8.5 The effects of mutations on gene expression and function

Question 1

What are the 4 types of mutations

Answer 1

Silent mutations, nonsense mutations, missense mutation, frameshift mutation

Question 2

Missense mutations

Answer 2

replace one amino acid with another.

Question 3

What are the two types of missense mutations

Answer 3

conservative and nonconservative

Question 4

Explain coonservative missense mutation

Answer 4

The chemical properties of mutant amino aicd are similar to the original amino acid
eg: Aspartic acid to glutamic acid

Question 5

Explain noncoservative missense mutation

Answer 5

The chemical properties of the mutant amino aicd are different from the original amino acid
eg: aspartic acid (-ve charge) to alanine (neutral)

Question 6

Nonsense mutations

Answer 6

chnage a codon that encodes an amino acid to a stop codon (UAA,UAG,UGA)

Question 7

Frameshift mutations

Answer 7

result from insertions or deletions of nucleotides with the coding region resulting in changes in the reading frame of codons. However no frameshift occurs if multiples of three are inserted or deleted (restores reading frame)

Question 8

Silent mutations

Answer 8

do not alter the amino acid sequence (Degenerate genetic code-most amino acids have >1 codon)

Question 9

Loss-of-function mutant alleles are usually _______ to wild-type

Answer 9

recessive

Question 10

Null (amorphic) mutations

Answer 10

completely block function of a gene product (eg: deletion of an entire gene)

Question 11

Hypomorphic mutations

Answer 11

gene product has weak, but detectable, activity

Question 12

Some loss-of-function alleles can show ____________________

Answer 12

incomplete dominance

Question 13

Incomplete dominance

Answer 13

phenotypes varies continuously with the amount of functional gene product

Question 14

some loss of function alleles are__________ to wildtype

Answer 14

Dominant

Question 15

Haploinsufficiency

Answer 15

Where a single wild-type allele is insufficient to produce enough protein to prevent a mutant phenotype.

Question 16

Give an example of haploinsufficiency

Answer 16

GLI3/GLI3+ = polydactyly

Question 17

Gain of function mutations are usually ____________

Answer 17

dominant

Question 18

Hypermorphic mutations

Answer 18

generate more gene product or the same amount of a more efficient gene product

Question 19

_____________ is caused by a dominant hypermorphic allele of FGFR3. The altered protein is always active

Answer 19

Achondroplasia

Question 20

The FGFR3 gene encodes a transmembrane receptor that _____________

Answer 20

is usually active only when bound to the FGF hormone. The mutation causes the protein to always be active, i.e the “stop bone growth” signal is always on.

Question 21

Neomorphic mutations

Answer 21

Generate gene product with new function or that is expressed at inappropriate time or place

Question 22

_________________(dominant negative) alleles fail to provide wild-type activity AND prevent the normal protein from functioning

Answer 22

Antimorphic

Question 23

In which genes do antimorphic mutations usually occur

Answer 23

in genes that encode multimeric proteins