9.2 - Mutations in chromosome number

Question 1

What happens when abnormal gametes take place in fertilisation? Use Down’s Syndrome as an example:

Answer 1

• a chromosome mutation occurs as the diploid cell will have the incorrect no. of chromosomes
• an example is Down’s syndrome - individuals have a total of 47 chromosomes as they have 3 copies of chromosomes within the 21st pair

Question 2

What do chromosome mutations normally involve?

Answer 2

normally involves with a extra copy or no. of copies of one chromosome within a gamete
* has a different number of chromosomes compared to the normal haploid number

Question 3

What are non-disjunction mutations?

Answer 3

occurs when chromosomes fail to separate during meiosis
* occurs spontaneously