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 base sequence. Often arise spontaneously during DNA replication

Question 2

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

Answer 2

Genetic code is degenerate so mutation may end up coding for same amino acid as the original triplet

Mutation may occur in intron

Question 3

What is a substitution mutation

Answer 3

When a nucleotide in the DNA sequence is replaced by another. This is more likely to be a quiet mutation, meaning no change in the amino acid sequence

Question 4

What is a deletion mutation

Answer 4

When a nucleotide in the DNA sequence is lost. This is more likely to be harmful and significant, as it leads to a frame shift which means the entire amino acid sequence will be different

Question 5

What is mutagenic agent? Give examples of this

Answer 5

Factors that increase the rate of gene mutation. X-rays, UV light, gamma rays, certain chemical e.g. alcohol and tobacco

Question 6

What is a polyploidy chromosome mutation

Answer 6

Where an individual has three or more sets of chromosomes instead of two

Question 7

What is chromosome non-disjunction

Answer 7

When chromosomes fail to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal

Question 8

What is meiosis

Answer 8

A form of cell division that produces four genetically different haploid cells(cells with half the number of chromosomes found in the plant cell) known as gametes.

Question 9

How does meiosis differ from mitosis

Answer 9

Meiosis produces four genetically different cells with half the number of chromosomes as the parent cells

Question 10

What happens during meiosis 1

Answer 10

1. homologous chromosomes pair to form bivalents.
2. crossing over (exchange of section of genetic material) occurs at chiasmata
3. Cell divide into two with Homologous chromosomes separating randomly. Each cell contains either maternal or paternal copy

Question 11

What happens during meiosis 2

Answer 11

1. independent segregation of sister chromatids

2. Each cell divides again, producing 4 haploid cells

Question 12

In which two ways does meiosis produce genetic variation

Answer 12

1. Crossing over during meiosis 1
2. Independent assortment (random segregation) of homologous chromosomes and sister chromatids

Results in new combination of alleles