3.2.5 Cell Division

Question 1

Define Mitosis

Answer 1

Mitosis is defined as nuclear division giving rise to genetically identical cells

Question 2

What is Mitosis used for?

Answer 2

growth, repair of damaged tissues, replacement of cells and asexual reproduction

Question 3

How many copies of each chromosome do most body cells have

Answer 3

Most body cells have two copies

• We describe these cells as diploid

Question 4

When cells divide, what do their chromosomes do?

Answer 4

their chromosomes double beforehand (also known as duplication)

Question 5

What does cell division ensure

Answer 5

This ensures that when the cell splits in two, each new cell still has two copies of each chromosome (is still diploid)

Question 6

Just before mitosis, each chromosomes in the nucleus does what?

Answer 6

copies itself exactly (forms x-shaped chromosomes)

Question 7

Chromosomes line up along the centre of the cell where, what happens?

Answer 7

where cell fibers pull them apart

Question 8

All cells in the body (excluding gametes) are produced by, what?

Answer 8

by mitosis of the zygote

Question 9

What is Mitosis important for?

Answer 9

for replacing cells e.g, skin cells, red blood cells and for allowing growth (production of new cells e.g. when a zygote divides to form an embryo)

Question 10

Mitosis produces offspring that are, what?

Answer 10

that are genetically identical to the parent

Question 11

What is Meiosis

Answer 11

Meiosis is a type of nuclear division that gives rise to cells that are genetically different

Question 12

What is Meiosis used for?

Answer 12

It is used to produce the gametes (sex cells)

Question 13

When the gametes are formed, what must the chromosomes do?

Answer 13

The number of chromosomes must be halved

Question 14

If the chromosomes didn’t half, what would happen?

Answer 14

there would be double the number of chromosomes after they join at fertilisation in the zygote (fertilized egg)

Question 15

What is Meiosis described as?

Answer 15

a reduction division in which the chromosome number is halved from diploid to haploid, resulting in genetically different cells

Question 16

What are gametes described as?

Answer 16

as being haploid – having half the normal number of chromosomes

Question 17

Because of this double division, meiosis produces four, what?

Answer 17

haploid cells

Question 18

Describe the “First division”

Answer 18

chromosomes pair up along the centre of the cell, recombination occurs and then cell fibres will pull the pairs apart, each new cell will have one of each recombinant chromosome pair

Question 19

Describe the Second division

Answer 19

chromosomes will line up along the centre of the cell, cell fibres will pull them apart (as with mitosis)

Question 20

Exam Tip

Answer 20

Questions on cell division often ask for differences between mitosis and meiosis. Learn two or three and remember to BE SPECIFIC when giving your answer.

You should also know the reasons for a specific type of cell division taking place and the types of cells where each happen.