Mitosis and Meiosis Part 2

Question 1

Where is Meiosis seen

Answer 1

Meiosis is a special type of cell division for germline cells. (The cells that form eggs in females and sperm in males.)

Question 2

What does Meiosis Produce

Answer 2

Meiosis produces four non-identical cells with half the chromosome complement of the parental cell

One round of replication is followed by TWO rounds of cell division (meiosis I and meiosis II)

A diploid (2n) cell becomes haploid (n)

Question 4

How long can prophase last in mammals

Answer 4

Prophase can last up to several days in mammals! Recombination takes time

Question 5

What are the stages of Meiosis 1

Answer 5

Prophase. 1
Metaphase. 1
Anaphase. 1
Telophase. 1

Question 6

What happens in prophase 1

Answer 6

Nuclear membrane reforms

Chromosome decondense

Cytokinesis occurs

During prophase I homologous chromosomes pair
up (bivalents)

Crossing over occurs (chiasmata)

Recombinant chromosomes are formed

Question 7

What happens is recombination

Answer 7

In bivalent forms, crossing over occurs, this produces genetically different daughter chromosomes,
(switch in alleles)

Question 8

What happens in Metaphase 1

Answer 8

Spindle forms and chromosomes line up at centre of cell at the Metaphase Plate

Question 9

What happens in anaphase 1

Answer 9

Kenesin motors move two halves of the chromosomes to each side of the cell
(Chromosomes migrate to either side of cell)

Question 10

What happens in Telophase 1

Answer 10

Nuclear membrane reforms

Chromosome decondense

Cytokinesis occurs

A cleavage furrow forms turns cells in to two daughter cells

Question 11

What happens in Meiosis II

Answer 11

Prophase. 2
Metaphase. 2
Anaphase. 2
Telophase. 2

In meiosis II the same steps take place but without DNA
replication

Chromosomes separate to form chromatids

Question 12

What number of chromosome are produced from Meiosis II

Answer 12

cells that are produced have half the number
of chromosomes - haploid

Question 13

What are the stages of prophase I
what are they

Answer 13

Leptotene,- Chromosomes condense
Zygotene, - Synapsis between different homologous chromosomes (where they bind to eachother)
Pachytene, - Crossing over
Diplotene, - Dissolution of Synaptonemal Complex
Diakinesis. - Dissolution of nuclear Membrane once recombination has occurred

Question 14

What is the consequences of Meiosis

Answer 14

Maintaining constant number of chromosomes from generation to generation -
Generation of genetic diversity:
1.Random assortment of chromosomes
2.Crossing over of genetic material

Question 15

Meiosis in males - spermatogenesis
what is this

Answer 15

1 spermatocyte (2n) gives rise to 4 sperm (n)

Length of spermatogenesis is ~60 days

Question 16

Meiosis in females - oogenesis
What is this

Answer 16

1 oocyte (2n) gives to rise to 1 egg (n) + 3 polar bodies ( these aren’t used in reproduction)

Length of oogenesis is 12-50 years!

Question 17

What is caused by Non-Disjunction during Meiosis

Answer 17

Aneuploidy is the condition of having an abnormal number of chromosomes in a haploid organism

Aneuploidy can be caused by non-disjunction during mitosis or meiosis.

A failure to separate pairs of chromosomes lined up at the metaphase plate can produce daughter cells with abnormal chromosome numbers

(1 chromosome instead of 2) - Mosaicism
(3 chromosomes instead of 1) - Trisomy

Question 18

What is Non-Disjunction

Answer 18

Unequal distribution of chromosomes caused by failure to segregate properly during meiosis

Question 19

Difference between gene and allele

Answer 19

an allele is a variant form of a gene.