Lectures 3-5

Question 1

How many alleles exist in a diploid cell for one particular gene?

Answer 1

2

Question 2

What is haplosufficiency?

Answer 2

Wild type is dominant over loss of function allele, less protein, but is often sufficient enough to achieve wild type phenotype

Question 3

What is a gain of function mutation?

Answer 3

Mutant allele produces a protein that has increased detrimental function

Question 4

Haploinsufficient?

Answer 4

Half as much protein is synthesized, and this is now sufficient for normal phenotype

Question 5

What is a recessive lethal allele?

Answer 5

Essential genes, when mutated, lead to lethal phenotype, homozygous is lethal

Question 6

What is a dominant lethal allele?

Answer 6

Can be expressed in both homozygous and heterozygous

Question 7

How do recessive mutations impact the polypeptide?

Answer 7

Diminish polypeptide acitivity

Question 8

What is penetrance?

Answer 8

Proportion of individual organisms having a particular genotype that express the expected phenotype - variation in the population

Question 9

What is expressivity?

Answer 9

The degree to which a phenotype is expressed - variation in the individual

Question 10

What causes penetrance and expressivity?

Answer 10

Due to effects of environmental factors and other genes

Question 11

What are some environmental factors that affect phenotypic expression?

Answer 11

Age, sex, temperature, chemicals

Question 12

What is a phenocopy?

Answer 12

Change in phenotype arising from environmental factors that mimic the effects of a mutation in a gene

Question 13

What is the law of independent assortment?

Answer 13

Inheritance of one trait will not affect the inheritance pattern of another trait

Question 14

What is genetic interaction?

Answer 14

Different combinations of alleles from two+ genes can result in different phenotypes

Question 15

What is complementation?

Answer 15

Occurs when two strains with different homozygous recessive mutations that produce the same phenotype produce offspring with wild type phenotype when crossed. Only occurs if mutations are in different genes

Question 16

What is a heterogeneous trait?

Answer 16

Mutation in any one of a number of genes can give rise to the same phenotype?

Question 17

What is epistasis?

Answer 17

Masking of the expression of one gene by another

Question 18

Recessive epistasis?

Answer 18

Recessives one one gene pair mask expression from another gene

Question 19

Dominant epistasis?

Answer 19

One dominant allele at one gene masks the expression from the other gene

Question 20

F2 ratios?

Answer 20

3:1 - complete dominance
1:2:1 - incomp. Dominance or co-dom
2:1 - recessive lethal
9:3:3:1 - complete dominance
9:3:4 - recessive epistasis
9:7 - complementation
12:3:1 - dominant epistasis

Question 21

What is pleiotropy?

Answer 21

Single gene can be responsible for number of distinct and seemingly unrelated phenotypic effects

Question 22

What is inbreeding depression?

Answer 22

Inbred lines of species are less vigorous than hybrid

Question 23

Hybrid vigour (heterosis)

Answer 23

When two different inbred lines are crossed, hybrids are vigorous

Question 24

What is the hardy-Weinberg equilibrium?

Answer 24

p^2 + 2pq + q^2 = 1

Question 25

What is X-inactivation?

Answer 25

Random inactivation of one x from females, if a cell contains more than one X chromosome, all but one are inactive, e.g. Barr bodies XXX has two Barr bodies