Meiosis

Question 1

What is meiosis

Answer 1

Meiosis is a type of cell division often referred to as the reduction division. during meiosis the daughter cells will have half of the original chromosome number of the parent cell. daughter cells are NOT GENETICALLY IDENTICAL.

Question 2

Why is meiosis necessary

Answer 2

To ensure that the cells of organisms formed by sexual reproduction have the correct number of chromosomes

Question 3

What is the difference between haploid and diploid in terms of chromosome number

Answer 3

diploid is 2n and haploid is n

Question 4

what is the difference between sex cells (gametes) and somatic cells (body cells)

Answer 4

Somatic cells are diploid and Sex cells are haploid.

Question 5

what is the difference between Gonosomes and Autosomes

Answer 5

Autosomes are chromosomes that are not the sex chromosome (Chromosome pair 1 - 22)

Gonosomes are the sex chromosomes (Pair 23)

Question 6

Where does meiosis take place in plants and animals

Answer 6

In animals,
Testes: In male
Ovaries: In female.

In plants,
Ovaries: In pistillate flowers
Anthers: In staminate flowers

Question 7

What happens during interphase before meiosis

Answer 7

DNA replication takes place chromosomes which are single threads become double. each chromosome contains 2 chromatids joined by a centromere. DNA replication helps to double the genetic material so that it can be shared by new cells arising from cell division.

Question 8

what happens during prophase 1

Answer 8

• Chromosomes shorten and become visible as two chromatids joined by a centromere.
• Homologous pairs of chromosomes are now visible.
• The nuclear membrane and nucleolus disappear.
• The spindle starts to form.
• Chromatids from each homologous pair touch. The point where they touch is called a chiasma.
• DNA is crossed over (swopped) at the chiasma.
• The spindle continues to form.

Question 9

what happens during metaphase 1

Answer 9

• The spindle extends across the whole cell.
• The homologous chromosome pairs line up along the equator of the spindle in their homologous pairs.
• One chromosome of each pair lies on either side of the equator.
• The centromere of each chromosome attaches to the spindle fibres.
random arrangement of chromosomes at the equator allows for genetic variation in the cells

Question 10

what happens during anaphase 1

Answer 10

• The spindle fibres shorten and pull each chromosome of each homologous chromosome pair to opposite poles of the cell.

Question 11

what happens during telophase 1

Answer 11

• The chromosomes reach the poles of the cell.
• Each pole has half the number of
chromosomes present in the original cell.
• The cell membrane constricts and divides the cytoplasm in half to form two cells.

Question 12

what happens during prophase 2

Answer 12

• Each cell formed during meiosis I now divides again.

* A spindle forms in each of the new cells.

Question 13

what happens during metaphase 2

Answer 13

• Individual chromosomes line up at the equator of each cell, with the centromeres attached to the spindle fibres.

Question 14

what happens during anaphase 2

Answer 14

• The spindle fibres start to contract.

* The centromeres split and CHROMATIDS are pulled to the opposite poles of each cell.

Question 15

what happens during telophase 2

Answer 15

• The SINGLE STRANDED UNREPLICATED CHROMOSOMES reach the
poles and a new nucleus forms.
• The cell membrane of each cell constricts and the cytoplasm divides into two cells.
• Four haploid cells are formed.
• Each new cell has half the number of
chromosomes of the original cell.
• The new cells are genetically different from each other.

Question 16

why is meiosis important

Answer 16

the process of meiosis reduces the number of chromosomes by half

the halving effect ensures that the number of chromosomes in the species stays the same over generations.

meiosis is important to introduce genetic variation

Question 17

name the processes and stages in which genetic variation is made possible during meiosis

Answer 17

crossing over-prophase 1
random arrangement-metaphase 1
(chromosomes arrange at the equator)
mutations during prophase 1 and anaphase 1

Question 18

what is down syndrome

Answer 18

Down syndrome is a abnormal disorder that is happens because of a meiosis division error where pair 21 has 3 chromosomes instead of 2. this results in a total of 47 chromosomes instead of 46.

Question 19

chromosome mutations: non-disjunction

Answer 19

Anphase 1-the 2 chromosomes of a homologous pair do not separate and one gamete has one chromosome too many (3 in total) and the other has 4 too many.

Question 20

aneuploidy

Answer 20

change in chromosome number

Question 21

what are the similarities between mitosis and meiosis

Answer 21

A type of cell division that forms daughter cells from a parent cell

takes place in the cell nucleus

stages are prophase, metaphase, anaphase and telophase

Question 22

what are the difference between mitosis and meiosis

Answer 22

mitosis- takes place in somatic cells
meiosis- takes place in sex cells

mitosis- the cell nucleus divides once
meiosis- the cell nucleus divides twice

mitosis- Two daughter cells are formed from one parent cell
meiosis- four daughter cells are formed from one parent cell

mitosis- chromosomes number remains constant
meiosis- chromosome number is halved

mitosis- exchange of genetic material/crossing over does not occur
meiosis- exchange of genetic material/crossing over does occur

Question 23

Why is crossing over important?

Answer 23

Crossing over brings about an exchange of genetic material during the process of gamete formation which results in the formation of new genetic combinations.
This results in formation of gametes that will give rise to individuals that are genetically different from their parents and siblings.