Genetic Diversity, Mutations and Meiosis

Question 1

What is a gamete?

Answer 1

Haploid sex cells

Question 2

What is a haploid cell?

Answer 2

A cell with a single set of unpaired chromosomes (one of each homologous pair)

Question 3

What is a diploid cell?

Answer 3

A cell with two complete sets of chromosomes (both homologous pairs - are from each parent)

Question 4

What is a homologous pair?

Answer 4

1. One chromosome form each parent
2. Same gene but different alleles

Question 5

What happens during Prophase 1 ?

Answer 5

1. Chromosomes condense
2. Nuclear membrane breaks down

Question 6

What happens during Metaphase 1?

Answer 6

1. Homologous pairs line up to the ends of each other
2. Spindle forms
3. Attaches to centromeres

Question 7

What happens during Anaphase 1 ?

Answer 7

1. Homologous pairs are separated
2. Pulled apart to opposite poles

Question 8

What happens during Telophase 1?

Answer 8

1. Nuclei reform over chromosomes
2. Cell divides

Question 9

What happens during Prophase 2?

Answer 9

1. Nuclei break down

Question 10

What happens during metaphase 2?

Answer 10

1. Chromosomes line up on the equator
2. Spindle forms
3. Attaches to centromeres

Question 11

What happens during Anaphase 2?

Answer 11

1. Chromatids are separated
2. Chromatids are pulled apart to opposite poles

Question 12

What happens during Telophase 2?

Answer 12

1. Nuclei reform around chromatids
2. Cells divide

Question 13

What is ‘crossing over’ ?

Answer 13

Different combinations of alleles
- Chromatids of homologous pairs cross over and swap alleles

Question 14

What is independent segregation?

Answer 14

Different combination of chromosomes

Question 15

What is a gene mutation?

Answer 15

Change to the base sequence of DNA during DNA replication

Question 16

What is gene substitution?

Answer 16

Swapping one base for a different base e.g G-T

Question 17

How can mutations cause a non - functional protein?

Answer 17

1. Change to DNA triplet during replication
   GGT -> GTT
2. Change to mRNA codon
3. Different anticodon ∴ different amino acid
4. Change to primary structure of protein
5. Different bonding e.g. Hydrogen / Ionic / Disulphide Bonds
6. ∴ Tertiary structure change

Question 18

How can DNA mutate and there be no change to the primary structure?

Answer 18

1. DNA is degenerate
2. Each amino acid is coded for by more than one triplet codon
3. Change to DNA base (substitution) might not cause a change to amino acid in primary structure GGT -> GGC
4. No change to bonding or tertiary structure