Genetic information - MUTATIONS AND THEIR EFFECTS

Question 1

What is a mutation?

Answer 1

Any change to the quantity or base sequence of DNA

Question 2

What is a gene mutation?

Answer 2

Any change to one or more nucleotide bases, or a change in the sequence of bases in DNA

Question 3

What effect will a change in one or more of the bases in the DNA triplet have on the structure of a protein?

Answer 3

• Change in the sequence of amino acids
• Primary structure changes
• Hence all other structures of protein will change

Question 4

What are the 7 different types of mutations?

Answer 4

• Substitution
• Deletion
• Addition
• Duplication
• Inversion
• Translocation
• Chromosome mutations

Question 5

What is a substitution mutation?

Answer 5

When a nucleotide is replaced by another nucleotide that has a different base

Question 6

What is the effect of a substitution mutation?

Answer 6

• The original amino acid may be replaced, changing the shape of the protein, and limiting the function (especially true of enzymes)
• Original amino acid may be replaced, but there is no effect on formation of bonds and protein will function normally
• Mutation may even lead to the same amino acid being coded for (DNA is degenerative)

Question 7

What are silent mutations?

Answer 7

Mutations that occur but do not change the amino acid produced

Question 8

What is a deletion mutation?

Answer 8

When a base is removed, re-ordering how the bases are read from the point of deletion (FRAMESHIFT)

Question 9

What is the effect of a deletion mutation?

Answer 9

• Likely to result in an entirely different polypeptide sequence
• Protein is unlikely to function

Question 10

What is an addition mutation?

Answer 10

An extra base is inserted into the sequence

Question 11

What is the effect of an addition mutation?

Answer 11

Frameshift to the right

Question 12

What is a duplication mutation?

Answer 12

One or more bases are repeated

Question 13

What is the effect of a duplication mutation?

Answer 13

Frameshift to the right

Question 14

What is an inversion mutation?

Answer 14

Group pf bases become separated from the DNA sequence and re-join at the same position but back to front

Question 15

What is the effect of an inversion mutation?

Answer 15

Amino acid sequence is changed

Question 16

What is a translocation mutation?

Answer 16

A group of bases becomes separated from the DNA sequence on one chromosome and is inserted onto another

Question 17

What is the effect of a translocation mutation?

Answer 17

• Significant errors and abnormal phenotypes
• For example, certain types of cancer and infertility

Question 18

What are chromosome mutations?

Answer 18

• Changes to the structure/number of whole chromosomes
• Due to failure to separate during meiosis
• A gamete may have one more or one fewer chromosomes

Question 19

What are the causes of mutations?

Answer 19

• Mutations arise spontaneously during DNA replication
• However, mutation rate can be increased with exposure to mutagenic agents

Question 20

Give some examples of mutagenic agents

Answer 20

• High energy ionising radiation: Alpha and beta particles disrupt the structure of DNA
• Certain chemicals: Alter the structure of DNA or interfere with transcription