B1 Chromosomes and Mitosis (page 15)

Question 1

In order to survive and grow, what do our cells have to do?

Answer 1

they have to be able to divide and grow, that means our DNA as well

Question 2

What do Chromosomes contain?

Answer 2

Genetic Information

Question 3

Most cells in your body have a nucleus. what is the Nucleus?

Answer 3

The nucleus contains your genetic material in the form of chromosomes.

Question 4

What are Chromosomes?

Answer 4

they are coiled up lengths of DNA molecules.

Question 5

Each Chromosome carries a large number of what?

Answer 5

Genes.

Question 6

What are Genes?

Answer 6

they control the development of different characteristics, e.g. hair colour.

Question 7

Body cells normally have two copies of each chromosome, where are the chromosomes from?

Answer 7

one copy from the organism’s ‘mother. and one from its ‘father’.

So, humans have two copies of cromosome 1, two copies of chromosome 2, etc

Question 8

How many chromosomes pairs does a human cell have?

Answer 8

23 pairs of chromosomes.

Please look at diagram of the 23 chromosomes on page 15.

Question 9

What is the Cell Cycle for?

Answer 9

it makes new cells for growth, development and repair.

Question 10

What happens in the Body cells in multicellular organisms?

(multicellular means more than one cell)

Answer 10

they divide to produce new cells as part of a series of stages called the cell cycle.

Question 11

What is the stage of the cell cycle called, when the cell divides?

Answer 11

It is called Mitosis.

Question 12

Why do Multicellular organisms use mitosis?

Answer 12

to grow or replace cells that have been damaged.

Question 13

What happens at the end of the cell cycle?

Answer 13

it results in two new cells identical to the original cell with the same number of chromosomes.

Question 14

What are the main two stages of the cell cycle?

(you need to know about these)

Answer 14

Growth & DNA Replication
Mitosis

Please see diagram on page 15 of cells and mitosis.

Question 15

Regarding Growth & DNA Replication?

In a cell that’s not dividing what do the DNA look like?

Answer 15

The DNA is all spread out in long strings.

Question 16

Regarding Growth & DNA Replication

Before the cell divides, the cell has to grow and increase what?

Answer 16

the amount of subsellular structures, such as mitochrondria and ribosomes.

Question 17

Regarding Growth & DNA Replication

Once the cell has grown, what happens?

Answer 17

it then duplicates its DNA - so there’s one copy for each new cell. The DNA is copied and forms x-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other

(the left arm has the same DNA as the right arm of the chromosome).

Question 18

Once the cells contents and DNA have been copied, the cell is ready for what?

Answer 18

Mitosis.

Question 19

What is the first step of mitosis?

Answer 19

the chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell.

Question 20

Once the two arms of each chromosome go to opposite ends of the cell, what happens next?

Answer 20

Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has divided.

Question 21

What is the last process of mitosis?

Answer 21

lastly, the cytoplasm and cell membrane divide.

The cell has now produced two new daughter cells. The daughter cells contain exactly the same DNA - they’re identical. Their DNA is also identical to the parent cell.

(Please look at the picture diagram on page 15, as you may be asked to draw the cells in the exam)