3.8.1 mutations

Question 1

what is a gene mutation?

Answer 1

a change in the sequence of the base pairs in a DNA molecule, which may result in an altered polypeptide.

Question 2

when does a gene mutation occur?

Answer 2

during DNA replication.

Question 3

what can increase the rate of mutation?

Answer 3

MUTAGENIC AGENTS
- xray.
- radiation.
- chemicals.
- viruses.

Question 4

what is a substitute gene mutation?

Answer 4

a change of a single base (or more) for a different base.

Question 5

what type of mutation is substitution?

Answer 5

a point mutation.

Question 6

what effect does a substitution mutation have?

Answer 6

• may have no effect due to degenerate genetic code = so same amino acid.
• change the amino acid, so it would change the tertiary structure unless the chemical properties are the same.
• introduce a stop codon/triplet and shorten the polypeptide chain.

Question 7

what is a deletion mutation?

Answer 7

when one or more bases are removed.

Question 8

what does a deletion mutation cause?

Answer 8

FRAMESHIFT so all base triplets after the mutation are changed, which causes a significant change in tertiary structure. this is because it changes the number of nucleotides in the sequence so it’s not divisible by 3 and due to translation reading in triplets = the protein made is significantly different.

Question 9

what is an addition mutation?

Answer 9

when one or more bases are added.

Question 10

what does an addition mutation cause?

Answer 10

FRAMESHIFT so all base triplets after the mutation are changed, which causes a significant change in tertiary structure. this is because it changes the number of nucleotides in the sequence so it’s not divisible by 3 and due to translation reading in triplets = the protein made is significantly different.

Question 11

what is an inversion mutation?

Answer 11

when DNA of a single gene is cut in two places and cut proportion is inverted 180° and then rejoined to the same place within the gene.

Question 12

what effect does an inversion mutation have?

Answer 12

• results in a large section of DNA which is ‘backwards’ and therefore multiple amino acids are affected.
• changes tertiary structure of the protein.
• result in a non function protein.

Question 13

what is a silent mutation?

Answer 13

no change to amino acid.

Question 14

what is a nonsense mutation?

Answer 14

produces a STOP codon.

Question 15

what is a missense mutation?

Answer 15

a change to a single amino acid.

Question 16

what is an addition mutation also called?

Answer 16

an insertion mutation.

Question 17

when does an inversion mutation usually occur?

Answer 17

during crossing over in meiosis.

Question 18

what does ‘duplication of a gene’ mean?

Answer 18

a whole gene or section of a gene is duplicated so that two copes of the gene/section appear on the same chromosome.

Question 19

what affect does a duplication of a gene have?

Answer 19

• original version of a gene remains intact and therefore mutation is not harmful.
• the second copy can undergo mutation.

Question 20

what is translocation of a gene section?

Answer 20

a gene is cut in two places and this cut section of the gene attaches to a separate gene.

Question 21

what is the affect of translation of a gene section?

Answer 21

gene that was cut is now non-functional due to having a section missing.

Question 22

what happens if a section of a proton-oncogene is translocated onto a gene controlling cell division?

Answer 22

boosts expression and leads to tumours.

Question 23

what happens if a section of a tumour-suppressor gene is translocated?

Answer 23

a faulty tumour-suppressor gene is produced, which could lead to cell continuing to replicate when it contains faulty DNA.