Unit 1 - Division and Differentiation Key Area 1

Question 1

What is a somatic cell?

Answer 1

A somatic cell is any cell in the body other than the cells involved in reproduction.

Question 2

What process produces more somatic cells?

Answer 2

Somatic stem cells divide by mitosis to form more somatic cells

Question 3

How many chromosomes are found in somatic cells?

Answer 3

Each somatic cell contains 46 chromosomes and is diploid (2 sets of 23chromosomes)

Question 4

What is a germline cell?

Answer 4

A germline cell is a gamete (sperm/egg) and the stem cells that divide to form gametes.

Question 5

5a) What process produces more germline cells?

b) What process produces gamete cells

Answer 5

a) Germline cells can divide by mitosis to produce more germline stem (diploid) cells
b) Germline cells can divide by meiosis to produce (haploid) gametes.

Question 6

What happens to germline cells during mitosis?

Answer 6

The nucleus of a germline stem cell can
divide by mitosis to maintain the diploid
chromosome number. Diploid cells have 23
pairs of homologous chromosomes.

Question 7

What happens to germline cells during meiosis?

Answer 7

The nucleus of a germline stem cell can
divide by meiosis. It undergoes two divisions,
firstly separating homologous chromosomes
and secondly separating chromatids. Haploid
gametes contain 23 single chromosomes.

Question 8

What is cellular differentiation?

Answer 8

Cellular differentiation is the process by
which a cell expresses certain genes to
produce proteins characteristic for that type
of cell. This allows a cell to carry out
specialised functions.

Question 9

What are Stem Cells?

Answer 9

Stem cells are cells that are unspecialised and have the ability to differentiate into specialised cells

Question 10

What are two features of Stem Cells?

Answer 10

They are different form other body cells because they can

Self renew (Make copies of themselves)  
AND  
Differentiate (Make other types of cells)

Question 11

What are the two different types of Stem Cells?

Answer 11

There are 2 different types of stem cells:-

1) Tissue Stem Cells (also called Adult Stem Cells)
2) Embryonic Stem Cells

Question 12

Where are embryonic stem cells found?

Answer 12

Embryonic Stem Cells are found in a human embryo.

Question 13

What feature of embryonic stem cells make them extremely useful and how are they able to do this?

Answer 13

These cells can differentiate into all the cell types that make up the individual, these cells are described as pluripotent.

They are able to do this because all of the genes in an Embryonic Stem Cell have the ability to be switched on

Question 14

What are tissue stem cells?

Answer 14

Tissue (adult) Stem Cells are involved in growth, repair and renewal of the cells found in that tissue.

Question 15

How do you describe tissue stem cells

Answer 15

They are described as being multipotent because they can differentiate into all of the cell types from the particular tissue they came from.

Question 16

Where do we find tissue stem cells?

Answer 16

Tissue stem cells found in bone marrow can give rise to red blood cells, platelets, phagocytes and lymphocytes.

Question 17

Why can tissue stem cells not differentiate into any cell type?

Answer 17

The reason that tissue stem cells cannot differentiate into any cell type is because some of the genes in a tissue stem cell have already been switched off which means they produce a limited range of cell types

Question 18

Explain the ethical debate surrounding the use of embryonic stem cells

Answer 18

For the stem cells from an embryo to be used this involves the destruction of the embryo.

Use of embryonic stem cells can offer effective treatments for disease and injury which can save lives
but
It involves the destruction of the embryo which destroys a potential life.

Question 19

What are therapeutic uses of stem cells?

Answer 19

can be used for repairing damaged or diseased organs or tissues e.g. corneal repair or regeneration of damaged skin for burns (skin graft)

Question 20

How are stem cells used in research

Answer 20

• Stem cells can be used as model cells to study how diseases develop or for drug testing
• Can provide information on how cell processes such as cell growth, differentiation and gene regulation work.
• Stem cells from the embryo can self-renew under the right conditions in the lab

Question 21

1. How do cancer cells divide?
2. What is a tumour?
3. How does a secondary tumour form

Answer 21

Cancer cells divide excessively because they do not respond to regulatory signals.

This results in a mass of abnormal cells called a tumour.

Cells within the tumour may fail to attach to each other , spreading through the body where they may form a secondary tumour.