Division and Differentiation in Human Cells

Question 1

What is a somatic cell?

Answer 1

Any cell in the body other than cells involved in reproduction.

Question 2

What are somatic cells produced from?

Answer 2

They have differentiated from somatic stem cells to have specific functions and are grouped to form different types of tissue.

Question 3

How do somatic cells divide?

Answer 3

By mitosis only.

Question 4

Somatic cells are diploid cells. What is a diploid cell?

Answer 4

A cell with 2 pairs of homologous chromosomes.

Question 5

Why is it important to maintain chromosome complement by mitosis?

Answer 5

So that no genetic information is lost and each daughter cell contains all the characteristics of its species.

Question 6

What are germline cells?

Answer 6

Gametes (sperm and ova) and the stem cells that divide to form gametes.

Question 7

How do germline stem cells divide?

Answer 7

The nuclei of germline stem cells By mitosis to produce more germline stem cells.

By meiosis to produce haploid gametes.

Question 8

Describe the process of meiosis in a germline cell.

Answer 8

The nucleus of a germline cell undergoes two divisions

• Separation of homologous chromosomes
• Separation of chromatids.

Question 9

How many chromosomes are in a haploid cell?

Answer 9

23

Question 10

How many chromosomes are in a diploid cell?

Answer 10

46

Question 11

Define the process of cellular differentiation.

Answer 11

The process by which a cell expresses certain genes to produce proteins that are characteristic for that type of cell.

Question 12

What does cellular differentiation allow a cell to carry out?

Answer 12

This allows a cell to carry out specialised functions. These differentiated, specialised cells make up the tissues in the body.

Question 13

Differentiated cells lose the ability to make copies of themselves. So what must multicellular organisms do to replenish cells when needed?

Answer 13

Retain some unspecialised cells called stem cells.

Question 14

What are the two types of stem cell?

Answer 14

Embryonic and tissue

Question 15

Where are embryonic stem cells extracted?

Answer 15

A blastocyst

Question 16

Why are embryonic stem cells the most useful type of stem cell?

Answer 16

All of its genes can be switched on, meaning that embryonic stem cells can differentiate into any type of cell. This is called pluripotent.

Question 17

What are tissue stem cells involved in?

Answer 17

Growth and repair of tissue.
Renewal of cells found in the tissue.

Question 18

What can tissue stem cells differentiate into?

Answer 18

All types of cell found in a particular tissue type. This is called multipotent.

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

Question 19

What do therapeutic uses of stem cells involve?

Answer 19

Repair of damaged organs or tissue.

Question 20

Give examples of therapeutic uses of stem cells.

Answer 20

Corneal repair
Regeneration of damaged skin

Question 21

How can stem cells be used in research?

Answer 21

They can be used as model cells to study how diseases develop.

Used for drug testing

Provides info on cellular processes such as cell growth, differentiation and gene regulation work.

Question 22

What ethical issue arises from use of embryonic stem cells?

Answer 22

Destruction of embryos.

Question 23

What is the cutoff time by which embryos are either used or destroyed in research and why?

Answer 23

14 days because at this point the nervous system begins to develop.

Question 24

What is a tumour?

Answer 24

A mass of abnormal cells.

Question 25

What causes a tumour to form?

Answer 25

**Cancer cells divide exponentially** as they **don’t respond to regulatory signals**.

Question 26

How do secondary tumours occur?

Answer 26

When **cells within the tumour fail to attach to each other**, they spread through the body,

Question 27

What can embryonic stem cells do under the right conditions in the lab?

Answer 27

Self renew.