Division and Differentiation in Human Cells

Question 1

What is a somatic cell?

Answer 1

Any cell which is not involved in reproduction.
Somatic cells are diploid (23 pairs of homologous chromosomes)
They divide by mitosis to produce more diploid somatic cells.

Question 2

What are germline cells?

Answer 2

Gametes (sperm and ova) and the stem cells that divide to form gametes.
Germline stem cells are diploid and contain 23 pairs of homologous chromosomes.

Question 3

What are homologous chromosomes?

Answer 3

These are chromosomes which have:
Tha same size
Same centromere position
Carrying the same genes at the same loci (location on chromosome)

Question 4

How do germline cells divide?

Answer 4

Germline cells can divide by mitosis, to produce new diploid germline cells, but also by meiosis, to produce new haploid gametes.

Question 5

What is the chromosome compliment of gametes?

Answer 5

Haploid - 23 single chromosomes.

Question 6

Why do germline cells divide by mitosis?

Answer 6

Germline cells divide by mitosis to produce more germline cells.
The nucleus of the germline cells can divide by mitosis to maintain the diploid number of chromosomes.

Question 7

Why do germline cells divide by meiosis?

Answer 7

Germline cells divide by meiosis to produce haploid gametes (sperm and ova)

Question 8

The nuclues of Germline cells can divide by meisosi, it under goes two divisions. What happends during these divisons ?

Answer 8

Divison 1 - Seperation of homologous chromosomes.
Divison 2 - Seperation of chromatids.

Question 9

When do specialised cells arise ?

Answer 9

Specialised cells arise from the differentiation of unspecialised cells (stem cells) during embryological development.

Question 10

What are specialised cells?

Answer 10

Cells which have adapted to perform particular functions.

Question 11

What is cellular differentiation

Answer 11

Cellular differentiation is teh process by which a cell expresses certain genes to produce proteins characteristic for that cell type - this allows cells to carry out specialised functions.

Question 12

What genes are switched on all the time for all cell types (vital metabolities)

Answer 12

Genes which code for enzymes for aerobic respiration, proteins for cell organelles and proteins for cell membranes.

Question 13

What genes are switched on only in specific cells (specific metabolites)

Answer 13

Genes which code for antibodies, hormones, digestive enzymes and structural proteins

Question 14

What are stem cells?

Answer 14

Stem cells are unspecialise cells that have the ability to self renew (by mitosis) and/ or differentiate into a diverse range of specialised cells.

Question 15

What are the two types of stem cells?

Answer 15

Embryonic and tissue

Question 16

What are embryonic stem cells

Answer 16

Embryonic stem cells are derived from an embryo about 4-5 days old (blastocysts)
Stem cells in these very early embryo can differentiate into all of the cell types that make up the individual.
They are said to be pluripotent.
All genes in an embryoniuc stem cells can be switches on so these cells can differnetiate into any cell type.

Question 17

What are tissue stem cells?

Answer 17

Tissue stem cells are involved in growth, repair and renewval of the cells that are found in tissues.
Tissue stems cells are said to be multipotent - this means that they can differentiate into all of the cell types found in a particular tissue type.

Question 18

What parts of the body are tissue stem cells found in?

Answer 18

Brain, Heart, Bone Marrow ect

Question 19

What are blood stem cells?

Answer 19

A type of tissue stem cell.
Located in bone marrow
Give rise to WBCs (phago and lymphocytes), RBCs and platelets.

Question 20

What are the two main uses of stem cells.

Answer 20

Therapeutic and Research uses

Question 21

What are theraputic uses of stem cells

Answer 21

Therapeutic uses of stem cells involve the repair of damaged or diseased organs or tissues.
They can be used in corneal repair and the regeneration of damaged skin.
(This is made possible since stem cells taken from an embryo can self renew, under the right conditions in the lab- they are cultured in vitro and transplanted into the damaged area)

Question 22

What are research uses of stem cells.

Answer 22

1) Study how diseases develop.
2) Drug Testing (stem cells act as model cells)
3) Provide information about cell processes such as growth, differentiation and gene regulation work

Question 23

Why is the use of embryonic stem cells controversial?

Answer 23

Uses of emryonic stem cells can offer treatments for diseases and injury; however, it invloves destruction of embryos.

Question 24

What is cancer?

Answer 24

The excessive and uncontrolled divison of abnormal cells.

Question 25

What are the stages of cancer developing ?

Answer 25

1) Most cancers originate from a cells undergoing successive mutations to the genes involved in cell division.
2) Cancer cells divide excessively and uncontrollably, because they do not respond to regulatory signals.
3) This results in a mass of abnormal cells called a tumour.
4) If cancer cells within the tumour fail o attach to each other, they spread through the body where they form secondary tumours.

Question 26

Explain genetic mutations and cancer

Answer 26

Most cancers originate from a cell undergoing successive mutations to the genes involved in cell divisions.
If cell division is not regulated, the cell can divide excessively and uncontrollably.
It takes a long time for successive mutations to occur which is why the risk of developing cancer increases with age.

Question 27

What are carcinogenic agents ?

Answer 27

Exposure to carcinogenic agents (cancer causing) can increse the risk of developing cancer. These include things such as;
-smoking
-pollution
- over exposure of skin to ultraviolet radiation
Carcinogenic Agents increase the rate of mutations occuring

Question 28

What places is cancer more common and why?

Answer 28

Cancer is more common in skin, lung and bowel tissue as the mutation rate is greater there than in other cells, due to more exposure to carcinogens.

Question 29

Why does the risk for getting cancer increase with age?

Answer 29

It takes a long time for the successive mutations to occur