Cell division

Question 1

1.What is the role of Chromosomes in cells? 2.Where are they found?3.What do they contain ?4. how many chromosomes are there in a normal cell?

Answer 1

1)chromosomes carry genes which contain instructions for making new cells, tissues and organs.
2)each nucleus contains chromosomes.
3) Chromosomes carry hundreds to thousands of genes which are grouped together and many together can code for a particular characteristic.
4) We have 23 pairs of chromosomes in each cell- 46 in total. One chromosome from the mother and one from the father in each pair.

Question 2

Describe the 3 stages of the cell cycles.
1- 7
2-2
3-2

Answer 2

Cell cycle occurs in 3 stages.
1) cells grow bigger, increase in mass and subcellular structures (mitochondria, ribosomes, chloroplasts) and replicate DNA ready for cell division.
2)Cell cycle involves cell division in a process called mitosis-one set of chromosomes is pulled to each end of the dividing cell and the nucleus divides.
3)cytoplasm and cell membrane divide to form 2 identical daughter cells.

Question 3

Describe how mitosis occurs?

Answer 3

one set of chromosomes is pulled to each end of the dividing cell and the nucleus divides.
cytoplasm and cell membrane divide to form 2 identical daughter cells.

Question 4

how does differentiation occur in plants? (2)
Is differentiation permanent in plant cells- describe?

Answer 4

1)Undifferentiated cells are formed at active regions of stem and roots called meristems.
2)Mitosis occurs at meristem where plant cells elongate and grow before differentiating when they reach their final position in the plant.

Differentiation is not permanent in plant cells and when a plant cell is repositioned- it can redifferentiate.

Question 5

How does cell differentiation occur in animals?

Answer 5

some genes have been switched on and some off resulting in different types of specialised cells which have different sub cellular structures to carry out specific functions- nerve, muscle skin cells.

Question 6

define cloning
describe the production of plant clones.

Answer 6

cloning- production of identical offspring.
1) requires a tiny piece of leaf which will in the right conditions become unspecialised and undergo mitosis to produce more undifferentiated cells which will also undergo mitosis.
2) given different conditions- the cells will differentiate to form xylem, phloem, photosynthetic and root tissues resulting in a new identical tiny plant which can be grown.

Question 7

how are stem cells different from other body cells?

Question 8

describe the function of stem cells in embryos.

Question 9

describe the function of stem cells in adult animals.

Question 10

describe the function of stem cells in plants.

Question 11

how are stem cells used for treatment in medicine?

Question 12

describe the process of therapeutic cloning.

Question 13

describe the benefits, risks, social and ethical issues of using stem cells in research and treatment.

Question 14

Why might new cells be needed in the body?

Answer 14

for growth and repair

Question 15

what are genes?

Answer 15

sections of DNA.
carry information to control a particular characteristic of the body.

Question 16

How many chromosomes do sex cells have and from who?

Answer 16

23 chromosomes all from the parent.

Question 17

Define mitosis

Answer 17

Cell division resulting in 2 genetically identical cells.

Question 18

T/F all the body’s cells have the same chromosomes.

Answer 18

True

Question 19

What type of cell division occurs in asexual reproduction? Is there genetic variation in this type of reproduction?

Answer 19

Mitosis- no genetic variation.

Question 20

define growth.

Answer 20

the permanent increase in size as a result of cell enlargement and cell division.

Question 21

Even though all cells of the body have the same chromosomes- why are they not the same?

Answer 21

Cells undergo differentiation as they divide, grow and develop.

Question 22

What is a stem cell and Where are they normally found?

Answer 22

unspecialised cell- can become any type of cell.
Normally found in the early development of animal and plant cells.

Question 23

Do blood and skin cells divide- if not then what happens?

Answer 23

No- adult stem cells replace dead and damaged skin and blood cells.

Question 24

Do nerve cells divide once they have differentiated- if so what happens to them?

Answer 24

No and they can so cannot be replaced by adult stem cells so they are irreplaceable after damage.

Question 25

T/F In mature animals no growth takes place but repair and replacement mainly.

Answer 25

True

Question 26

why is it hard to clone animal cells?

Answer 26

Because they permanently differentiate in embryonic development so animals clones can only be made by cloning the embryo in some way or if adult cells are used to make an embryo.