9.1) Gene mutation

Question 1

What is a mutation?

Answer 1

A mutation is any change to the quantity or the base sequence of the DNA of an organism

Question 2

What is a gene mutation?

Answer 2

A gene mutation is a change in the sequence of the bases in DNA

Question 3

How do mutations arise?

Answer 3

They arise spontaneously during DNA replication

Question 4

What are the two main types of gene mutation?
1.
2.

Answer 4

1. Base substitution
2. Base deletion

Question 5

What is base substitution?

Answer 5

A type of gene mutation where a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base

Question 6

What are the two possible effects of base substitution?

Answer 6

The new triplet codes for the same amino acid as before and there is no effect

The new triplet codes for a different amino acid so the structure and function of the protein is affected

Question 7

What is meant by base deletion?

Answer 7

A type of gene mutation when a nucleotide is lost from the DNA sequence

Question 8

What are the two possible effects of base deletion?

Answer 8

The amnio acid sequence of the polypeptide is different so the polypeptide cannot function correctly

One deleted nucleotide can cause all triplets on a sequence to be read differently because each has been shifted

Question 9

What is meant by chromosome mutations?

Answer 9

A change in the structure or number of whole chromosomes

Question 10

What two forms does chromosome mutations take?

1. 2.

Answer 10

1. Changes in whole sets of chromosomes
2. Changes in the number of individual chromosomes

Question 11

When does changes in whole sets of chromosomes occur?

Answer 11

It occurs when organisms have three or more sets of chromosomes instead of two

Question 12

What is an example of changes in whole sets of chromosomes and where does it mostly occur?

Answer 12

The condition polyploidy and occurs mostly in plants

Question 13

When does changes in the number of individual chromosomes occur?

Answer 13

It occurs when individual homologous pairs of chromosomes fail to separate during meiosis

Question 14

What is meant by the term ‘non-disjunction’?

Answer 14

It is when individual homologous pairs of chromosomes fail to separate during meiosis

Question 15

What does non-disjunction result in?

Answer 15

A gamete having either one more or one fewer chromosomes

Question 16

What is an example of non-disjunction in humans?

Answer 16

Down’s syndrome