B2 Cell division

Question 1

What happens before a cell divides?

Answer 1

It makes a copy of every chromosome’s DNA

Question 2

What happens to the nuclear membrane?

Answer 2

It breaks down

Question 3

What happens to the chromosomes during mitosis?

Answer 3

• They join up in the centre of the cell
• They then separate to opposite sides of the cell
• New nuclear membranes form and the cell begins to divide

Question 4

What is special about the two cells produced during mitosis?

Answer 4

They are genetically identical

Question 5

What is a gene?

Answer 5

A short section of DNA that codes for a protein/controls a characteristic

Question 6

What are chromosomes?

Answer 6

Thread-like structures in the nucleus that carry genes

Question 7

What is DNA?

Answer 7

Deoxyribonucleic acid, the material of inheritance

Question 8

What is mitosis?

Answer 8

Cell division that produces two genetically identical daughter cells

Question 9

How many pairs of chromosomes are there in most human cells?

Answer 9

23

Question 10

Why is mitosis important?

Answer 10

• Needed to produce cells that are needed for organisms to grow
• Needed to replace cells that have become worn out and repair damaged tissue
• Asexual reproduction

Question 11

How many chromosomes are in one human body cell?

Answer 11

46

Question 12

What is a stem cell?

Answer 12

Undifferentiated cell with the potential to become specialised

Question 13

What are adult stem cells?

Answer 13

Stem cells that can only differentiate into a specific type of cell

Question 14

Describe stage one of the cell cycle

Answer 14

Replication of DNA to form two copies of each chromosome and synthesis of new sub-cellular structures

Question 15

Describe stage two of the cell cycle

Answer 15

Mitosis: one set of chromosomes is pulled to each end of the dividing cell and the nucleus divides

Question 16

Describe stage three of the cell cycle

Answer 16

The cytoplasm and the cell membranes also divide to form two genetically identical daughter cells

Question 17

Where does differentiation occur in plants?

Answer 17

Meristems found in the shoot and root tips

Question 18

Define cloning

Answer 18

Production of identical offspring by asexual reproduction/mitosis

Question 19

How does cell differentiation varies in animals and plants?

Answer 19

• Many types of plant cells retain the ability to differentiate throughout life
• Most types of animal cell differentiate at an early stage of development

Question 20

What are embryonic stem cells?

Answer 20

Stem cells from an early embryo that can differentiate into all cell types

Question 21

Diseases that may be treated with stem cell treatment

Answer 21

• Paralysis
• Diabetes
• Blindness

Question 22

How can we use stem cells to treat someone with type 1 diabetes?

Answer 22

Induce embryonic stem cells to produce healthy pancreas cells to make enough insulin

Question 23

Why is the ability to clone plants quickly a benefit?

Answer 23

Produce large numbers of rare plants reliably and safely to stop their extinction and for research, agriculture advances

Question 24

Problems with embryonic stem cells

Answer 24

• Some people feel that, as the embryo cannot giver permission, using it is a violation of its human rights
• Progress in developing therapies using embryonic stem cells has been relatively slow, difficult, expensive, and hard to control
• It is proving difficult to persuade embryonic stem cells to differentiate into the type of cells needed to treat patients
• Embryonic stem cells divide and grow rapidly, so they might cause cancer if they are used to treat people

Question 25

Problems with adult stem cells

Answer 25

- There is a risk that adult stem cells might be infected with viruses, and so could transfer the infections to patients - If stem cells from an adult are used to treat another unrelated person, they may trigger an immune response. The patient may need to take immunosuppressant drugs to stop their body rejecting their new cells - adult stem cells can only differentiate into specific types of cells so there are a limited number of diseases that they can be used to treat

Question 26

Therapeutic cloning

Answer 26

A cloned early embryo is produced, using cells from an adult, with the same genes as the patient so the stem cells produced are not rejected and may be used for medical treatment

Question 27

Zygote

Answer 27

The single new cell formed right after fusion of gametes

Question 28

Where do you get adult stem cells in animals?

Answer 28

Bone marrow

Question 29

What is binary fission?

Answer 29

A type of cell division process by which prokaryotic organisms, like bacteria, divide and reproduce

Question 30

what is differentiation?

Answer 30

the process where cells become specialised for a particular function

Question 31

why is differentiation important in living organisms?

Answer 31

- all cells in an early animal or plant embryo are unspecialised - differentiation fulfils organisms' requirements for different cells to carry out different roles e.g. muscle cells, blood cells etc

Question 32

explain how a transplant of bone marrow cells can help to treat medical conditions

Answer 32

- bone marrow cells are unspecialised and can differentiate into many different types of cells - so will cure diseases where new cells are needed

Question 33

what is one section of genetic material on a chromosome called?

Answer 33

gene

Question 34

what are the similarities between prokaryotic and eukaryotic cells?

Answer 34

- both have a cytoplasm - both contain DNA - both have a cell membrane - both have ribosomes

Question 35

what are the differences between prokaryotic and eukaryotic cells?

Answer 35

- eukaryotic cells have a nucleus, prokaryotic cells do not - prokaryotic cells are smaller than eukaryotic cells - eukaryotic cells contain mitochondria, prokaryotic cells do not - prokaryotic cells have plasmids, eukaryotic cells do not

Question 36

name the cell division that produces genetically identical body cells for growth and repair

Answer 36

mitosis

Question 37

describe three differences between the processes of mitosis and meiosis

Answer 37

- cells divide once during mitosis, but twice during meiosis - meiosis produces four cells but mitosis produces two cells - mitosis produces cells with two of each chromosome, meiosis produces cells with one of each chromosome

Question 38

describe one similarity between the processes of mitosis and meiosis

Answer 38

- increase in the number of sub-cellular structures - DNA replicates

Question 39

why is mitosis important in living organisms?

Answer 39

to repair tissues