Muller's morphs Flashcards
How are mutations classified in Muller’s morphs?
Based on the effect on gene product function or activity
What is a compound heterozygote?
A individual who has two different mutant alleles of a gene
What is the Df allele?
Deficient. The gene is deleted
What are the 5 Muller’s morphs?
Amorph, hypomorph, hypermorph, antimorph, and neomorph
How much gene product activity is seen in an amorph (compared to WT) when:
a) WT/m
b) m/m
c) m/Df
a) Same as the WT if the null allele is recessive. No function if it is dominant
b) No function
c) No function
How much gene product activity is seen in a hypomorph (compared to WT) when:
a) WT/m
b) m/m
c) m/Df
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
How much gene product activity is seen in a hypermorph (compared to WT) when:
a) WT/m
b) m/m
c) m/Df
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
What is a amorphic allele?
An allele that encodes a gene product with no function
Are amorphic mutations a gain of function or a loss of function?
Loss of function
Are amorphic mutations dominant or recessive?
Usually recessive, but sometimes dominant
What is a hypomorphic allele?
An allele whose gene product still has some function, but less function than the WT gene product
Are hypomorphic mutations a gain of function or a loss of function?
Loss of function
Are hypomorphic mutations dominant or recessive?
Usually recessive, but sometimes dominant
How can we tell an amorph and a hypomorph apart?
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
What happens to the phenotype if more copies of an amophic allele are added?
Nothing. The alleles have no function
What happens to the phenotype if more copies of a hypomorphic allele are added?
The severity of the phenotype is reduced. Can get back to WT with enough copies
What is an allelic sequence?
Null alleles and hypomorphic alleles of a gene are arranged from the most to least severe phenotypes
What types of mutations could result in a hypomorphic allele?
Mutations in the 5’ UTR that reduce ribosome binding, missense mutations
What is a hypermorphic allele?
The mutation either enhances gene product function or makes more copies be produced
Are hypermorphs a gain of function or a loss of function?
Gain of function
Are hypermorphs dominant or recessive?
Dominant
Why can a hypermorphic mutation be lethal in the homozygous state?
The excess of the gene product will poison the cell and it results in the death of the embryo
What is the defining feature of a hypermorphic allele?
The deficient mutant has a less severe phenotype than homozygous mutant
What are some mutations could result in a hypermorphic allele?
Promotor or enhancer mutations that result in better RNA polymerase binding, which results in more transcription
What is an antimorph?
The mutant gene product antagonizes the function of the WT gene product
What types of genes could possibly have an antimorphic allele?
Gene products that form a complex and are only functionally active in the complex
Are antimorphs a gain of function or a loss of function?
Loss of function
Are antimorphs dominant or recessive?
Dominant
What is pseudo-reversion?
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
What happens to the phenotype caused by an antimorph if we add more WT alleles?
The severity of the phenotype is reduced, because the gene products of the WT alleles swamp out the mutant ones
What is a neomorph?
The gene product has a novel function or activity
What sort of events often result in a neomorphic phenotype?
Ectopic expression - the gene product is doing its correct function at the wrong place or time
Are neomorphic mutations gain of function or loss of function
Gain of function
Are neomorphic mutations dominant or recessive?
Dominant
What happens to the phenotype of a neomorphic allele if we add more copies of the WT allele?
No change. We can’t swamp out a neomorph
