Lecture 10- Mutations

Question 1

missense mutation

Answer 1

• When one amino acid is changed to another

- An example of a point mutation

Question 2

nonsense mutation

Answer 2

• When an amino acid is changed to a stop codon

- An example of a point mutation

Question 3

silent mutation

Answer 3

• When a nucleotide change doesn’t result in a change in amino acid
• Shouldn’t affect the protein

Question 4

positive selection

Answer 4

-Areas in the genome that are conserved between species and never change

Question 5

null mutation

Answer 5

• a mutation in which there is COMPLETE loss of function
• No functional protein product is made, as the mutation either causes only non-functional proteins to be produced, or the protein doesn’t get made at all
• can be caused by complete deletion of a gene, an early pre-mature stop, or a critical point-mutation
• most loss of function mutations (not just null mutations) are recessive

Question 6

gain of function

Answer 6

• a type of mutation that can come about when too much functional protein is made, or a new protein function is acquired
• this can happen by a deletion of a negative regulatory domain that prevents that protein from being expressed, or being expressed over a certain level
• most gain of function mutations are dominant

Question 7

dominant negative mutation

Answer 7

• a mutation that causes loss of function but is NOT recessive
• it can interfere with the wild type product in a heterozygote

Question 8

haploinsufficient mutation

Answer 8

• when one copy of the wild-type isn’t enough, so the organism still looks mutant
• occurs when there is loss of function in a gene that is very sensitive to dosage
• Having one copy of the wild-type allele is not sufficient to produce the wild-type phenotype b/c this single functional copy of the gene does not produce enough product to display the wild-type’s phenotypic characteristics