Gene expression

Question 1

What is a stem cell?

Answer 1

Undifferentiated/unspecialised cell

Question 2

Define the term totipotent

Answer 2

Stem cells can differentiate into any cell type

Question 3

Define the term pluripotent

Answer 3

Stem cells that can make all cell types except extra embryonic tissue

Question 4

Define the term multipotent

Answer 4

Stem cells that can only produce a certain cell

Question 5

How are IPS stem cells produced?

Answer 5

Turning adult cells into pluripotent cells using transcription factors

Question 6

What is the role of oestrogen in gene expression?

Answer 6

Oestrogen enters the cell and binds to transcription factor

Question 7

How are siRNA made?

Answer 7

A double stranded RNA molecules is cut into small sections, made single stranded and combined with RISC enzyme

Question 8

How do siRNA function?

Answer 8

Complementary to mRNA. They then cut up the molecule so translation cannot occur

Question 9

What is a transcription factor?

Answer 9

Controls the expression or transcription of genes

Question 10

What type of transcription factor prevents transcription?

Answer 10

Repressors

Question 11

What is a processing body?

Answer 11

Where an mRNA is degraded after being broken into fragments by associated proteins. miRNAs can be stored here to be transcribed at another time

Question 12

What is epigenetics?

Answer 12

Heritable changes in gene expression without changing the DNA sequence caused by the environment

Question 13

How does chromosomes being condensed affect gene expression?

Answer 13

Reduces transcription as transcription factors cannot reach the DNA and therefore the promoter

Question 14

How does loosening chromosomes affect gene expression?

Answer 14

Increases transcription as transcription factors can now bind to the promoter region of DNA

Question 15

What affect does increased DNA methylation have?

Answer 15

Deceases gene expression. Also, causes chromosome condensation

Question 16

What affect does decreases acetylation have?

Answer 16

Less acetyl groups mean increases positive charges on the histones so they are more attracted to the negative DNA resulting in increased condensing of DNA and reduced gene expression

Question 17

What is a mutation?

Answer 17

A change to the DNA Base sequence

Question 18

What is the difference between substitution and deletion mutations?

Answer 18

A substitution is the replacement of one base for another whereas a deletion involves the removal of a base, resulting in a frame shift

Question 19

Why is a deletion mutation more dangerous?

Answer 19

Causes a frame shift and causes all triplet codes after the mutation to change resulting in different amino acids and the protein not being produced.

Question 20

Why can some substitution mutations be silent?

Answer 20

The new triplet code codes for the same amino acid due to the genetic code being degenerate

Question 21

What is cancer?

Answer 21

Uncontrolled cell division

Question 22

What is the difference between a malign tumour and a benign tumour?

Answer 22

Malignant grow faster, can metastasize, have whole body effects and requires surgery

Question 23

What two genes control cell division?

Answer 23

Proto-oncogenes and tumour suppressor genes

Question 24

What affect do tumour suppresser genes have?

Answer 24

Inhibits cell division by producing a protein that inhibits it

Question 25

What affect do proto-oncogenes have?

Answer 25

Produce a protein/growth factor that stimulates cell divison

Question 26

How can a mutation to a proto-oncogene cause cancer?

Answer 26

A mutation can lead it to constantly be expressed and so constantly producing the growth factor that stimulates cell division

Question 27

How can a mutation to a tumour suppressor gene cause cancer?

Answer 27

Mutation leads to loss of protein that inhibits cell division resulting in uncontrolled cell division

Question 28

How could methylation cause cancer?

Answer 28

Increased methylation of tumour suppressor genes leading to inhibition of TSG leading to loss of protein that stops cell division.

Question 29

What is a frameshift?

Answer 29

A shift in the base triplets that follow on from the mutation

Question 30

What are the environmental risk factors for cancer?

Answer 30

• Increased alcohol consumption
• High fat diet
• Smoking
• Viruses
• Exposure to radiation
• Dangers in the workplace

Question 31

If a person has a mutated BRCA1 gene, what preventative measures can be carried out?

Answer 31

Mastectomy or increased screening for tumour formation

Question 32

What is a colonoscopy?

Answer 32

Inserting a camera into the colon. Can be used to screen for tumour formation

Question 33

How can gene therapy treat cancer?

Answer 33

A faulty allele can be replaced by a functioning allele and this will hopefully stop tumour growth

Question 34

What is a phenotype?

Answer 34

Characteristics a person expresses

Question 35

How can overeating be caused be genetic and environmental factors?

Answer 35

Environment- High food availability
Genetics- People having lower dopamine receptors

Question 36

What is a twin study?

Answer 36

Studying identical twins to determine whether something is due to environmental or genetic factors

Question 37

Why is a large sample size important?

Answer 37

More representative of the population

Question 38

Give an example of where a twin study has been used

Answer 38

Alzheimer’s disease. Found that sometimes both identical twins didn’t develop the disease so there must be some environmental factors