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

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

Answer 9

Interphase - DNA replication

Question 10

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

Answer 10

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

Question 11

When do chromosome mutations occur

Answer 11

during meiosis anaphase 1/2

Question 12

what are the two types of chromosome mutations

Answer 12

polysomy and polyploidy

Question 13

what is polysomy chromosome mutation and what is this called

Answer 13

one homologous pair fails to separate - non-disjunction

Question 14

what is polyploidy chromosome mutation

Answer 14

all homologous pairs fail to separate

Question 15

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

Answer 15

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

Question 16

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

Answer 16

n+1
n-1
n
n

Question 17

What happens when nondisjunction of chromosome 21 occurs during meiosis

Answer 17

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 18

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

Answer 18

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

Question 19

What are mutagens

Answer 19

environmental factors that can cause mutations

Question 20

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

Answer 20

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