Cell Division /Cell Cycle

Question 1

types of cell division

Answer 1

mitosis (one cell splitting into two cells)
meiosis

Question 2

what is mitosis part of

Answer 2

Mitosis is part of a much longer process called the cell cycle

Question 3

What does duration of cell cycle depend on

Answer 3

cell cycle can take a long time (duration of cell cycle depends on type of cell)

Question 4

Is it possible for some cells to exit the cell cycle

Answer 4

Some cells can exit the cell cycle, either temporarily or permanently

Question 5

General Stages of cell cycle - NAMES.

Answer 5

M (mitotic) phase - when mitosis takes place and cell divides into two
M phase relatively short period within whole cell cycle

Most of cell cycle is called interphase - cell may appear to be relatively inactive but lots of different processes are happening

During interphase, the cell is also carrying out the functions of that particular cell type e.g. intestinal epithelial cells are absorbing nutrients from the small intestine

Interphase can be divided into three phases - G1, S, G2 phase

Question 6

Stages of interphase (in cell cycle) - G1. describe what happens

Answer 6

The first stage is called the G1 phase. During the G1 phase, the cell replicates organelles such as mitochondria

Replicating organelles requires a lot of proteins. So during G1, a high level of transcription and translation takes place

During G1 phase the size of the cell also increases. This ensures that when the cell divides, the two daughter cells are the correct size

Question 7

explain why it is important for the cell size to increase during the G1 phase

Answer 7

During G1 phase the size of the cell also increases. This ensures that when the cell divides, the two daughter cells are the correct size

Question 8

explain why lots of translation and transcription occurs in G1 phase

Answer 8

The first stage is called the G1 phase. During the G1 phase, the cell replicates organelles such as mitochondria

Replicating organelles requires a lot of proteins. So during G1, a high level of transcription and translation takes place

Question 9

Stages of interphase (in cell cycle) - S. Describe what happens

Answer 9

After G1 (next), the cell passes into the S (Synthesis) stage.

During the S phase, all of the chromosomes are replicated

To do this, the cell needs to synthesise a lot/large amount of DNA.

Lots of DNA synthesis occurs

Question 10

explain why lots of DNA synthesis occurs in S phase of Interphase

Answer 10

During the S phase, all of the chromosomes are replicated

To do this, the cell needs to synthesise a lot/large amount of DNA.

Lots of DNA synthesis occurs

Question 11

Describe what happens in G2 (INTERPHASE IN CELL CYCLE)

Answer 11

Now the cell enters the G2 phase.

During G2, the cell replaces the energy stores used during the S phase. (energy stores increase)

The cell also continues to carry out transcription and translation

If any of the chromosomes have been damaged, then they are repaired during G2

Just like in the G1 phase, the cell continues to grow (size of cell increases)

Question 12

What happens when cell finishes G2 stage

Answer 12

Once the cell has finished the G2 phase, it now enters the M (Mitotic phase)

Question 13

The mitotic phase can be divided into two parts. / cell carries out two processes in mitotic phase. These are:

Answer 13

The mitotic phase can be divided into two parts:
In mitotic phase cell carries out two processes

Mitosis (where chromosomes separate into two nuclei)

The first part is called mitosis
during mitosis - chromosomes are separated into two nuclei

nucleus divides into two daughter nuclei

second part cytokinesis
during cytokinesis - cell divides into two
Cytokinesis (cell divides into two)

cell divides into two daughter cells each with a nucleus

Question 14

What phase is the cell in if it exits the cell cycle

Answer 14

Sometimes cells can exit the cell cycle.
If this happens, then it is said that the cell is in the G0 phase

Question 15

Reasons why cells enter G0. (subscript 0)

Answer 15

Fully differentiated cells enter G0 and stay there for the rest of their lives. For example neurons in adults (once reached maturity, fully differentiated, they never need to divide again) - also cardiac cells

Over time, the DNA in cells can be damaged. At a certain point the cell will no longer be able to divide. These cells are called Senescent cells
At this stage, the cell enters G0 permanently

Some cells enter G0 temporarily e.g. B memory cells
These cells can then be triggered to re-enter the cell cycle during an infection

Question 16

Explain how the cell cycle is very tightly regulated

Answer 16

The cell cycle is very tightly regulated

At certain key points in the cell cycle, the cell checks that the cell cycle should continue

These are called checkpoints.

