Component 2.2 - Mitosis

Question 1

Give an example of something with a haploid number of chromosomes

Answer 1

Human gamete

Question 2

Give an example of something with a diploid number of chromosomes

Answer 2

Human body cells

Question 3

What happens to the chromosomes offspring receive from each parent in humans?

Answer 3

They occur in matching pairs, called homologous pairs which are identical in size and shape and carry the same gene loci with genes for the same characteristic.

Question 4

What 3 stages is the cell cycle divided into?

Answer 4

Interphase
Mitosis
Cytokinesis

Question 5

What does mitosis produce?

Answer 5

Two daughter cells with the same number of chromosomes are genetically identical with each other and the parent cell.

Question 6

What occurs in the S phase of interphase?

Answer 6

This is where DNA replicates so the quantity doubles

Question 7

Why can you not see chromosomes in interphase?

Answer 7

The nuclear material, chromatin, is dispersed throughout the nucleus and has not condensed yet.

Question 8

What 4 stages make up mitosis?

Answer 8

Prophase
Metaphase
Anaphase
Telophase

Question 9

What happens in early prophase?

Answer 9

The chromosomes condense and coil, getting shorter and thicker and becoming visible and become visible as pairs of chromatids.

Question 10

What is the 1st step in late prophase?

Answer 10

Centrioles are present in animal cells and the pairs separate and mice to the opposite ends of the cell organising a partner as they move.

Question 11

What is the 2nd step of late prophase?

Answer 11

Protein microtubules form, radiating from each centriole and make the spindle. Spindle fibres extend from pole to pole and from pole to the centromere of each chromosome

Question 12

What happens in the 3rd step of late prophase?

Answer 12

The nuclear envelope disintegrates and the nucleolus dissapears

Question 13

What is the difference between pairs of chromosomes and pairs chromatids?

Answer 13

Chromatids are genetically identical but chromosomes are in pairs which are not genetically identical

Question 14

What happens in metaphase?

Answer 14

Chromosomes line up along the equator and attach to the spindle fibres at their centromeres.

Question 15

What can you see if you view metaphase from the pole?

Answer 15

The chromosomes appear spread out

Question 16

What can you see if you view metaphase from the side?

Answer 16

The chromosomes appear in a line

Question 17

What is the longest phase of mitosis?

Answer 17

Prophase

Question 18

When are chromosomes referred to as chromatids in the cell cycle?

Answer 18

Following their split at anaphase until telophase when they reach the poles of the cells.

Question 19

What happens in anaphase?

Answer 19

The centromeres separate and the spindle fibres shorten pulling the now separated chromatids to the poles, with the centromeres first.

Question 20

What happens in telophase?

Answer 20

Chromosomes uncoil and lengthen, the spindle fibres break down, the nuclear envelope re-forms and the nucleolus reappears

• This is the final stage of the division of the nucleus by mitosis

Question 21

What happens during cytokinesis in an animal cell?

Answer 21

A cleavage furrow forms by the constriction of the parent cell around the equator from the outside inwards

Question 22

What happens to a plant cell during cytokinesis?

Answer 22

Droplets of cell wall, a cell plate, form across the equator of the parent cell from the centre outwards and they extend and join the new cell wall.

Question 23

What is the difference between an animal and plant cell during mitosis (centrioles)?

Answer 23

Centrioles are present in animal cells but absent in plant cells

Question 24

Where does mitosis occur in plant cells?

Answer 24

Meristems (plants)

Question 25

How is producing genetically identically cells to the parent good?

Answer 25

Gives genetic stability

Question 26

What are the main functions of mitosis?

Answer 26

Growth in animals
Repair tissue
Replace dead cells
Increase in cell number in plants 
Asexual reproduction

Question 27

Where in adult mammals do cells need to be replaced by mitosis?

Answer 27

Nail beds, hair follicles, skin, gut lining, bone marrow

Instantly replaced from below

Question 28

What organisms reproduce by asexual reproduction?

Answer 28

Yeast, bacteria, some insects (greenfly) and some flowering plants where organs such as bulbs, tubers or runners produce identical offspring.

Question 29

What do genes do in the cell cycle?

Answer 29

Some of them ensure that mitosis happens where and when it is needed. These are called “tumour suppressor genes”

Question 30

What happens if the genes that control the cell cycle are damaged?

Answer 30

Cells may fail to divide, may divide too frequently or at the wrong time

Question 31

What are cancers the result of and what does this result in?

Answer 31

They are the result of uncontrolled mitosis. Cancerous cells divide repeatedly, out of control, with the formation of a tumour which is an irregular mass of cells.

Question 32

What can mutate DNA and cause the gene mutations that effect the timing of the cell cycle?

Answer 32

Radiation, certain chemicals, some viruses

Question 33

What are genes that have the potential to cause cancer called before they are mutated?

Answer 33

Photo-oncogenes

Question 34

What are genes that have the potential to cause cancer called after they are mutated?

Answer 34

Oncogenes