Causes of mutations

Question 1

what mutagens/agents cause mutations

Answer 1

• physical mutagens
• chemical mutagens
• biological agents

Question 2

what are physical mutagens

Answer 2

Physical mutagens cause double-strand breaks. Double-strand breaks are a mutation involving breaks in the sugar phosphate back bones of both DNA strands at the same nucleotide pair, resulting in the complete breakage of a chromosome.

Question 3

what are three physical mutagens

Answer 3

1. UV light
2. X rays
3. nuclear radiation

Question 4

describe the effect UV light has

Answer 4

Ultraviolet light can cause distortions in the double helix. Adjacent thymine bases are joined together to create a thymine dimer.

Question 5

describe the effect X-rays and nuclear radiation have

Answer 5

Causes the breaking or severing of DNA strands

Question 6

what are chemical mutagens

Answer 6

Chemical mutagens involve the substitution of bases with other chemicals. This can cause replication errors or prevent transcription.

Question 7

what are four chemical mutagens

Answer 7

1. mustard gas
2. aminopurine
3. colchicine
4. nitric acid

Question 8

describe the effect of mustard gas

Answer 8

affects the base guanine causing a substitution mutation

Question 9

describe the effect of aminopurine

Answer 9

causes nucleotide substitution

Question 10

describe the effect of colchicine

Answer 10

prevents spindle fibre formation in mitosis and so doubles chromosomes number

Question 11

describe the effect of nitric acid

Answer 11

causes adenine in DNA to be deaminted so it behaved like guanine

Question 12

what are biological agents

Answer 12

Biological agents can arise because of the action of invasive pathogens including bacteria and viruses. DNA can become permanently integrated into the cell’s DNA.

Question 13

what is a dimer

Answer 13

A dimer is two bases joined together