4.3: Genetic diversity - mutation

Question 1

what is the advantage of mutations

Answer 1

gives rise to genetic variation, allowing populations to evolve via natural selection

Question 2

What are the 2 types of mutation

Answer 2

Gene/Point mutation, Chromosome mutation

Question 3

when does gene/point mutation happen and what happens

Answer 3

during DNA replication - change in DNA base sequence leads to a change in amino acid sequence which changes the primary structure and so a change in the tertiary structure and therefore a change in function

Question 4

when does chromosome mutation happen and what happens

Answer 4

During meiosis - change in number of chromosomes

Question 5

List the 6 types of gene/point mutations

Answer 5

substitution
insertion
deletion
duplication
inversion
translocation

Question 6

Describe how substitution gene mutation occurs and what follow on effect this has

Answer 6

a single base is copied incorrectly during DNA replication, 1 amino acid maximum could be altered or zero as DNA code is degenerate

Question 7

Describe how insertion gene mutation occurs and what follow on effect this has

Answer 7

A base is added, this results in a frameshift - every codon downstream of the mutation will change, potentially every amino acid downstream of the mutation will be altered

Question 8

Describe how deletion gene mutation occurs and what follow on effect this has

Answer 8

A base is deleted, this results in a frameshift - every codon downstream of the mutation will change, potentially every amino acid downstream of the mutation will be altered

Question 9

Describe how duplication gene mutation occurs and what follow on effect this has

Answer 9

A base is duplicated, this results in a frameshift - every codon downstream of the mutation will change, potentially every amino acid downstream of the mutation will be altered

Question 10

Describe how inversion gene mutation occurs

Answer 10

A group of bases become separated from the DNA, but rejoin in reverse order

Question 11

Describe how translocation gene mutation occurs

Answer 11

A group of bases become separated from the DNA sequence in one chromosome and are inserted into the DNA sequence in a different chromosome

Question 12

During which stage of the cell cycle are gene mutations most likely to occur

Answer 12

Interphase - DNA replication

Question 13

how many homologous pairs do human males have and human females have, and if there is a difference then why?

Answer 13

males = 22
females = 23
males have XY sex chromosomes - not homologous

Question 14

When do chromosome mutations occur

Answer 14

during meiosis anaphase 1/2

Question 15

what are the two types of chromosome mutations

Answer 15

polysomy and polyploidy

Question 16

what is polysomy chromosome mutation and what is this called

Answer 16

one homologous pair fails to separate - non-disjunction

Question 17

what is polyploidy chromosome mutation

Answer 17

all homologous pairs fail to separate

Question 18

What are the resultant number of chromosomes in the 4 daughter cells produced when nondisjunction occurs during meiosis 1

Answer 18

n+1
n+1
n-1
n-1

Question 19

What are the resultant number of chromosomes in the 4 daughter cells produced when nondisjunction occurs during meiosis 2

Answer 19

n+1
n-1
n
n

Question 20

What happens when nondisjunction of chromosome 21 occurs during meiosis

Answer 20

results in a daughter cell having n+1 chromosomes, when it fertilises with a sperm cell containing n for chromosome 21, produces a gamete with 2n+1 for chromosome 21 - this is called Trisomy 21, an extra chromosome for cc 21, this is more widely known as Down’s syndrome

Question 21

are females or males more likely to have nondisjunction occurring and why

Answer 21

females because female gametes start mitosis in the mother’s womb, and then continue at the point of fertilisation

Question 22

What are mutagens

Answer 22

environmental factors that can cause mutations

Question 23

what are the 3 categories of mutagens and give at least 1 example for each

Answer 23

physical - ionising radiation alpha and beta particles, UV/X rays
biological - viruses
chemical - benzopyrene in tobacco smoke