B2 Cell division

Question 1

What does the nucleus contain?

Answer 1

genetic material in the form of chromasomes

Question 2

What is the cell cycle?

Answer 2

When body cells divide to produce new cells

Question 3

What do chromosomes contain?

Answer 3

genes to control the development of different characteristics

Question 4

What are chromosomes?

Answer 4

coiled up lengths of DNA molecules

Question 5

How many chromosomes do humans have?

Answer 5

23 PAIRS (46 single)

(one from the mother and one from the father)

Question 6

what is mitosis?

Answer 6

where a cell reproduces by splitting in to two identical cells

Question 7

What is mitosis used for in multicellular organisms?

Answer 7

to grow and replace damaged cells

Question 8

what are the stages of the cell cycle?

Answer 8

1. Number of subcellular structures increases. Chromosomes duplicate
2. chromosomes line up and cell fibres pull the two arms of the chromosomes to opposite ends. Membranes form around the chromosomes which become nuclei
   
   1. cytoplasm and membranes divide. two daughter cells are produced

Question 9

What is differentiation?

Answer 9

the process where a cell changes to become specialised for it’s job

Question 10

What does differentiation allow cells to do?

Answer 10

to carry out specific functions as they have different subcellular structures

Question 11

when does most differentiation occur?

Answer 11

as an organism develops

• in animal cells, the ability to differentiate is lost early
• plant cells do not lose the ability

Question 12

What are the cells that differentiate in mature animals used for?

Answer 12

repairing and replacing cells

Question 13

what are stem cells?

Answer 13

undifferentiated cells

Question 14

where do stem cells come from?

Answer 14

• early human embryos
• adult bone marrow

Question 15

What can embryonic stem cells do that adult stem cells can’t?

Answer 15

embryonic stem cells can differentiate into any cell

Question 16

what are adult stem cells already used for?

Answer 16

to cure diseases

eg. replacing faulty blood cells

Question 17

what can embryonic stem cells be used for?

Answer 17

to replace faulty cells

eg. insulin producing cells, nerve cells

Question 18

what is therapeutic cloning?

Answer 18

where an embryo is made to have the same genetic information as the patient.

this means the stem cells would not be rejected by the patient

Question 19

What are the risks of stem cells?

Answer 19

They could be infected with viruses and this could transfer to the patient.

adult stem cells could be rejected by the patient.

Question 20

how do bacterial cells divide?

Answer 20

simple cell division where 1 cell splits into 2 bacterial cells. this is known as binary fission.

Question 21

what is the formula to calculate the number of bacteria?

Answer 21

number of bacteria = 2^{n (number of rounds of division)}

Question 22

name some aseptic techniques:

Answer 22

sterilising by passing the aperatus through a flame

sealing the petri dish with tape to stop unwanted microorganisms contaminating

clean surfaces with disinfectant

Question 23

why are bacteria grown at 25 degrees in school labs?

Answer 23

to reduce the chance of harmful bacteria growing

Question 24

why are the petri dishes stored upside down?

Answer 24

to prevent condensation dripping into the samples

Question 25

how can you measure the efficacy of an antibiotic on an agar plate?

Answer 25

calculate the area of the zone of inhibition (where bacteria have not grown)

Question 26

where are stem cells found in plants?

Answer 26

in meristem tissue

Question 27

when can stem cells in plants differentiate?

Answer 27

at any point in the life of the plant

Question 28

what are the uses of plant stem cells?

Answer 28

a rare plant can be cloned to stop it going extinct

crop plants can be cloned