Gene Expression

Question 1

Totipotent stem cells

Answer 1

Are able to produce any type of body cell

Only live for a very limited time during embryonic development in mammals where they only transfer part of their dna

Question 2

Pluripotent stem cell

Answer 2

Totipotent cells develop into pluripotent cells in embryos
Pluripotent cells are able to divide in unlimited numbers and produce any type of cell that makes up the body
They are used to treat human disorders

Question 3

Multipotent stem cells

Answer 3

Found in mature mammals and can divide into a limited number of cell types

Question 4

Unipotent stem cells

Answer 4

Found in Mature mammals

Can divide into a new cell but can only produce one type

Question 5

Main sources of stem cells

Answer 5

Adult stem cells, embryonic stem cells and induced pluripotent stem cells

Question 6

Benefits of using stem cells

Answer 6

To reduce preventable deaths e.g can grow organs to reduce the wait time for transplants
Treat conditions that decrease the quality of life e.g can be used to replace the damaged spinal cord in paralysis

Question 7

Induced Pluripotent stem cells

Answer 7

Can avoid the ethical issues of extracting pluripotent cells
They are produced from an adult somatic cell which are specialised
Somatic cells are converted to IPS cells by activating genes using protein transcription factors which makes somatic cells unspecialised
They can be made from the patients own body cells which reduces the chance of rejection

Question 8

Bone marrow transplant

Answer 8

Use multipotent stem cells

Question 9

Function of transcription factors

Answer 9

Proteins that enter the nucleus from the cytoplasm through nuclear pores

Question 10

Activators

Answer 10

They promote gene transcription by interacting with RNA polymerase and allowing it to bind to DNA

Question 11

Repressors

Answer 11

Stop RNA polymerase from binding to dna

Question 12

Peptide hormones

Answer 12

Bind to the cell membrane and trigger a secondary messenger response which leads to the activation or inhibition of transcription of some genes

Question 13

Lipid soluble steroid hormones

Answer 13

Can pass through the phospholipid bilayer and interact directly with dna

Question 14

Oestrogen

Answer 14

Lipid soluble steroid hormone

Question 15

How does oestrogen reach the nucleus

Answer 15

Diffuses through the cell surface membrane and through the nuclear pore in to the nucleus

Question 16

Epigenetic regulation

Answer 16

Interacts with dna to control the access of dna so dna alters gene expression without actually changing the genetic code

Question 17

Chromatin

Answer 17

The combination of dna and histones

Question 18

Epigenome

Answer 18

Chemical layer surrounding chromatic and interacts with it to change its structure
It can cause chromatin to become:
More condensed= prevents transcription factors from binding to dna
Or less condensed= allows easier access to transcription factors

Question 19

Epigenetic markers

Answer 19

Groups that do not alter the base sequence

Chromatin becomes more or less condensed when epigenetic markers are attached or removed from dna or histone proteins

Question 20

Increased methylation

Answer 20

Methyl groups bind to CpG sites on dna and cause chromatin to be more condensed so transcription factors can’t reach dna

Question 21

Acetylation of histones

Answer 21

Acetyl grpups are added to lysine amino acids on histone proteins which removes a bond between the histone and protein and the dna which causes it to be less tightly wrapped so RNA polymerase and transcription factors can more easily bind and therefore gene expression is stimulated

Question 22

Inheritance of epigenetic markers

Answer 22

Environmental factors such as methylation can influence the gene expression of their offspring

Question 23

Abnormal methylation

Answer 23

If methylation is not regulated properly this can affect the regulation of important processes
If increased too much it can decrease the gene expression of tumour suppressor genes so the cells divide uncontrollably
If decreases too much it can increase the expression of proto oncogenes too much

Question 24

Epigenetic change and treating disease

Answer 24

Epigenetic changes can be reversed
E.g the action of methyl transferase enzyme can be inhibited
Usually adds methyl groups to do dna which can cause disease

Question 25

RNA interference

Answer 25

Small molecule of double stranded RNA

Binds to the mRNA molecule and breaks it down which prevents it from being translated into a protein

Question 26

siRNA

Answer 26

Complimentary to the MRNA sequence it inhibits so it targets a specific sequence and breaks it down into smaller fragments

Question 27

Mirna

Answer 27

Not fully complimentary to the mRNA sequence so it can target multiple sequences

Question 28

Benign tumours

Answer 28

Not cancerous and don’t spread to invade other tissues

Question 29

Malignant tumours

Answer 29

Cancerous and spread into other tissues and around the body

Question 30

Tumour suppressor genes

Answer 30

Inhibit cell division to regulate the rate at which cells divide
Increased methylation of a tumour suppressor gene inihibts this gene

Question 31

Oncogenes

Answer 31

Capable of transforming a cell into a cancerous cell cause they cause excessive cell division
Mutations of a proto oncogene
Decreased methylation of a proto oncogene causes cell division

Question 32

Environmental factors that affect cancer

Answer 32

Exposure to radiation
Smoking
Alcohol consumption
Eating a diet high in fat

Question 33

Genetic factors that affect cancer

Answer 33

Having certain alleles such as the BRCA1 allele can increase the chance of developing breast cancer

Question 34

Prevention of cancer

Answer 34

Develop more sensitive tests to detect earlier on

Question 35

Treatment

Answer 35

If we know what gene mutations cause cancer, drugs can be developed to target these specific gene mutations and intensify the treatment

Question 36

How do transcription factors work

Answer 36

They are activated through a signalling pathway and bind to the promoter region of a gene which can either allow or prevent the transcription of the gene from taking place

Question 37

What do transcription factors interact with

Answer 37

RNA polymerase either by assisting RNA polymerase binding to the gene or by preventing it from binding

Question 38

Effect of transcription factors

Answer 38

Either increase or decrease the rate of transcription of a gene

Question 39

What does oestrogen do when in the nucleus

Answer 39

Attaches to an ERa oestrogen receptor that is held within a protein complex, this causes the ERa oestrogen receptor to under a conformational change

Question 40

What effect does the new shape of the ERaoestrogen receptor have

Answer 40

Allows it to detach from the protein complex and diffuse towards the gene to be expressed

Question 41

What does the ERa oestrogen receptor bind to

Answer 41

A cofactor which enables it to bind to the promoter region of the gene, this stimulates RNA polymerase binding and gene transcription

Question 42

Example of epigenetic links condition

Answer 42

Prader-Willi syndrome is caused by the silencing of an allele on chromosome 15
The severity of the syndrome depends on whether an individual receives the affected dna from their mother - carrier for the defective chromosome so won’t develop the syndrome but in the father they will

Question 43

SiRNA in the cytoplasm

Answer 43

In the cytoplasm siRNA’s bind to protein complexes which use energy from ATP to seperate the two strands of the siRNA which exposes the nucleotide babes so they are able to pair with bases from an mRNA molecule

Question 44

RNA interference : mRNA leaves the nucleus

Answer 44

In the cytoplasm single stranded siRNA binds to the target mRNA through complementary base pairing
The mRNA is cut into fragments by the enzyme/protein complex associated with siRNA - cannot be translated and therefore will not produce proteins