3.4.3 Genetic Diversity Can Arise

Question 1

What is a gene mutation

Answer 1

A change in the base sequence of DNA

Can arise spontaneously during DNA replication

Question 2

Types of mutation

Answer 2

Frame shift - addition/subtraction
Silent- no change in amino acid
Nonsense - substitution that creates a stop codon
Substitution - changes amino acids form another

Question 3

How can a mutation lead to the production of a non functional enzyme or protein

Answer 3

Change in the sequence of base triplets in DNA, changes sequence of codons on mRNA
Changes sequence of amino acids in polypeptide
Changes position of H, ionic, disulphide bonds between amino acids
Change in tertiary structure
In enzymes the active site has changed shape so cane form an enzyme-substrate complex

Question 4

Difference between haploid and diploid no.

Answer 4

Diploid- has 2 complete sets of chromosomes (2n) (26 for humans)
Haploid - has a single set of unpaired chromosomes (n) (23 for humans)

Question 5

Difference in meiosis 1 and 2

Answer 5

1) separated ominous chromosomes.
-they arrange into homologous pairs
-then cross over

2) separates chromatids

Question 6

How does crossing over create variation

Answer 6

Homologous pairs for a bivalent

Chiasmata form

Alleles exchange between chromosomes

Creating new combinations of alleles on chromosomes

Question 7

How does independent segregation work

Answer 7

Homologous pairs randomly align at the equator

Creating diffrent combinations of alleles in daughter cells

Question 8

How can genetic variation be increased without meiosis or mutation

Answer 8

Random fertilisation/fusion of genes

This creates new allele combinations and new chromosome combinations

Question 9

Differences in mitosis and meiosis

Answer 9

2 daughter cells vs 4

1 division vs 2

Mitosis maintains chromosome number - meiosis halves the chromosome number

Mitosis, genetically identical cells
Meiosis, genetically varied cells