1.1 - Division & Differentiation In Human Cells

Question 1

Somatic cells definition

Answer 1

Somatic cells are any cells in the body other than the cells involved in reproduction.

Question 2

What cells make up an organism?

Answer 2

Somatic cells are the cells that make up an organism
- e.g. organs, muscle, fat, bone, skin cells

Although somatic cells differ greatly in their form and function, within a single organism they all contain exactly the same DNA.

Question 3

Somatic cells - division

Answer 3

Somatic cells divide by MITOSIS to form more somatic cells which maintains the diploid chromosome number.

Diploid cells have 23 pairs of homologous chromosomes.

Question 4

Why is mitosis important?

Answer 4

• growth
• repair
• maintain the chromosome complement

Question 5

Germline cells definition

Answer 5

Germline cells include the gametes and the stem cells that divide to produce the gametes.

(Sperm and ova)

Question 6

Division of germline cells (mitosis)

Answer 6

The nucleus of a germline stem cell can divide by mitosis to produce more germline cells.

These cells maintain the diploid chromosome number.

Question 7

Division of germline cells (meiosis)

Answer 7

The nucleus of a germline stem cell can divide by MEIOSIS to produce HAPLOID gametes.

It undergoes two divisions:

• separating homologous chromosomes
• separating chromatids

Haploid gametes contain 23 single chromosomes.

Question 8

Cellular differentiation definition

Answer 8

Cellular differentiation is the process by which a cell becomes specialised.

The cell expresses certain genes to produce proteins characteristic for that type of cell which allows the cell to carry out specialised functions.

Question 9

Stem cells definition

Answer 9

Stem cells are unspecialised somatic cells that have the ability to differentiate into a diverse range of specialised cells.

Question 10

What are the types of stem cell?

Answer 10

Embryonic

Tissue

Question 11

Embryonic stem cells

Answer 11

Cells in the very early embryo can differentiate into all the cell types that make up the individual and so are PLURIPOTENT.

All the genes in embryonic stem cells can be switched on so these cells can differentiate into any type of cell.

Question 12

Tissue stem cells

Answer 12

Tissue stem cells can differentiate into all of the types of cell found in a particular tissue type and are said to be MULTIPOTENT.

E.g. blood stem cells located in bone marrow can give rise to red blood cells, platelets, phagocytes and lymphocytes.

Question 13

Stem cells - research

Answer 13

Research involves stem cells being used as model cells.

• how cell processes such as cell growth, differentiation and gene regulation work.
• the study of diseases and their development
• drug testing

Question 14

Stem cells - therapeutic uses

Answer 14

• treatment of diseases - e.g. heart disease, leukemia
• regeneration of damaged skin for burns patient
• cornea repair

Question 15

How are stem cells used outside the body?

Answer 15

Stem cells from the embryo can self-renew, under the right conditions, in the lab.

Question 16

Ethical issues surrounding the of stem cells - FOR

Answer 16

Embryonic stem cells have the potential to discover cures for diseases and can be used in the treatment of injury.

Question 17

Ethical issues surrounding the of stem cells - AGAINST

Answer 17

Destruction of an embryo which could be a potential life.

Question 18

Cancer cells

Answer 18

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 secondary tumours.

Question 19

Somatic cells differences and similarities

Answer 19

Although somatic cells differ greatly in their form and function, within a single organism they all contain exactly the same DNA.