Stem Cells And Gene Expression

Question 1

Explain what is meant by the term totipotent and pluripotent.

Answer 1

Totipotent cells can differentiate into any type of human cell whereas pluripotent cells can only differentiate into certain cells

Question 2

Explain how cells produced from stem cell can have the same gene yet be of different types. 3points

Answer 2

Some genes are inactive
They are not transcribed because their transcription factor does not bind to promoter region on that dna

Question 3

Describe the mechanism by which a signal protein causes the synthesis of mRNA. 6points

Answer 3

Signal protein binds
to receptor on surface membrane
Messenger molecule moves from cytoplasm and enters nucleus
Releasing transcription factor
Binds to promotor region on DNA
Activates RNA polymerase to begin transcription of target gene

Question 4

Explain how oestrogen enables RNA polymerase to transcribe its target gene. 6 points

Answer 4

Oestrogen diffuses through cell membrane
Through the nuclear envelope
Binds to oestrogen receptor
Changes tertiary structure
Releasing transcription factor
Which binds to promotor region on DNA
stimulates RNA polymerase to transcribe target gene

Question 5

Explain how methylation of tumour suppressor gene can lead to cancer. 3points

Answer 5

Increased methylation causes less transcription of tumour suppressor gene
Protein not produced that controls cell division
so uncontrolled cell division (mitosis)occurs forming malignant tumours

Question 6

Describe how alterations to tumour suppressor gene can lead to the development of tumours

Answer 6

Increased methylation or mutation
Causes less transcription of tumour suppressor gene
So less production of protein which inhibits cells division(mitosis)
So uncontrolled cell division occurs

Question 7

Describe what is meant malignant tumour. 5point

Answer 7

Mass of unspecialised cells
Caused by uncontrolled cell division (mitosis)
Due to increased methylation or mutation within tumour suppressor gene
These cells can die and break off causing dna to travel through the blood
To different part of the body
Can grow forming new tumours

Question 8

Describe how altered dna may lead to cancer

Answer 8

mutation
Causes change in base sequence of tumour suppressor gene which inhibits cell division
protein not formed
Uncontrolled cell division occurs(mitosis)
Malignant tumour forms

Question 9

Define epigenetics

Answer 9

Change in hereditary phenotype unrelated to change in in DNA sequence