At any point, if a cell fails a check point, it will leave the cell cycle and enter G0.

Question 17

How many checkpoints are there. Describe them

Answer 17

There are three check points.

Before the S phase, the cell must pass through the G1 checkpoint.

Here the cell checks that it has grown to the correct size. Also checks for DNA damage

If the cell satisfies the G1 checkpoint, then it passes into the S phase and carries out DNA replication

The next check pint is at the end of G2 before cell passes into the Mitotic phase.
At G2 checkpoint, the cell checks for DNA damage and cell has grown to the correct size

If this checkpoint is passed, then the cell moves into the Mitotic phase

The final checkpoint is called the metaphase checkpoint or spindle checkpoint

This checks that the chromosomes are assembled correctly n the mitotic spindle.

If this is the case/passes this checkpoint, then the cell completes mitosis and proceeds through cytokinesis

Question 18

Draw a diagram showing the cell cycle

Answer 18

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTmyvL26jtcYAReJ9GcYNdGFlBiMVVkMWM_Qg&s

Question 19

what are diploid cells

Answer 19

Cells which contain chromosomes in pairs

Question 20

in most organisms including humans, what type of cell are virtually all of the cell

Answer 20

In most organisms, including humans, virtually all of the cells are diploid

Question 21

in cell division by mitosis we start with ______ diploid cell and end up with _____ _______ diploid cells

Answer 21

in cell division by mitosis we start with ONE diploid cell and end up with TWO IDENTICAL diploid cells

Question 22

describe the roles of mitosis in living organisms / purpose of mitosis

Answer 22

Cell division by mitosis takes place when we want identical copies of a cell e.g. when an organism grows or repairs itself

Used for asexual reproduction

Question 23

division of nucleus is called ______
division of cell is called _____

Answer 23

division of nucleus is called mitosis

division of the cell is called cytokinesis

Question 24

when do both mitosis and cytokinesis occur

Answer 24

Both mitosis and cytokinesis occur/take place during the M phase of the cell cycle

Question 25

what cannot be seen during interphase, what can be seen instead?

Answer 25

During interphase, chromosomes cannot be seen in the nucleus.
The chromosomes are there, but they are not visible as distinct structures.

Instead this dark material can be seen, which is called chromatin

Question 26

describe the structure of chromatin

what does the structure of chromatin allow for.

Answer 26

In chromatin, the chromosomes have a loose open structure

This means that the DNA is accessible for transcription and translation (replication)

Question 27

what is a chromosome

Answer 27

A chromosome is a single long molecule of DNA

Question 28

draw a diagram showing how chromosomes are replicated during interphase

Answer 28

https://images.nagwa.com/figures/explainers/650191397968/16.svg

—–> = DNA replication during interphase

Question 29

what happens when chromosomes are replicated during interphase

Answer 29

When chromosomes are replicated during interphase, there is now (we now have) two identical molecules of DNA

These are called sister chromatids - they are identical
The point where the sister chromatids are joined is called the centromere

Question 30

what is each chromosome in the chromosome pair called - when DNA replication during interphase has occured

Answer 30

each chromosome in the chromosome pair is called sister chromatids

Question 31

what is the centromere

Answer 31

The point where the sister chromatids are joined is called the centromere

Question 32

https://images.nagwa.com/figures/explainers/650191397968/16.svg

—–> = DNA replication during interphase

how often does DNA replication occur

Answer 32

The process of DNA replication during interphase happens for every chromosome - happens for each of 46 chromosomes (23 pairs) in humans

Question 33

when does DNA replication take place, what is special about the chromosomes

Answer 33

DNA replication takes place during interphase

Chromosomes are not visible as distinct structures at this stage