Basic Principles and extensions

Question 1

Null allele

Answer 1

Nonfunctional

Question 2

Hypomorphic allele

Answer 2

partial function
Enzyme or other protein is no longer being produced, produced at a lower rate
or is nonfunctional

Question 3

Gain of function mutation

Answer 3

Increased detrimental function

Question 4

Haplosufficiency

Answer 4

Half as much protein is synthesized yet is often enough to achieve the wildtype phenotype

Question 5

Haploinsufficiency

Answer 5

Protein synthesized is not enough for normal phenotype

Question 6

Recessive lethal alleles

Answer 6

Essential genes that when mutated can lead to a lethal phenotype
2 copies needed for it to be lethal

Question 7

Huntingtons

Answer 7

Dominant lethal alleles, degenerative with late onset of symptoms

Question 8

Recessive amorphic

Answer 8

Loss of function allele that does not produce a functional polypeptide
Severe mutant phenotype

Question 9

Recessive hypomorphic

Answer 9

Loss of function allele produces a partially functional polypeptide
mild mutant phenotype

Question 10

Dominant negative

Answer 10

Allele produces polypeptide that interferes with wild type

Severe mutant phenotype

Question 11

Penetrance

Answer 11

Proportion of individual organisms having a particular genotype that expresses the phenotype, variation in the population
Polydactyly is an example of variable penetrance8

Question 12

Expressivity

Answer 12

Degree to which a phenotype is expressed, variation in the indivual
Split hand/foot syndrome are rare autosomal dominant disorders that shows variable expressivity

Question 13

Norm of reaction

Answer 13

Range of phenotypes expressed by a single genotype under different environmental conditions

Question 14

Temperature sensitive allele

Answer 14

Siamese allele in cats

Question 15

Phenocopy

Answer 15

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

Question 16

Complementation

Answer 16

Occurs when 2 strains of an organisms with different homozygous recessive mutations that produce same phenotype produce offspring of the wildtype phenotype when crossed
Only occur when mutations are in different genes

Question 17

Genetic epistasis

Answer 17

Masking of the expression of one gene by another. No new phenotypes are produced

Question 18

F2 phenotypic ration 9:3:4

Answer 18

Recessive epistasis

Question 19

F2 phenotypic ration 12:3:1

Answer 19

dominant epistasis

Question 20

f2 phenotypic ration 9:7

Answer 20

Complementation

Question 21

Pleiotropy

Answer 21

Single gene responsible for multiple distinct and seemingly unrelated phenotypic effects
sickle cell disease and cystic fibrosis

Question 22

Inbreeding

Answer 22

Reveals recessive alleles that have been masked before

Question 23

Inbreeding depression

Answer 23

Occurs in plants

may not be able to adapt to environmental change and more susceptible to wide spread disease (monoculture)

Question 24

Hetersosis

Answer 24

When 2 different inbred lines are crossed they form heterozygotes for several genes and express hybrid vigour

Question 25

Hardy-Weinberg principle

Answer 25

Prediction of genotypes through measure of allele frequencies
p^2+2pq+q^2 =1
f(A)=p f(a)=q f(AA)=p^2 f(Aa)=2pq f(aa)=q^2
Holds true but only in the absence of evolutionary infulences

Question 26

Dosage compensation

Answer 26

Way of equalizing gene expression in the face of different gene dosage
X and Y chromosomes pair during meiosis even though they are not homologous

Question 27

Chromosomal sex-determination

Answer 27

In insects, sex determined by raito of x chromosomes Males have a single x females have 2
In mammals, sex has to do with presence of Y chromosome

Question 28

X-inactivation

Answer 28

If a cell contains 2 or more x chromosomes, all but one of them are inactive