7.2: types of mutations

Question 1

how to differentiate mutations

Answer 1

1. origin of mutation
2. amount of genetic material changed
3. effect of mutation on DNA
4. effect of mutation on phenotype
5. heritability of mutation

Question 2

origin/cause of mutation

Answer 2

spontaneous vs induced:
- spontaneous: occurs due to an error in a natural process such as DNA replication
- induced: occurs as a result of an environmental agent

Question 3

amount of genetic material changed

Answer 3

point vs frameshift
- point: changes to a single base pair
- frameshift: affects single gene/sequence of genes, can be due to point or chromosomal mutation

Question 4

effect of mutation on DNA

Answer 4

can be substitution, insertion, or deletion of nucleotide bases
- may result in change in one amino acid

Question 5

effect of mutation on phenotype

Answer 5

silent vs variation
- silent: no change in phenotype
- variation: is change in phenotype, can be harmful, neutral, or beneficial

Question 6

heritability of mutation

Answer 6

determines whether or not it will be passed down

Question 7

point mutation

Answer 7

single nucleotide variation
- can cause significant change if occurring within exon, or an intron which affects gene expression

Question 8

base substitution

Answer 8

occurs when one base is replaced by a different base
- may result in different amino acid, which changes function of protein
- if resulting in phenotypic effect, called missense mutation

Question 9

frameshift mutation

Answer 9

occurs when the ‘reading frame’ shifts, creating a whole sequence of incorrect amino acids to produce a non-functional protein
- can be from insertions and deletions
- can be caused by point/chromosomal mutations

Question 10

nonsense mutations

Answer 10

changes an amino acid to a stop codon, cuts protein short
- results in non-functional protein, major phenotypic effect

Question 11

missense mnutations

Answer 11

results in amino acid change
- resulting change in phenotype determined whether or not replacement amino acid is same as the original

Question 12

silent mutations

Answer 12

does not result in change in amino acid
- due to redundancy of genetic code the change is in

Question 13

neutral mutations

Answer 13

amino acid is same type as original
- nothing really changes, same amino acid = same protein structure

Question 14

chromosomal mutation

Answer 14

overall structure changed, or entire number of chromosomes in cell changed

Question 15

four types of mutations that alter structure

Answer 15

deletions, insertions, inversions, translocations

Question 16

chromosomal deletion

Answer 16

section is removed, not replaced
- reduces number of genes in chromosome
- usually result of high exposure to high heat, viruses, or radiation

Question 17

chromosomal insertion/suplication

Answer 17

portion is duplicated, inserted
- increases number of genes on chromosome
- effect and whether it affects phenotype depends on size, location, number of repeats
- copy number variations: when repeat copies is above a certain threshold, results in diseases like huntington’s chorea or fragile X syndrome

Question 18

chromosomal inversion

Answer 18

DNA removed, flipped 180, reinserted
- bases in reverse order
- can cause disease like haemophilia A, which is X-linked

Question 19

chromosomal translocation

Answer 19

section moved from one chromosome to a non-homologous one
- may lead to gene fusion when translocated region joins two separate genes not originally joint

Question 20

aneuploidy

Answer 20

changes in chromosome number