Normal Differentitation And Abnormal Division

Question 0

What do a group of cells with the same function form?

Answer 0

Tissue.

Question 1

What are specialised cells described as?

Answer 1

Differentiated.

Question 2

What does grouped tissue form?

Answer 2

Organs which combine the the functions of the tissue. The stomach has muscles to churn food.

Question 3

The growing points of plants have regions which are able perform cell division. What are these points called?

Answer 3

Meristems.

Question 4

What are meristems? In terms of ability to divide?

Answer 4

Totipotent and they can differentiate into any other type of cell.

Question 5

What cells do mammals have?

Answer 5

Adult stems which are regions of specialised cells which have differentiated and can only perform a restricted number of functions. Eg bone stem cells can only produce new bone cells.

Question 6

How do cells become differentiated?

Answer 6

A different combination of genes being expressed some genes are switched on and some off. This effect is permanent. This is why specialised cells cannot differentiate into others.

Question 7

What cells have the ability to produce any cell type?

Answer 7

Embryonic stem cells, this property is lost when organisms develop.

Question 8

What are the ethical concerns with using embryonic stem cells to replace damaged adult stem cells.

Answer 8

The process in which they are obtain usually from aborted foetuses. However we can now treat adult stem cells so that they behave more like embryonic stem cells.

Question 9

What controls gene expression in eukaryotic cells?

Answer 9

A variety of mechanisms; they may include changes to a histone protein of nucleosome or methylation of cytosine nucleotides.

Question 10

What controls gene expression in prokaryotic cells?

Answer 10

The lac operon.

Question 11

What does the regulator gene do?

Answer 11

Codes for a repressor molecule.

Question 12

What does the repressor molecule do?

Answer 12

Binds to the operator or the inducer.

Question 13

What does a structural gene do?

Answer 13

It make beta-galactosidase, an enzyme which breaks down lactase.

Question 14

What is the operator?

Answer 14

A length of DNA ‘upstream’ of the structural gene.

Question 15

What does the inducer molecule do?

Answer 15

In this case lactase binds to the repressor molecule.

Question 16

What does the system like when no lactase is present?

Answer 16

The regulator gene makes the repressor molecule. This attaches to the operator so the transcription enzyme cannot read the structural gene. No beta-galactosidase is made and the bacterium does not waste energy making an enzyme it does not need.

Question 17

How does the system work when lactose is present?

Answer 17

It acts as the inducer to cause the production of beta-galactosidase. The regulator still makes the repressor molecule but now the inducer attaches to it. This leaves the operator open so the transcription enzyme can read the structural gene, beta-galactosidase is produced and lactose can be broken down.

Question 18

What are proliferation genes?

Answer 18

Genes that code for proteins which promote cell division when an external cell is received. Eg when a wound needs to be repaired.

Question 19

What are proliferation genes also known as?

Answer 19

Proto-oncogenes because when they mutate they form form oncogenes which are found in many cancers. These mutations give proteins with abnormal cell division which stimulate excessive cell division and tumour formation even in the absence of any external signal. Because a mutation only has to happen in one gene of the pair, oncogenes can be thought of as dominant alleles.

Question 20

What are anti-proliferation gene?

Answer 20

Genes that codes from proteins which restrict cell division by operating at the cell cycle check points.

Question 21

What are anti-proliferation genes known as?

Answer 21

Tumour suppressor genes because they normally prevent excessive cell division. One functioning gene can still produce the protein inhibit the cell cycle, so both copies of the gene must mutate before the control of the cell cycle is lost and a tumour starts to form. For this reason, the cancer-causing mutations to anti-proliferation genes can be though of a recessive.