Chapter 6- Cell Division

Question 1

What is mitosis?

Answer 1

A type of cell division that where cells produce identical copies of themselves

Question 2

What is mitosis used for?

Answer 2

Growth
Repair
Asexual reproduction

Question 3

What are the 4 distinct phases?

Answer 3

Prophase
Metaphase
Anaphase
Telophase

Question 4

What’s the first stage?

Answer 4

Interphase

Question 5

What are the 3 growth phases in interphase?

Answer 5

1. Gap phase 1 (G1)
2. Synthesis phase (S)
3. Gap phase 2 (G2)

Question 6

What occurs inn G1?

Answer 6

Cells grow bigger and replicates its organelles
High amounts of protein synthesis takes place in order to build new organelles

Question 7

What occurs in S phase?

Answer 7

Cell replicates its DNA

Question 8

What occurs in G2 phase?

Answer 8

Cells keep growing until all of the organelles have duplicated

Question 9

What happens when DNA replicates?

Answer 9

Each chromosome consists of 2 sister chromatids connected by the centromere

Question 10

What does mitochondria then produce?

Answer 10

Produces more ATP to provide energy for cell division
Ribosomes will be synthesising a high level of proteins to replicate organelles

Question 11

Where are the 2 ‘checkpoints’?

Answer 11

1. Before S phase
2. Straight after S phase

Question 12

What happens during the checkpoints?

Answer 12

The cell checks its DNA for errors

Question 13

What does the checkpoints prevent?

Answer 13

Minimises chances of duplicating any mutated DNA into replicated cell

Question 14

What occurs in prophase?

Answer 14

Chromosomes condense (shorter and fatter)
Nuclear envelope disintegrates
Centrioles move to opposite poles of cell and form spindle fibres

Question 15

What occurs in metaphase?

Answer 15

Chromosomes line up alone middle of cell
They attach to spindle fibres by centromere

Question 16

What occurs inn anaphase?

Answer 16

Centromere splits
Chromatids are pulled to opposite poles of the cell

Question 17

What occurs in telophase?

Answer 17

2 groups of chromosomes de-condense (long and thin)
Nuclear envelope reforms around them
Forming 2 new nuclei

Question 18

What occurs in cytokinesis?

Answer 18

Cytoplasm divides
Plasma membrane pinches off to form 2 new genetically identical cells

Question 19

How can we see mitosis happening?

Answer 19

Staining chromosomes in root tip cells and observing under a microscope
(Mitosis occurs in the meristem tissue)

Question 20

Method for observing mitosis?

Answer 20

1. Cut thing section of growing root tip tissue
   2.

Question 21

What are gametes?

Answer 21

Sex cells

Question 22

How may chromosomes in gametes?

Answer 22

They are haploid so contain half the number of chromosomes than the rest of the cells in our body
23 chromosomes

Question 23

Why is it haploid?

Answer 23

So when 2 gametes fuse during sexual reproduction fertilised egg (zygote) contain full number of chromosomes (46- 23 pairs)

Question 24

What happens during sexual reproduction?

Answer 24

Nucleus of sperm cell fuses with nucleus of egg cell

Question 25

What is fertilisation?

Answer 25

The fusion of nuclei

Question 26

What is meiosis?

Answer 26

Type of cell division which produces gametes for sexual reproduction

Question 27

What does meiosis produce?

Answer 27

Genetically different haploid cells

Question 28

What are the 2 rounds of meiosis?

Answer 28

1. Meiosis I 2. Meiosis II

Question 29

What occurs in interphase (MI) ?

Answer 29

DNA replicates 2 identical copies of each chromosome (chromatids)

Question 30

What occurs in prophase I ?

Answer 30

Chromatids condense Arrange into homologous pairs (bivalents) Crossing over occurs Nuclear envelope disintegrates Spindle fibres form

Question 31

What occurs in metaphase I ?

Answer 31

Homologous chromosomes line up along equator Attatch to spindle fibres by their centromeres

Question 32

What occurs in anaphase I ?

Answer 32

Homologous chromosomes are separated

Question 33

What occurs in telophase I ?

Answer 33

Chromosomes reach opposite poles Nuclear envelope reforms around chromosomes

Question 34

What occurs in cytokinesis ?

Answer 34

Thee result is formation of 2 daughter cells

Question 35

What occurs in prophase II ?

Answer 35

Chromosomes condense Nuclear envelope disintegrates Centrioles Spindle fibres form

Question 36

What occurs in metaphase II ?

Answer 36

Chromosomes attach to spindle fibres by their centromeres

Question 37

What occurs in anaphase II ?

Answer 37

Sister chromatids separate

Question 38

What occurs in telophase II ?

Answer 38

Chromatids reach opposite poles of cell Nuclear envelope reforms around

Question 39

What occurs after telophase II ?

Answer 39

Cytokinesis takes place 4 genetically unique daughter cells are produced

Question 40

Why is it important that organisms produce offspring with genetic variation?

Answer 40

If they are genetically similar they will all equally be vulnerable to the same diseases and other threats to survival

Question 41

What are 2 ways meiosis increases genetic variation?

Answer 41

1. Crossing over 2. Independent assortment

Question 42

Where does crossing over occur?

Answer 42

During prophase I

Question 43

What happens inn crossing over??

Answer 43

Homologous chromosomes move towards each other and exchange genetic material Chromatids from maternal chromosome twists around paternal chromosome and they connnect through chiasmata Pieces of chromosomes are exchanged and chromatids separate

Question 44

What does crossing over produce?

Answer 44

Chromosomes with different combination of alleles

Question 45

What happens during independent assortment?

Answer 45

Depending on order the chromosomes line up along the equator, (during metaphase) different combinations of chromosomes will end up in each gamete The way chromosomes align themselves on spindle fibres is random

Question 46

What does independent assortment result in?

Answer 46

Huge number of possibilities of chromosomal combinations in gametes