3.4.3 Genetic Diversity by Mutation or Meiosis

Question 1

What are the two types of cell division?

Answer 1

Mitosis: produces two diploid cells
Meiosis: produces four haploid cells

Question 2

How many chromosomes do gametes have?

Answer 2

Haploid (half the number of a normal body cell)

Question 3

What are the two divisions during Meiosis? (No explanation)

Answer 3

Meiosis 1

Meiosis 2

Question 4

What is a gene?

Answer 4

A length of DNA that codes for a polypeptide

Question 5

What is a locus?

Answer 5

The position of a gene on a chromosome or DNA molecule

Question 6

What is an allele?

Answer 6

One of the different forms of a particular gene

Question 7

What are homologous chromosomes?

Answer 7

A pair of chromosomes, one maternal, one paternal with the same gene loci

Question 8

What is fertilisation?

Answer 8

The fusion of a male and female gamete

Question 9

What is the process of prophase 1?

Answer 9

Chromosomes condense and become visible
Nuclear envelope breaks down
Contains 4n genetic material

Question 10

What is the process of metaphase 1?

Answer 10

Homologous pairs of chromosomes line up next to each other
Spindle fibres connect to the centrioles
Contains 4n genetic material

Question 11

What is the process of anaphase 1?

Answer 11

Homologous pairs are pulled apart to opposite poles of the cell
Contains 4n genetic material

Question 12

What is the process of telophase 1?

Answer 12

Nuclei reform
Cytokinesis
Forms two cells with 2n genetic material each

Question 13

What is the process of prophase 2?

Answer 13

Nuclei break down

Contains 2n genetic material

Question 14

What is the process of metaphase 2?

Answer 14

Chromosomes lime up on the equator of the cell
Spindle fibres attach to the centromeres
Contains 2n genetic material

Question 15

What is the process of anaphase 2?

Answer 15

Chromatids are separated by the contraction of the spindle fibres
They’re pulled apart to opposite poles
Contains 2n genetic material

Question 16

What is the process of telophase 2?

Answer 16

Nuclei reform
Cell divides
Produces n genetic material per cell

Question 17

What are the two forms of variation during meiosis? (No explanation)

Answer 17

Independent segregation

Crossing over

Question 18

What is the process of independent segregation?

Answer 18

The homologous chromosomes randomly line up in meiosis 1 along the equator so the chromosomes at the poles are randomly selected

Question 19

What is the process of crossing over?

Answer 19

During meiosis 1, the chromatids become twisted round each other
The twisting creates tension where portions are broken off
These portions rejoin with the partner chromatids
Usually equivalent portions of homologous chromosomes are exchanged
This creates new genetic combinations

Question 20

What is the aim of meiosis?

Answer 20

To create gametes (haploid cells) with half the number of normal chromosomes
To create sperm and ovum
To introduce variation

Question 21

What is a substitution reaction?

Answer 21

A nucleotide in a DNA molecule is replaced by another nucleotide that has a different base
This changes the amino acid and disrupts the primary structure
This could mess up the whole chain because the R groups affect the secondary and tertiary structure
A mutation could give you exactly the same amino acid and have little or no effect
It can change an enzyme’s active site so that it doesn’t work

Question 22

What is a deletion mutation?

Answer 22

DNA bases shift to the left which completely changes the sequence, stops the polypeptide from functioning

Question 23

What is meant by random fertilisation?

Answer 23

Any egg can be fertilised by any sperm which increases variation

Question 24

What is crossing over?

Answer 24

When portions of DNA are swapped between non-sister chromatids

Question 25

What is the role of the centromere during mitosis?

Answer 25

Centromere attaches to the spindle fibres

It allows separation in anaphase as centromere splits