Meiosis

Question 1

What are homologous chromosomes?

Answer 1

Matching chromosomes that contain the same genes in the same loci. They may have different alleles for some of these genes.

Question 2

What is meiosis?

Answer 2

The type of nuclear division that results in the formation of cells that contain half the number of chromosomes to the parent cell and are genetically not identical to the parent cell.

Question 3

Explain how sexual reproduction increases genetic variation.

Answer 3

It involves the combining of two unrelated individuals of the same species by fertilisation.

Question 4

Why is genetic variation within a population needed?

Answer 4

It increases its chances of survival when the environment changes as some individuals will be better suited to the changes.

Question 5

Im many organisms, the body cells are ….

Answer 5

Diploid

Question 6

For sexual reproduction to take place, the diploid cells must produce … ….

Answer 6

Haploid gametes

Question 7

What is produced when two gamete nuclei fuse?

Answer 7

A diploid zygote

Question 8

Where does meiosis take place?

Answer 8

In specialised organs called gonads- the ovaries and testes.

Question 9

Homologous pairs form with one ……and one ……. chromosome.

Answer 9

Maternal

Paternel

Question 10

In meiosis, how many divisions are there?

Answer 10

2

Question 11

How many chromosomes are there in the human body?

Answer 11

46

Question 12

What are the four stages in meiotic division 1?

Answer 12

prophase 1, metaphase 1, anaphase 1, telophase 1

Question 13

What are the four stages in meiotic division 2?

Answer 13

prophase 2, metaphase 2, anaphase 2, telophase 2

Question 14

The second meiotic division takes place at ……… ……… to the first.

Answer 14

Right Angle

Question 15

List all the ways meiosis produces genetic variation.

Answer 15

The crossing over in P1 shuffles the alleles. Independent assortment of the chromosomes in A1 and A2 makes the P+M chromosomes randomly distributed.
Haploid gametes are produces that can undergo random fusion with other organisms gametes.

Question 16

List the twelve stages of meiosis in order of how they take place.

Answer 16

Interphase 1, prophase 1, metaphase 1, anaphase 1, telophase 1, cytokinesis 1, interphase 2, prophase 2, metaphase 2, anaphase 2, telophase 2, cytokinesis 2.

Question 17

List four events that take place in the cell during interphase 1.

Answer 17

DNA replicated (s phase)
Organelles duplicated
Growth of cell (G1/2)
DNA replicate to produce sister chromatids.
Naked DNA not wound around just one proteins.

Question 18

List all the events that take place during Prophase 1 of meiosis.

Answer 18

Chromatids condense and chromosomes supercoil, the chromosomes come together in homologous pairs as crossing over occurs, nuclear envelope breaks down and spindles start to form from centrioles after the centrioles move to opposite poles, chromosomes get shorter and fatter as they condense.

Question 19

Explain all the events that take place in metaphase 1 of meiosis.

Answer 19

The chromosomes line up along the equator region as spindles attack to the centromere of the chromosomes and the chromosomes are INDEPENDENTLY ASSORTED as each of the pairs face opposite poles of the cell (randomly).

Question 20

Outline the events that take place in anaphase 1.

Answer 20

The chromosomes are separated from their homologous pairs as spindles move full chromosomes to the poles of the cell. They form v shaped as they’re pulled to the poles by the spindles contracting and each chromosome consists of two chromatids.

Question 21

Outline all the events happening in telophase 1.

Answer 21

Spindles reach the poles within the chromosomes and a new nuclear envelope starts to form around the two sets of chromosomes (in most animal cells).

Question 22

What three stages of Meiosis are skipped in most plant cells?

Answer 22

Telophase 1, cytokinesis 1 and interphase 2.

Question 23

Outline the events taking place in cytokinesis 1.

Answer 23

Nuclear division of the two cells- producing two haloed daughter cells that are genetically different.

Question 24

Outline the whets taking place in interphase 2.

Answer 24

Chromosomes uncoil and are very short.

Question 25

Outline the events taking place in prophase 2 of meiosis.

Answer 25

Spindles start to form from centrioles, nuclear envelope (made in T1) starts to break down, chromosomes condense and supercoil, u identical chromosomes due to the crossing over in P1 (NO CROSSING OVER).

Question 26

Outline the events taking place in metaphase 2 of meiosis.

Answer 26

Spindles attach to the centromeres of the chromosomes, perpendicular to the first division. Chromatids of each chromosomes are independently addicted and the arrangement determines how the chromatids separate in A2.

Question 27

Outline the events taking place in anaphase 2 of meiosis.

Answer 27

The centromeres of the chromosomes split, causing two separate chromosomes to be pulled to opposite poles of the cell (V shape) and the chromatids are randomly segregated.

Question 28

Explain the events taking place in telophase 2 of meiosis.

Answer 28

Four separate nuclear envelopes start to form around the sets of chromatids- forming a tetras of four haploid cells.

Question 29

Outline the events taking place in cytokinesis 2.

Answer 29

Cytoplasmic division occurs, producing four genetically different haploid gametes.

Question 30

Define ‘haploid’.

Answer 30

Having only one set of chromosomes and is represented by the symbol ‘n’.