Chapter 15 Heridity I

Question 1

Define the term mutation [1] (2011/A2)

Answer 1

It is the spontaneous change in the structure of a gene or chromosome.

Question 2

State two causes of mutation [2] (2011/A2)

Answer 2

Radiation eg; exposure to UV rays, gamma rays [1] /
Chemicals eg; formaldehyde, mustard gas [1]
(if state 2 examples of radiation, only 1 mark is given)

Question 3

Describe what is meant by mutation [1] (2016/A3)

Answer 3

Spontaneous/Sudden change to the structure of genes and chromosomes and chromosome
numbers

Question 4

Using named examples, explain what is meant by a mutation [4] (2017/B10 ORb)

Answer 4

A mutation is a random/ spontaneous change in either the DNA sequences leading to a gene
mutation [1] or a change in the structure or the number of
chromosomes, leading to a chromosomal mutation.[1]

In the inheritance of sickle cell anaemia, an example of gene mutation, a change in a single nucleotide in the DNA sequence of the gene that codes for haemoglobin. [1]
This results in a change in the shape of the haemoglobin molecule causing them to clump together in the red blood cell. [1]
OR
When there is an extra number of
chromosome in position 21 of the karyotype, there are 3 chromosomes instead of 2. The individual will end up with a total of 47 chromosomes [1]
resulting in the individual inheriting the condition Down’s Syndrome with mild to moderate or severe intellectual disabilities