Cell Division

Question 1

What is a chromosome ?

Answer 1

The nucleus of a cell contains chromosomes made of DNA. Each chromosome carries hundreds of thousands of genes

Question 2

Facts about genes ?

Answer 2

Different genes contain the code to make different proteins and so control the development of different characteristics.

Question 3

Why are chromosomes found in pairs ?

Answer 3

One chromosome from each parent

Question 4

Do all species have the same number of chromosomes ?

Answer 4

No. Different species have different number of pairs of chromosomes, e.g. humans have 23 pairs and dogs have 39 pairs

Question 5

What is meant by cell cycle ?

Answer 5

Cells go through a series of changes involving growth and division, called the cell cycle

Question 6

What are the stages of mitosis ?

Answer 6

1. Parent cell with two pairs of chromosomes
2. Each chromosome replicates itself
3. Chromosomes line up along the centre of the cell, divide and copies move to opposite poles
4. Each daughter cell has the same number of chromosomes, and contains the small genes, as the parent cell

Question 7

Why is cell division by mitosis important ?

Answer 7

It is important because it makes new cells for :
1.Growth and development of multicellular organisms
2.Repairing damaged tissues
3.asexual reproduction

Question 8

What are stem cells ?

Answer 8

Some cells are undifferentiated- they do not yet become specialised.
This means that they can divide to make different types of cells. These are called stem cells

Question 9

Where are stem cells found ?

Answer 9

In human embryos, in the umbilical cord of a new born baby, and in some organs and tissues

Question 10

What are stem cells from human embryos called ?

Answer 10

Embryonic stem cells and can make all types of cells

Question 11

What are adult stem cells and where can they be found ?

Answer 11

Adult stem cells are found in some organs and tissues, e.g. bone marrow. They can only make certain types of cells and their capacity to divide is limited

Question 12

What are the uses of stem cells and how are they useful ?

Answer 12

Stem cells may be very useful in treating conditions where cells are damaged or not working properly, such as diabetes and paralysis. They could be used to replace damaged cells

Question 13

What is meant by therapeutic cloning ?

Answer 13

Involves creating embryonic stem cells from an adult

Question 14

Describe the steps of therapeutic cloning ?

Answer 14

1.A nucleus from the patient is added to an egg that has had its nucleus removed
2. The egg is stimulated to divide, becoming an embryo.
3. The embryo is a clone of the patient with the same genes.
4. The stem cells in the embryo will not be rejected by the patient and could help treat the patients condition

Question 15

What are the benefits, risks and social and ethical issues of embryonic stem cells ?

Answer 15

Benefits include saving life and reducing suffering, however, risk of transfer of viral infection and some people may object due to religious and ethical reasons

Question 16

Where are stem cells found in plants ?

Answer 16

Stem cells are found in special areas in a plant called meristems

Question 17

What do meristems allow and what can they be used for ?

Answer 17

These meristems allow plant to make new cells for growth
The stem cells can also be used to produce clones of plants quickly. This could be useful for a number of reasons :
1.Rare species could be cloned to protect them from extinction
2. Large number of identical crop plants with special features, such as disease resistance, can be made