Gene interaction

Question 1

What is the difference between the molecular basis of dominance? (ie. Is there dominance or recessive terms)

Answer 1

The dominance of one allele over another is determined by the protein product of that allele: phenotypic
basis
- Overall phenotype is the consequence of the activities of the protein products of the alleles of the gene

Question 2

Define and understand halpoinsufficient gene?

Answer 2

One wild type dose produces insufficient amounts of protein product for a normal phenotype.

Question 3

What are wild type alleles? Are they usually recessive or dominant?

Answer 3

• mutant allele dominant to wild type
• When the mutant allele produces less of an enzyme, and on copy, of a wild-type allele is unable to produce normal function (haploinsufficient)

Question 4

What are the two types of functional effects of mutant alleles?

Answer 4

• Loss of function: significant decrease or complete loss of functional gene product
• Gain of function: gene product acquires a new function or expresses increased wild-type activity

Question 5

incomplete dominance genotypic and phenotypic

Answer 5

heterozygous individuals display intermediate phenotypes between either homozygous type, usually being more similar to one of the homozygous types
- Neither trait is dominant, each dose of wild-type adds more pigment
- Red flower + white flower = pink flower
- 1:2:1

Question 6

codominance genotypic and phenotypic

Answer 6

leads to heterozygotes with a different phenotype than that of either homozygote
- Detectable expression of both alleles in heterozygotes, may exhibit either or both
- ABO blood type
- 1:2:1

Question 7

In mice, the yellow allele is lethal when homozygous and dominant to the agouti allele in heterozygotes. In a cross between two yellow mice, what will the phenotype of the offspring be?

Answer 7

All yellow mice are heterozygous because it is a recessive embryonic lethal, A^yA^y will be lethal

Question 8

Dominant lethal alleles are, in most cases, eliminated from populations. In which case can they persist in a population? Give an example

Answer 8

If they have a late stage of onset
- Ex: Huntington’s disease - autosomal dominant

Question 9

Imagine that you are a Labrador breeder and you have a pair of dogs with known genotype for coat color: your male has the genotype (bbEe) and your female (BBee).
a. What are the colors of your two dogs?
b. Your friend wants to buy a chocolate Labrador and you offer him to sell one of the puppies from a cross between your dogs. Will your dogs be able to produce a
chocolate puppy? What is the name of this type of gene interaction?

Answer 9

a. Male is chocolate, Female is yellow
b. Recessive epistasis (1:1 black and yellow)

Question 10

What is pleiotropy? Give an example.

Answer 10

It is the alteration of multiple distinct traits by a mutation in a single gene.
- Drosophila, juvenile hormone influences numerous attributes of development and reproduction
such as body size, development, sexual maturity, and others
- Sick cell disease, many red blood cells of people with this take on a sickle shape and cause
numerous physical problems and complications -> range of phenotypic consequences
- Deafness in blue eyed white cats
- Apaloosa coat color and night-blindness

Question 11

Complementary Analysis: why is it important and what can it distinguish?

Answer 11

Cis-trans test determines whether two mutations associated with a specific phenotype represent two different forms of the same gene or are variations of two different genes

Question 12

Define and understand haplosufficient

Answer 12

Both +/+ and +/m produce sufficient
amounts of protein product for a normal phenotype.

Question 13

complete penetrance

Answer 13

If a given genotype always produces the same phenotype. The genes for a trait are expressed in all the population who have the gene

Question 14

Penetrance

Answer 14

the percentage of individuals that show
at least some degree of expression of the mutant genotype in a population
- partial penetrance

Question 15

Expressivity

Answer 15

The range (‘degree’) of expression of the mutant phenotype
- Can be the result of genetic background differences and/or
environmental effects

Question 16

incomplete Penetrance

Answer 16

the genetic trait is expressed in only part of the population

Question 17

variable expressivity

Answer 17

individuals who carry the alleles for a trait show a phenotype but to a varying degree of severity or form of expression: the variation in phenotypic expression

Question 18

Epistasis

Answer 18

When an unrelated gene affects the phenotypic expression of another gene
- 9:3:3:1 is the expected ratio of an F2 dihybrid cross with no epistasis

Question 19

Complementary Epistasis

Answer 19

(9:7), when genes work in tandem to produce a single product

Question 20

Duplicate Epistasis

Answer 20

(15:1), Genes encode same product or encode products that have the same effect in a pathway or compensatory pathways
- dominant allele at either locus gives rise to a wild-type phenotype
- Redundant system

Question 21

Dominant epistasis

Answer 21

(12:3:1), The ability of a dominant allele at one locus to override or mask the interacting allele(s) of a second locus

Question 21

Recessive Suppressor

Answer 21

mutant allele (i.e. the suppressor) of one gene reverses the mutant effect at another gene, resulting in wild type or near wild type phenotype
-13:3

Question 22

Recessive epistasis

Answer 22

(9:3:4), Ability of a recessive allele at one locus to override or mask the interacting alleles of a second locus

Question 23

Dominant suppression Epistasis

Answer 23

(13:3), Suppressor dominant gene has no mutant phenotype, only acts as a suppressor to inhibit the effect of another dominant allele