Unit 1.5b

Question 1

Why can living organisms reproduce?

Answer 1

Because our cells can divide

Question 2

How long does it take prokaryotes, like bacteria, to divide?

Answer 2

It can be as short as 20 minutes

Question 3

How long does it take eukaryotes to divide?

Answer 3

On average, it takes around 24 hours

Question 4

Why does it take so long for eukaryotes to divide in comparison to prokaryotes?

Answer 4

Because they go through the cell cycle, which is more complex

Question 5

Why is the cell cycle complex in comparison to other ways cells divide?

Answer 5

It’s more complex due to organelles and the cell having lots of chromosomes containing DNA and proteins

Question 6

What is the complex containing DNA and proteins in chromosomes called?

Answer 6

Chromatin

Question 7

Why is cell division important in multicellular organisms?

Answer 7

It allows cells to grow and replace dead cells, which therefore repairs damaged tissues

Question 8

What is the cell cycle?

Answer 8

It’s to process in which a cell goes through to duplicate its content

Question 9

What is the product of the cell cycle?

Answer 9

Two genetically identical daughter cells

Question 10

Do all cells need to be replicated at the same rate?

Answer 10

No, some cells will be replicated more often than others due to the need for being replaced and some will never replicate

Question 11

Why do some cells never divide?

Answer 11

Some cells never divide as they are so specialised

Question 12

What causes cells in the liver to divide?

Answer 12

They must be stimulated

Question 13

How is the cell cycle regulated?

Answer 13

Cell cycle is regulated by control system which responds to intra an extra cellular signals

Question 14

What would happen if the rate of the cell cycle is altered?

Answer 14

There would be serious consequences

Question 15

What is a proto-oncogene?

Answer 15

It’s a normal gene often involved in the control of cell growth and division

Question 16

What is formed when a proto-oncogene mutates?

Answer 16

A tumour-promoting oncogene is formed

Question 17

What do tumour promoting oncogenes cause?

Answer 17

They cause the cell to divide in an uncontrolled and unregulated manner

Question 18

What is the result of an uncontrolled increase in the cell cycle?

Answer 18

Tumour formation, as without regulation, the cells are not recognised and attacked by the immune system which leads to cancer

Question 19

What is the result of an uncontrolled reduction in the cell cycle?

Answer 19

Degenerative diseases as neurons re-enter the cell cycle, but cannot complete it which means the cell will die

Question 20

What are the two main phases the cell cycle is broken into?

Answer 20

The interphase and the mitotic (M) phase

Question 21

What happens during the interphase?

Answer 21

Cell growth and DNA replication

Question 22

What occurs during the mitotic phase?

Answer 22

Segregation of replicated chromosomes, and the division of the cytoplasm, which leads to the formation of daughter cells

Question 23

What is three sub phases, make up the interphase?

Answer 23

1. G1
2. S Phase
3. G2

Question 24

What occurs during the G1 phase?

Answer 24

This is the first period of growth where proteins and organelles are synthesised. As the cell is active, it carries out metabolic processes.

Question 25

What occurs during the S phase?

Answer 25

Cell growth continues
The nuclear DNA replicates
Chromosomes are copied in preparation for mitosis leading to chromosomes becoming sister chromatids

Question 26

What occurs during the G2 phase?

Answer 26

This is the second growth period where proteins and organelles are again synthesised

Question 27

By the end of interphase, what has happened to the parent cell?

Answer 27

The size of the parent cell will have doubled

Question 28

Is interphase part of mitosis?

Answer 28

No, interphase is part of the cell cycle

Question 29

What is the mitotic phase split into?

Answer 29

It’s split into mitosis and cytokinesis

Question 30

What happens during mitosis? (tiny summary)

Answer 30

The nucleus and its contents divide equally

Question 31

What happens during cytokinesis? (Tiny summary)

Answer 31

Separation of cytoplasm into daughter cells

Question 32

In order, what are the four stages of mitosis?

Answer 32

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Question 33

How are the four stages of mitosis recognised?

Answer 33

They are recognised by their appearance, and the location of the cells chromosomes in its nucleus

Question 34

What occurs during prophase?

Answer 34

• DNA condenses into chromosomes with two sister chromatids
• The nuclear membrane breaks down and spindle microtubules extend from the MTOC by polymerisation
• The spindle fibres attach to the chromosomes at the kinetochores in the centrosome

Question 35

What is the kinetochores?

Answer 35

It’s the joining site in the centromere

Question 36

What occurs during metaphase?

Answer 36

Chromosomes align at the metaphase plate

Question 37

What is the metaphase plate?

Answer 37

It’s the arrangement of chromosomes at the cell equator

Question 38

What occurs during anaphase?

Answer 38

Spindle microtubules shorten by depolymerisation separating the sister chromatids and pulling them to opposite poles

Question 39

What occurs during telophase?

Answer 39

-Chromosomes decondense and nuclear membranes form around them
-This is also when is cytokinesis occurs

Question 40

What occurs during cytokinesis in animal cells?

Answer 40

A protein ring around the centre of the cell contracts pinching it into two genetically identical daughter cells each with one nucleus

Question 41

What equation allows us to work out the percentage of cells in a sample undergoing mitosis?

Answer 41

(Cells in mitosis (PMAT) / total number of cells) x 100