3.4.3 Genetic diversity can arise as a result of mutation or during meiosis

Question 1

What is a Mutation?

Answer 1

An alteration to the DNA sequence and often occurs spontaneously during DNA replication

Question 2

Why might a mutation not lead to a change in the amino acid sequence?

Answer 2

• Mutation may occur in the intron
• Genetic code is degenerate so mutation may just end up coding for the same amino acid as the original triplet

Question 3

What is a Deletion mutation?

Answer 3

When a nucleotide from a DNA sequence is lost which can be harmful as it leads to a frameshift so changes the amino acid sequence

Question 4

What is a Substitution mutation?

Answer 4

When a nucleotide from a DNA sequence is replaced with another and is normally a quiet mutation as it doesn’t change the amino acid sequence

Question 5

What is a Mutagenic agent?

Answer 5

Factors that increases the rate of gene mutation
- X-rays
- UV light
- Gamma rays
- Chemicals like tobacco and alcohol

Question 6

What is a Polyploidy chromosome mutation?

Answer 6

When an individual has 3 or more sets of chromosomes instead of 2

Question 7

What is Chromosome non-disjunction?

Answer 7

When chromosomes fail to separate correctly during meiosis causing gametes to have 1 more or 1 less chromosome than normal

Question 8

What is Meiosis?

Answer 8

A form of cell division that produces 4 genetically different haploid cells known as gametes

Question 9

What are Haploid cells?

Answer 9

Cells with half the number of chromosomes found in the parent cell

Question 10

How does Meiosis differ from Mitosis?

Answer 10

• Meiosis produces 4 genetically different cells with half the number of chromosomes as the parent cells
• Mitosis produces 2 genetically identical cells with the same number of chromosomes as the parent cells

Question 11

What happens during Meiosis I?

Answer 11

• Homologous chromosomes pair to form bivalents
• Crossing over (exchange of section of genetic material) occurs at the chiasmata
• Cell divides into 2. Homologous chromosomes separate randomly. Each cell contains either the maternal or paternal copy.

Question 12

What happens during Meiosis II?

Answer 12

• Indépendant segregation of sister chromatids
• Each cell divides again , producing 4 haploid cells

Question 13

Give 2 ways Meiosis produces genetic variation

Answer 13

• Crossing over during meiosis I
• Independent assortment (random segregation) of homologous chromosomes and sister chromatids
• These both result in new combinations of alleles