B3 cell division

Question 1

What is a stem cell?

Answer 1

undifferentiated cell that can differentiate into one or more specialised cell type

Question 2

What are adult stem cells?

Answer 2

Stem cells from adults that can only differentiate into certain specialised cells

Question 3

Where can adult stem cells be found?

Answer 3

bone marrow

Question 4

What are embryonic stem cells?

Answer 4

Stem cells from embryos that can differentiate into any specialised cell

Question 5

Where are embryonic stem cells found?

Answer 5

early human embryos (usually spare embryos from fertility clinics)

Question 6

What is therapeutic cloning?

Answer 6

Patient’s stem cells are used to create an early embryo clone of themselves - stem cells from the embryo can then be used to treat the patient’s medical conditions

Question 7

Give one advantage of using therapeutic cloning

Answer 7

Stem cells from embryo are not rejected when transplanted as they have the same genes as the patient

Question 8

Give one advantage of using adult stem cells

Answer 8

Fewer ethical issues as obtained from adults who can consent to their use

Question 9

Give two disadvantages of using adult stem cells

Answer 9

1. Can take a long time for a suitable donor to be found;
2. Can only differentiate into some specialised cell types, so can treat fewer diseases.

Question 10

Give two advantages of embryonic stem cells

Answer 10

1. can differentiate into any specialised cell, can be used to treat many diseases
2. Easier to obtain as they are found in spare embryos from fertility clinics

Question 11

Give two disadvantages of using embryonic stem cells

Answer 11

1. ethical issues surrounding their use, as every embryo is a potential life
2. potential risks involved with treatments, such as the transfer of viral infections

Question 12

What are plant meristems?

Answer 12

Area where rapid cell division occurs in the tips of toots and shoots

Question 13

Give two advantages of using plant meristems to clone plants

Answer 13

1. Rare species can be cloned to protect them from extinction;
2. Plants with special features (e.g. disease resistance) can be cloned to produce many copies

Question 14

Give one disadvantage of using plant meristems to clone plants.

Answer 14

No genetic variation, so, for example, an entire cloned crop could be destroyed by a disease

Question 15

What is cell division by mitosis?

Answer 15

body cells divide to form two identical daughter cells

Question 16

What is the purpose of mitosis?

Answer 16

growth and repair of cells
asexual reproduction

Question 17

What happens during the first stage of the cell cycle?

Answer 17

cell grows bigger;
chromosomes duplicate;
number of subcellular structures (e.g. ribosomes and mitochondria) increases

Question 18

What happens during mitosis?

Answer 18

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

Question 19

What happens during the third stage of the cell cycle?

Answer 19

the cytoplasm and cell membrane divide, forming two identical daughter cells

Question 20

What does cell ‘differentiation’ mean?

Answer 20

The process by which a cell changes to become specialised for its job

Question 21

How do prokaryotes divide?

Answer 21

Binary fission

Question 22

Describe binary fission

Answer 22

1. Circular DNA replicates
2. Cell gets bigger and the circular DNA moves to opposite poles
3. Cytoplasm begins to divide and new cell walls begin to form
4. The cytoplasm divides and two daughter cells are produced.

Question 23

What is formed at the end of binary fission

Answer 23

two daughter cells, each with an exact copy of the circular DNA but different numbers of plasmids