19.1 mutations and variation

Question 1

what is a mutation?

Answer 1

change in the sequence of bases in DNA

Question 2

how is protein synthesis affected by a mutation?

Answer 2

the wrong bases and transcribed which means that translation would lead to the wrong amino acids being produced and thus a different primary structure of a protein

so the final 3D structure may change

Question 3

what are the three types of mutation?

Answer 3

substitution
deletion
insertion

Question 4

what is a substitution mutation?

Answer 4

when a nucleotide is substituted for another which leads to a different codon

Question 5

when can a substitution mutation lead to no change?

Answer 5

when the codon replacing the original codon codes for the same amino acid and so the same protein is produced

DEGENERATE NATURE OF GC

Question 6

what is a deletion mutation?

Answer 6

when one or more nucleotides are removed

Question 7

what is an insertion mutation?

Answer 7

when one or more nucleotides are added

Question 8

what does insertion and deletion lead to?

Answer 8

a frameshift mutation

Question 9

what is a frameshift mutation?

Answer 9

by adding or removing a nucleotide, you displace the following codons which, due to the non-overlapping nature of the GC, changes every successive codon

so changes the base sequence

Question 10

what are the 3 effects of a mutation?

Answer 10

no effect
damaging
beneficial

Question 11

no effect

Answer 11

mutation causes no effect on the phenotype of an organism

Question 12

damaging

Answer 12

mutation causes major change to an organism’s phenotype which prevents essential processes

Question 13

beneficial

Answer 13

mutation causes a change to an organism’s phenotype which provides an advantageous characteristic

Question 14

when can a mutation have no effect?

Answer 14

mutation changes a base in a codon but the codon stays the same so the same amino acid is translated

mutation changes a base in a codon and a different amino acid is translated BUT the new amino acid is chemically similar to the original so functions very similarly

Question 15

how do mutations occur?

Answer 15

spontaneously during DNA replication

Question 16

what is a mutagen?

Answer 16

an agent which causes mutations

increases the rate of mutations

Question 17

what is depurination?

Answer 17

the loss of a purine base

Question 18

what is depyrimidination?

Answer 18

the loss of a pyramidine bae

Question 19

what do depurination and depyrimidination cause?

Answer 19

leads to the incorrect base being used through complimentary base pairings

Question 20

what are the effects of free radicals on nucleotide structure?

Answer 20

they disrupt base pairing in DNA replication

Question 21

what is a silent mutation?

Answer 21

mutation which has no effect on the phenotype

Question 22

what is a nonsense mutation?

Answer 22

mutation which causes a stop codon to be synthesised which shortens the protein structure

Question 23

what is a missense mutation?

Answer 23

mutation which causes the wrong amino acid to be synthesised

Question 24

how is lactose-tolerance a beneficial mutation?

Answer 24

allows a mammal to digest lactose

Question 25

what are the mutations a chromosome can undergo?

Answer 25

deletion
duplication
translocation
inversion

Question 26

deletion in a chromosome

Answer 26

section of a chromosome breaks off and is lost in the cell

Question 27

duplication in a chromosome

Answer 27

sections of a chromosome get duplicated

Question 28

translocation in a chromosome

Answer 28

section of a chromosome breaks off an joins a non-homologous chromosome

Question 29

inversion in a chromosome

Answer 29

section of a chromosome is removed, reversed and then reinstated