TOPIC 8 - DNA and the structure of proteins

Question 1

what is a mutation?

Answer 1

alteration in the DNA base sequence. Often arise spontaneously during DNAA replications.

Question 2

what are addition and deletion mutations?

Answer 2

where one or more nucleotides are either inserted or deleted from the DNA sequence

Question 3

what is a substitution mutation?

Answer 3

where one nucleotide (Base) in the DNA sequence is replaced by another.

Question 4

what is a duplication mutation?

Answer 4

where one or more nucleotides (bases) duplicate and repeat

Question 5

what is an inversion mutation?

Answer 5

where a group of nucleotides (bases) become separated from DNA sequence, then rejoin in the reverse order.

Question 6

what is a translocation mutation?

Answer 6

where a group of nucleotides (bases) become separated from the DNA sequence, and are then inserted into the DNA of a different chromosome.

Question 7

which mutations are most likely to have a significant impact and why?

Answer 7

insertion, deletion, duplication and translocation = an entire amino acid sequence produced will be different

Question 8

which mutations are most likely to have a smaller impact and why?

Answer 8

substitution and inversion = only alter a few triplets, amino acid sequence might not be affected due to degenerate nature of the genetic code.

Question 9

Is a mutation resulting in a change to the amino acid sequence alway harmful?

Answer 9

NO - may be neutral if the resulting change in a protein has no effect on the organism.
May be beneficial = basis for evolution and natural selection

Question 10

what is a mutagenic agent?

Answer 10

factors that increase the rate of gene mutation
eg chemical mutagens alcohol and benzene
Ionising radiation = UV and X-ray