Mitosis And Meiosis

Question 1

What are the stages of the cell cycle and what happens in each? (Simply)

Answer 1

G1-cell contents replicated
S-DNA replicated
G2-cell grows in size
M-mitosis/meiosis (cell division)

Question 2

What is a telomere?

Answer 2

A repeated equine of base ate each end of a chromosome/chromatid (can be used as a marker as is known)

Question 3

What is a centromere?

Answer 3

It links the sister chromatids and is made of repeating sequences.

Question 4

How are chromosomes grouped by scientists?

Answer 4

According to size and shape

Question 5

What is the basic of mitosis?

Answer 5

Cell division for Somatic cells.
Produces 2 identical daughter cells (same chromosome content as parental cell)
Mitotic growth is needed constantly for tissues such as epidermis and bone marrow

Question 6

What are the stages of mitosis?

Answer 6

Prophase
Premataphase
Metaphase
Anaphase
Telophase

Then cytokinesis

Question 7

Describe prophase.

Answer 7

Nuclear membrane dissolves
Chromosomes are visible
Kinetochore proteins bind to centromere
Spindle fibres form

Question 8

Describe premetaphase.

Answer 8

The spindle fibres attach to the kinetochore’s

Question 9

Describe metaphase.

Answer 9

Chromosomes randomly line up at metaphase plate (middle of cell)

Each chromosome has 2 chromatids

Question 10

Describe Anaphase.

Answer 10

The kinetochore fibres pull the daughter chromasomes apart separating the chromosomes and breaking the centromere

Question 11

Describe telophase.

Answer 11

The cytoplasm divides (using cleavage furrow) and the nuclear envelope reforms.

2 daughter cell are formed (containing same genetic info as parent)

Question 12

What are homologous chromosomes?

Answer 12

Have the same DNA sequence and genes

However the gee may be different variants of each other (alleles)

Question 13

What is a sister chromatid?

Answer 13

Has the identical DNA and same alleles as they are replications of each other

Question 14

What are non-sister chromatids?

Answer 14

Have the same genes, but different alleles (not replicated)

Question 15

What is meiosis main points?

Answer 15

Cell division for germ line cells (sex cells)
Produce 4 non0identical haploid cells
One lot of replication and 2 divisions
Produced gametes

Question 16

What are the stages of meiosis?

Answer 16

Meiosis 1 = prophase 1, metaphase 1 (this is when variation occurs), anaphase 1, telophase 1

Meiosis 2= prophase 2, metaphase 2, anaphase 2, telophase 2

Question 17

What happens in prophase 1 of meiosis?

Answer 17

The pairs of chromatids find each other.

Question 18

What happens in metaphase 1 of meiosis?

Answer 18

The homologous pairs of chromosomes form tetrads. And line up at metaphase plate. Recombination occurs as does random assortment

Question 19

What is recombination?

Answer 19

Chromatids with near identical sequence find each other.
The chiasmata of these chromosomes can now cross over and so genetic info is swapped. The daughter chronometer are now non identical.

(If sister chromosomes cross this doesn’t matter but it has no effect as they are indentical)

Question 20

What happens in anaphase 1 of meiosis?

Answer 20

The homologous pairs are pulled apart (pairs seperate not chromosomes)

Question 21

What happens in telophase one of meiosis?

Answer 21

The two daughter cells form

Each is a haploid cell with 23 unreplicated chromosomes

Question 22

Hat happens in prophase 2 of meiosis?

Answer 22

The homologous pairs are still crossed over from prophase 1. The envelope disintegrates

Question 23

What happens in metaphase 2 of meiosis?

Answer 23

The chromosomes pair up randomly. No homologous pairs are present (only 23 in each cell no replicated)

Question 24

What happens in anaphase 2 of meiosis?

Answer 24

The chromatids are separated by spindle fibres and pulled to poles.

Question 25

What happens in telophase 2 of meiosis?

Answer 25

Envelope reforms and 4 (2 per telophase 2) non-identical daughter cells are created.

Question 26

What does meiosis ensure?

Answer 26

Maintains constant number of chromosomes in every generation ( 23 per gamete fuse so 46 per cell)

Generate genetic diversity (random assortment of chromosomes and crossing over of genetic material)

Question 27

What happen in Spermatogeneis? (Brief overview)

Answer 27

One spermatocyte produced 4 non identical sperm.

Takes around 60 days.

Question 28

What happens in oogenesis? (Brief overview)

Answer 28

One oocyte produces 1 egg and 3 polar bodies

Takes between 12-50 years