Unit 2.3b

Question 1

What does diploid mean?

Answer 1

Cell in possession of two sets of chromosomes (2n=46haploid)

Question 2

What does haploid mean?

Answer 2

Cell in possession of a single set of chromosomes (n=23haploid)

Question 3

What does meiosis produce?

Answer 3

Genetic variable haploid cells that develop into gametes.

Question 4

Are cells genetically identical?

Answer 4

No, they are not, which increases variation

Question 5

What diploid cells are capable of carrying out meiosis?

Answer 5

Gametocytes

Question 6

Where are gametocytes found and what are they?

Answer 6

They are found in sex organs, in animals they’re in the ovaries and testes and in plants they are in the anther and ovaries I

Question 7

What are homologous chromosomes?

Answer 7

Pair of chromosomes of the same size, same centromere position, and with the same genes at the same loci

Question 8

What name is given to genes on the same chromosome ?

Answer 8

Linked genes

Question 9

What is the same on a homologous chromosome and what is different?

Answer 9

Genes are the same
Alleles of genes may be different

Question 10

Are homologous chromosomes inherited from the same parent?

Answer 10

No, one is maternal and one is paternal

Question 11

What must chromosomes do before meiosis can take place? (Stage 1.1)

Answer 11

Each chromosome must replicate to make two identical chromatids held together at the centromere

Question 12

What happens in stage two of the first part of meiosis? (1.2)

Answer 12

Chromosomes condense and homologous chromosomes pair up

Question 13

What happens in stage three of the first part of meiosis? (1.3).

Answer 13

Chiasmata form at points of contact between non-sister chromatids of a homologous pair and sections of DNA are exchanged
This random crossing over separates linked genes, and means new combinations of alleles can be produced

Question 14

What happens in stage four of the first part of meiosis? (1.4).

Answer 14

Spindle fibre is attached to homologous pairs of chromosomes, lining them up at the equator of the spindle
The orientation of pairs is random, this is called independent assortment.

Question 15

How can the number of different combinations of maternal and paternal chromosomes be calculated?

Answer 15

Using the formula 2n^
n = haploid number

Question 16

What happens in stage five of the first part of meiosis? (1.5)

Answer 16

The chromosomes in each homologous pair are split and move toward opposite poles
The sister chromatids remain attached

Question 17

What happens in stage six of the first part of meiosis? (1.6)

Answer 17

Cytokinesis occurs ie. the cytoplasm divides
Two daughter cells are formed

Question 18

What is produced in the second stage of meiosis?

Answer 18

Four haploid cells.

Question 19

What happens in stage one of the second part of meiosis? (2.1).

Answer 19

The nuclear membrane in each haploid daughter cell disintegrates

Question 20

What happens in stage two of the second part of meiosis? (2.2)

Answer 20

Chromosomes lineup singly on the equator

Question 21

What happens in stage three of the second part of meiosis? (2.3)

Answer 21

Sister chromatids separate and are randomly distributed to the daughter cells

Question 22

What happens in stage four the second part of meiosis? (2.4)

Answer 22

Cytokinesis takes place ie. the cytoplasm divide
Four genetically different haploid gametes produced