but there are many degrees of severity

Question 12

pleiotropy

Answer 12

one gene controlling 2 or more apparently unconected phenotypes

Question 13

polygenic inheritance

Answer 13

a phenotype affected by many different genes

Question 14

________ _________are often polygenic and their effect on the phenotype incremental

Answer 14

Qualitative traits

Question 15

How to test if a phenotype is due to expression of a single locus or more?

Answer 15

complementation tests show that if complement does not occur, it indicates alleslism. Complementation indicates non-allelic mutants

Question 16

allelism

Answer 16

one locus involved

Question 17

non-allelic mutants

Answer 17

more than 1 gene is responsible for same phenotype

Question 18

Suppressor mutations

Answer 18

mutation that suppresses other mutations

Question 19

Enhancer mutation

Answer 19

strengthens mutant phenotype

Question 20

Intra-genic interaction (allelic)

Answer 20

dominance, recessiveness, co-dominance, incomplete dominance

Question 21

Allele-environment interaction

Answer 21

penetrance, expressivity

Question 22

Extra-genic interaction

Answer 22

suppresion, enhancement, genetic pathways

Question 23

Additive gene action

Answer 23

alleles of 2 genes generating 4 phenotypes in a single trait (2 loci, 1 trait, 4 phenotypes). Has same phenotypic ratio 9:3:3:1

Question 24

Complementary gene action

Answer 24

only 2 phenotypes. Homozygous recessive for both/either genes produces 1 phenotype, while homozygous dominant for both/either gene produces a different phenotype (9:7 ratio)

Question 25

redundancy (duplicate gene action)

Answer 25

dominant alleles of both genes overpowers each others recessive alleles and produces the same phenotype (15: 1 ratio)s

Question 26

Epistatic

Answer 26

a mutant allele of 1 geneoverrides the phenotypic effect of a mutant allele of another gene when both are present in the same genotype (ex: white eye is expressed over the red eye)

Question 27

hypostatic

Answer 27

suppressed phenotype

Question 28

Dominance vs. epistasis

Answer 28

Dominance - intra-allelic gene interaction (1allele hides the other allele of the same locus)
Epistasis - inter-allelic gene interaction (1 gene hides affect of another gene)

Question 29

recessive epistatis

Answer 29

when the recessive allele of 1 gene masks the effect of either (dom/rec) allele of the second gene (9:3:4)

Question 30

dominant epistasis

Answer 30

when the dominant allele of 1 gene masks the effects of either (dom/rec) allele of the second gene (12:3:1)