Key area 1- Division & Differentiation in Human cells

Question 1

Describe a somatic cell

Answer 1

. It is any cell in the body other than cells involved in reproduction (gametes)
. They divide by mitosis to form more somatic cells
. They each contain 46 chromosomes, and are diploid (two homologous sets of 23 chromosomes)

Question 2

Describe a germline cell

Answer 2

. They are gametes (sperm & ova), as well as the stem cells which divide to form gametes.
.They can divide by mitosis to produce germline stem cells, to maintain the diploid chromosome number
. They can also divide by meiosis to produce haploid gametes, it undergoes two divisions. Firstly, separating homologous chromosomes and secondly separating chromatids.

Question 3

What is cellular differentiation?

Answer 3

. The process by which a cell expresses certain genes to produce proteins characteristic for that type of cell.
.Simply, an unspecialised cell becomes specialised to carry out a specific function

Question 4

What does cellular differentiation allow for?

Answer 4

. It allows for a cell to carry out specialised functions .such as a basic animal cell becoming specialised into a goblet cell in the trachea

Question 5

What are some examples of differentiated cells?

Answer 5

.Sperm cells
.Goblet cells
.Nerve cell
.Red blood cells

Question 6

What are Stem cells?

Answer 6

.Cells that are unspecialised and have the potential to differentiate into specialised cells
.There are two different types: embryonic stem cells and tissue stem cells

Question 7

What is an embryonic stem cell?

Answer 7

.It is found in the very early embryo
.They can differentiate into all cell types therefore are pluripotent
.This is because all the genes in embryonic stem cells can be switched on so these cells can differentiate into any type of cell

Question 8

What is a tissue stem cell?

Answer 8

.They are found in the brain, skin, testicles, bone marrow, breast, intestines, muscles, & surface of the eye (cornea)
.They are involved in growth, repair and renewal of the cells that are found in a particular tissue
.They can differentiate into all of the types of cell found in a particular tissue type, therefore it is multipotent
.For example, blood stem cells located in bone marrow can give rise to red blood cells, platelets, phagocytes and lymphocytes

Question 9

What is a therapeutic use of stem cells?

Answer 9

.They are involved in the repair of damaged or diseased organs or tissues
.Such as corneal repair, and the regeneration of damaged skin/ Skin grafts
. Stem cells play a major role in the treatment of extensive burns and large ulcers through providing sufficient numbers of epidermal and epithelial cell lines that can be used in replacing damaged tissues

Question 10

What is a research use of stem cells?

Answer 10

.They are used as model cells to study how diseases develop or for drug testing
.It provides information on how cell processes such as cell growth, differentiation and gene regulation work
.Stem cells from embryos can self-renew in a lab under the right conditions, these would include suitable growth media and growth factors

Question 11

What are the ethical debates against embryonic stem cells?

Answer 11

.It involves the destruction of embryos
.A fertilised egg is a human being with a soul
.Their use is strictly regulated by the law

Question 12

How is a tumour formed?

Answer 12

. It is a mass of abnormal cells which are produced from cancer cells dividing excessively
. They divide excessively because they do not respond to regulatory signals

Question 13

How is a secondary tumour formed?

Answer 13

. Cells within the tumour may fail to attach to each other, and as a consequence can spread through the body to other tissues and organs where they form secondary tumours

Question 14

What is metastasis?

Answer 14

. It is the spread of cancer from its primary site throughout the body to other places where they form secondary tumours

Question 15

What are the stages of the formation of primary cancerous tumours and secondary cancerous tumours?

Answer 15

.Cancer cells divide excessively because they do not respond to regulatory signals
.This excessive cell division results in the production of a mass of abnormal cells, called a tumour
.Cells within the tumour may fail to attach to each other so can spread throughout the body to other tissues and organs
.The cancer spreads from its primary site to other places in the body where they form secondary tumours, which is also known as metastasis