Cell division

Question 1

What is the purpose of the chromosome?

Answer 1

Carry the genes that contain the instruction for both making new cells and all the tissues and organs needed to make an entire new you.

Question 2

What is DNA?

Answer 2

a unique molecule that makes up your chromosomes.

Question 3

How many chromosomes are there in a human cell?

Answer 3

46 chromosomes in the nucleus of body cells. They are arranged in 23 pairs. In each pair of chromosomes is inherited from each parent. Sex cells only have one chromosome from each pair so only 23 chromosomes in total.

Question 4

What is the cell clycle?

Answer 4

Body cells that divide in a series of stages known as the cell cycle.

Question 5

What is mitosis?

Answer 5

Produces two identical cells allowing the body to have all the same chromosomes so they have the same genetic information. Mitosis produces all the additional cells needed for growth and development in multicellular organisms.

Question 6

Why is there little or no genetic variation in asexual reproduction?

Answer 6

The cells of the offspring are produced by mitosis from the cells of their parents.

Question 7

What happens in each stage of making of a new cell?

Answer 7

1. Stage 1: Cell replicates their DNA to form 2 copies of each chromosome ready for cell division. They also increase the number of sub-cellular structures such as mitochondria, ribosomes and chloroplasts.
2. Stage 2: mitosis: one set of chromosomes is pulled to each end of the dividing cell and the the nucleus divides.
3. Stage 3: Cytoplasm and the cell membranes divide to form two identical daughter cells.

Question 8

Why aren’t all of the cells in our body the same?

Answer 8

They are not the same as the original cell because they divide, grow and develop, they also begin to differentiate.

Question 9

What is a stem cell?

Answer 9

In the early development of animals and plant embryos, the cells are unspecialized and they can become any type of cell that is needed.

Question 10

What is differentiation?

Answer 10

Some of the cells genes have been switched on and off causing different type of specialized cells become different shapes or sizes and contain sub-cellular structures to carry out specific functions.

Question 11

How are specialized cells produced?

Answer 11

1. Mitosis forming the same type of cell, e.g muscle cells.
2. Some differentiated cells so adult stem cells replace dead or damaged cells.
3. Some specialized cells do not divide or are replaced for example nerve cells.

Question 12

How are plant cells able to differentiate all throughout their lives?

Answer 12

Undifferentiated cells are formed at active regions of the stems and roots known as meristems. In these areas, mitosis takes place almost continuously. The cells then get longer and bigger before they finally differentiate.

Question 13

How is differentiation not permanent in a plant cell?

Answer 13

You can move a plant cell from one part of a plant to another. There it can re-differentiate and become a completely different type of cell.

Question 14

What is cloning in plants?

Answer 14

Producing identical offspring.

Question 15

How does cloning plants work?

Answer 15

In the right conditions a plant cell will become unspecialized and undergo mitosis many times. Each of these undifferentiated cells will produce more cells by mitosis. Given different conditions, these cells will differentiate to form tissues that are needed to form a tiny new plant identical to the parent.

Question 16

Why is it difficult to clone animals?

Answer 16

Most animal cells differentiate permanently early in the embryo development. The cells cannot change back. As a result, artificial animal clones can only be made by cloning embryos.

Question 17

How are embryonic stem cells created?

Answer 17

An egg and sperm cell fuse to form a single new cell. That cell divides and becomes a hollow ball of cells - the embryo. The inner cells of this ball are the embryonic stem cells.

Question 18

What is the use of stem cells in plants?

Answer 18

1. Produces large numbers of rare plants reliably and safely. This may help us same some rare plants from extinction.
2. Produce large populations of identical plants for research. This is important as scientists can change variables and observe the effects on genetically identical individuals.

Question 19

What are the risks of using stem cells?

Answer 19

1. A risk that adult stem cells might be infected with viruses, and so could transfer the infections to patients.
2. If stem cells from an adult are used to treat an unrelated person they may trigger an immune response. The patient may need to take immunosuppressant drugs to stop their body from rejecting new cells.

Question 20

What are the ethical issues of using stem cells?

Answer 20

Embryonic stem cells came from aborted embryos. Some people question the use of a potential human being as a source of cells to cure others.

Question 21

What examples of potential therapies are going to be used using stem cells?

Answer 21

1. Spinal cord injuries
2. Type 1 diabetes
3. The heart after damage in a heart attack
4. Eyesight in people with limited or no vision
5. Damaged bone and cartilage