Unit 1.1

Question 1

Somatic Cells

Answer 1

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

Question 2

Germline cells

Answer 2

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

Question 3

Somatic stem cells divide by

Answer 3

Somatic stem cells divide by mitosis to form more somatic cells.

Question 4

Germline stem cells divide by

Answer 4

Germline stem cells divide by mitosis and by meiosis.

Division by mitosis produces more germline stem cells.

Division by meiosis produces haploid gametes.

Question 5

(Germline) Mitosis

Answer 5

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 6

(Germline) meiosis

Answer 6

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 7

Cellular differentiation

Answer 7

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 8

Embryonic Stem cells

Answer 8

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 9

Tissue Stem Cells (adult)

Answer 9

Tissue stem cells are involved in the growth, repair and renewal of the cells found in that tissue. They are multipotent.

Tissue stem cells are multipotent as they can differentiate into all of the types of cell found in a particular tissue type. For example, blood stem cells located in bone marrow can give rise to red blood cells, platelets, phagocytes and lymphocytes.

Question 10

Therapeutic uses of SC

Answer 10

Therapeutic uses involve the repair of damaged or diseased organs or tissues.

The therapeutic uses of stem cells should be exemplified by how they are used in corneal repair and the regeneration of damaged skin.

Question 11

SC research basic

Answer 11

Research uses involve stem cells being used as model cells to study how diseases develop or being used for drug testing.

Question 12

SC research detail

Answer 12

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

Stem cell research provides information on how cell processes such as cell growth, differentiation and gene regulation work.

Question 13

The ethical issues of using embryonic stem cells.

Answer 13

Use of embryonic stem cells can offer effective treatments for disease and injury; however, it involves destruction of embryos.

Question 14

Cancer

Answer 14

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.