B2- Cell Division And Differentiation

Question 1

What is a chromosome?

Answer 1

A long thin thread of DNA

Question 2

How many chromosome do humans have?

Answer 2

23 pairs (46 in total)

Question 3

What is a gene? What does it do?

Answer 3

A section of DNA In a chromosome

- it controls characteristics

Question 4

What are the 4 Base pairs?

Answer 4

A-T

C-G

Question 5

What are gametes?

Answer 5

sex cells and only contain 23 chromosomes, e.g sperm and egg cells which combine together and share their chromosomes

Question 6

Name and describe stage 1 of cell division

Answer 6

Interphase, this is the longest part

• sub cellular structures increase
• cell replicates it DNA to form 2 copies of each chromosome
• grows bigger + increase in mass

Question 7

Name and describe stage 2 of cell division

Answer 7

Mitosis

- in this process one set of chromosomes is pulled to each end of the cell and the nucleus divides

Question 8

Describe stage 3 of cell division

Answer 8

Cytoplasm and the cell membrane divide to form 2 identical daughter cells

Question 9

Where are stem cells found in an animal?(2)

Answer 9

• early human embryos

- adult bone marrow

Question 10

Name 2 ways in which stem cells can be used to fix problems in the human body

Answer 10

• be transferred to replace faulty cells i sick people
• injected into spine of paralysed people to make more nerve cells
• make insulin producing cells for people with diabetes

Question 11

Name 2 reasons why someone will be against the use of stem cells

Answer 11

• by using embryos you are ending a potential life (or from a religious point of view killing actual life)
• you could potentially clone people if you splint the embryo in 2

Question 12

What do scientist say in argument to the issues raised by the use of stem cells? (Apart from the fact that they can help people)

Answer 12

• more embryos die than live so it just better that they are used
• to prevent cloning some some scientist have began taking stem cells from a much earlier stage, blastocyst, which doesn’t allow cloning

Question 13

Whats so special about stem cells?

Answer 13

They are undifferentiated so can develop into any specialist cell

Question 14

Differentiation

Answer 14

When cells transform into specialist cells that perform a particular job and have particular sub cellular structures structures for this

Question 15

How is differentiation different in plant cells?

Answer 15

Once cells specialise (differentiate)they can re-differentiate into other specialised cells. So if you took a rose’s leave and plant it in the right conditions you would grow a rose plant

Question 16

Where are stem cells found in a plant?

Answer 16

Everywhere

Question 17

Why is the ability of body cells to divide important?

Answer 17

for growth / repair / replacement