Muller's morphs

Question 1

How are mutations classified in Muller’s morphs?

Answer 1

Based on the effect on gene product function or activity

Question 2

What is a compound heterozygote?

Answer 2

A individual who has two different mutant alleles of a gene

Question 3

What is the Df allele?

Answer 3

Deficient. The gene is deleted

Question 4

What are the 5 Muller’s morphs?

Answer 4

Amorph, hypomorph, hypermorph, antimorph, and neomorph

Question 5

How much gene product activity is seen in an amorph (compared to WT) when:

a) WT/m
b) m/m
c) m/Df

Answer 5

a) Same as the WT if the null allele is recessive. No function if it is dominant
b) No function
c) No function

Question 6

How much gene product activity is seen in a hypomorph (compared to WT) when:

a) WT/m
b) m/m
c) m/Df

Answer 6

a) Same as WT if recessive, less than WT if dominant
b) Less than WT
c) Way less than WT, but still has a bit of function

Question 7

How much gene product activity is seen in a hypermorph (compared to WT) when:

a) WT/m
b) m/m
c) m/Df

Answer 7

a) More than WT
b) A lot more than WT
c) less than with 2 copies of the mutant allele, might be close to the WT phenotype

Question 8

What is a amorphic allele?

Answer 8

An allele that encodes a gene product with no function

Question 9

Are amorphic mutations a gain of function or a loss of function?

Answer 9

Loss of function

Question 10

Are amorphic mutations dominant or recessive?

Answer 10

Usually recessive, but sometimes dominant

Question 11

What is a hypomorphic allele?

Answer 11

An allele whose gene product still has some function, but less function than the WT gene product

Question 12

Are hypomorphic mutations a gain of function or a loss of function?

Answer 12

Loss of function

Question 13

Are hypomorphic mutations dominant or recessive?

Answer 13

Usually recessive, but sometimes dominant

Question 14

How can we tell an amorph and a hypomorph apart?

Answer 14

Homozygous mutant and deficient will have the same phenotype if it is an amorph. They will be different if it’s a hypomorph, which the deficient being more severe

Question 15

What happens to the phenotype if more copies of an amophic allele are added?

Answer 15

Nothing. The alleles have no function

Question 16

What happens to the phenotype if more copies of a hypomorphic allele are added?

Answer 16

The severity of the phenotype is reduced. Can get back to WT with enough copies

Question 17

What is an allelic sequence?

Answer 17

Null alleles and hypomorphic alleles of a gene are arranged from the most to least severe phenotypes

Question 18

What types of mutations could result in a hypomorphic allele?

Answer 18

Mutations in the 5’ UTR that reduce ribosome binding, missense mutations

Question 19

What is a hypermorphic allele?

Answer 19

The mutation either enhances gene product function or makes more copies be produced

Question 20

Are hypermorphs a gain of function or a loss of function?

Answer 20

Gain of function

Question 21

Are hypermorphs dominant or recessive?

Answer 21

Dominant

Question 22

Why can a hypermorphic mutation be lethal in the homozygous state?

Answer 22

The excess of the gene product will poison the cell and it results in the death of the embryo

Question 23

What is the defining feature of a hypermorphic allele?

Answer 23

The deficient mutant has a less severe phenotype than homozygous mutant

Question 24

What are some mutations could result in a hypermorphic allele?

Answer 24

Promotor or enhancer mutations that result in better RNA polymerase binding, which results in more transcription

Question 25

What is an antimorph?

Answer 25

The mutant gene product antagonizes the function of the WT gene product

Question 26

What types of genes could possibly have an antimorphic allele?

Answer 26

Gene products that form a complex and are only functionally active in the complex

Question 27

Are antimorphs a gain of function or a loss of function?

Answer 27

Loss of function

Question 28

Are antimorphs dominant or recessive?

Answer 28

Dominant

Question 29

What is pseudo-reversion?

Answer 29

The introduction of a null mutation into an antimorphic allele, which knocks it out so it stops antagonizing the WT product. Either restores the WT phenotype or it becomes a hypomorph

Question 30

What happens to the phenotype caused by an antimorph if we add more WT alleles?

Answer 30

The severity of the phenotype is reduced, because the gene products of the WT alleles swamp out the mutant ones

Question 31

What is a neomorph?

Answer 31

The gene product has a novel function or activity

Question 32

What sort of events often result in a neomorphic phenotype?

Answer 32

Ectopic expression - the gene product is doing its correct function at the wrong place or time

Question 33

Are neomorphic mutations gain of function or loss of function

Answer 33

Gain of function

Question 34

Are neomorphic mutations dominant or recessive?

Answer 34

Dominant

Question 35

What happens to the phenotype of a neomorphic allele if we add more copies of the WT allele?

Answer 35

No change. We can’t swamp out a neomorph