B2 Cell Divison

Question 1

explain why chromosomes in

body cells are normally found in pairs

Answer 1

One chromosome is inherited from the mother and one is inherited from the father. The chromosomes in each pair carry the same gene in the same location.

Question 2

How many pairs of chromosomes are found in human body cells?

Answer 2

In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46.

Question 3

What is Mitosis

Answer 3

a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus.

Question 4

describe situations where mitosis

is occurring.

Answer 4

Mitosis takes place in all parts of your body, keeping your tissues and organs in good working order. Healing is an example of mitosis, growing is an example of mitosis, even cancer is an example of mitosis.

Question 5

What is the first stage of Cell Cycle?

Answer 5

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

Question 6

What is the second stage of Cell cycle?

Answer 6

Mitosis is a part of the cell cycle when replicated chromosome are separated into two nuclei.

Question 7

why is the second stage important?

Answer 7

it plays an important part in the development of embryos and its important for the growth and development of our bodies

Question 8

Why is Mitosis important in the Second Stage?

Answer 8

In this process one set of chromosomes is pulled to each of the dividing cell and the nucleus divides.

Question 9

What is the Third Stage of the Cell cycle?

Answer 9

The stage during which the cytoplasm and the cell membranes also divde to form two identical daughter cells.

Question 10

What are chromosomes?

Answer 10

The structure made of DNA that codes for all the characteristics of an organism.

Question 11

What is a gene?

Answer 11

The basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell’s chemistry - particularly protein production.

Question 12

What are gametes?

Answer 12

Sex cells are also known as gametes. Male gametes are made by male reproductive structures. Female gametes are made by female reproductive structures. A gamete contains a single set of chromosomes in its nucleus

Question 13

What is Differentiation?

Answer 13

Cells that become speciallised to carry out particular jobs , they carry out particular functions and have particular sub-cellular structures.

Question 14

describe the importance of cell
differentiation in multicellular
organisms.

Answer 14

Once a cell becomes differentiated it only expresses the genes that produce the proteins characteristic for that type of cell. Differentiated cells are important in a multicellular organism because they are able to perform a specialised function in the body.

Question 15

state why plant clones are genetically

identical to each other

Answer 15

Cells from meristems can be cloned. These cells can be removed from a plant and grown in tissue culture. The cells are grown in a culture medium that contains agar – to provide support and water for the growing cells – along with nutrients and plant hormones to stimulate growth and cell division.

Question 16

explain how using tissue culture

creates a clone of a plant

Answer 16

also called micropropagation. It works with small pieces of plants, called explants. These are grown in vitro using sterile agar jelly that contains plant hormones and nutrients. This makes tissue culture more expensive and difficult to do than taking cuttings.

Question 17

What is the process from Fertillised egg to Early Embyro

Answer 17

Mitosis

Question 18

What is the process from Early Embryo to Late Embyro

Answer 18

Mitosis + Stem Cells

Question 19

What are Stem cells?

Answer 19

Stem cells is a single cell that can replicate itself or differentiate into many cell types.

Question 20

Where can Stem cells be found apart from the Embryo

Answer 20

Stem Cells can be also found in developed organisms as “Adult” stem cell

Question 21

Are Adult Stem Cells easy to use?

Answer 21

Adult Stem Cells are more limited ( they can’t become any all type , only certain cell types)

Question 22

Are Adult Stem Cells easy to find?

Answer 22

Adult Stem Cells are harder to ‘isolate’ / only found in small numbers.

Question 23

What is the process from Late Embryo to Foetus

Answer 23

Mitosis + Differentiation

Question 24

describe differences between

embryonic and adult stem cells.

Answer 24

Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin.

Question 25

list some arguments for and against

the use of stem cells.

Answer 25

Stem cells have great potential for:

• treating patients with currently untreatable conditions
• growing organs for transplants
• medical research

Ethical issues

• A source of embryonic stem cell is unused embryos produced by in vitro fertilisation.
• For therapeutic cloning, is it right to create embryos for therapy, and destroy them in the process?
• Embryos could come to be viewed as a commodity, and not as an embryo that could develop into a person.