Controlling Gene Expression

Question 1

What is transcription factor

Answer 1

Protein that binds to the DNA in the nucleus and affect the process of transcribing DNA into RNA

Question 2

Process of transcription factor

Answer 2

1) Transcription factors bind to the promotor region of the DNA which is found just upstream of the gene, this stimulate the start of transcription of the area of the DNA

2) Enhancer sequence
- when the transcription factor bind here, they change the structure of chromatin (wound-up DNA) making it more or less avaliable to RNA polymerase therefore controlling gene expression

Different transcription factors can switch on or switch off one gene, and so, this leads to great amounts of control, where if one transcription factor doesnt do the job, the other will.

Question 3

What is the process of RNA splicing

Answer 3

1) the mRNA produced in the nucleus result from the transcription of all DNA making up a gene
—> Exon (coding DNA)
—> Introns (non-coding DNA)
- pre-mRNA

• modification to the pre-mRNA always involve the removal of the intron and some cases exon are removed as well.
  2) “splicesome” enzyme join together, the exons that are transcribe and produced the mature functional mRNA
  3) splicesosome produce the final mature mRNA

4)Splicesosome join the same exons in variety of ways - RNA splicing
—> a single gene may produce several version of functional mRNA which is transcribed from the same section of DNA

5) These different version of mRNA code for different arrangement of amino acid, which in turn produce different polypeptide chains and therefore different proteins
—> result ina single gene producing several different phenotype
-> these post-transcriptional changes to mRNA lead to more variety in the phenotype

Question 4

Define epigenetics

Answer 4

Genetic control by factors other than the DNA sequence

Question 5

Define DNA methylation

Answer 5

Methylation of DNA (addition of a methy -CH3 group) to a cytosine in the DNA molecule next to a guanine in the DNA chain and prevents the transcription of a gene

Question 6

Define Demethylation

Answer 6

Removal of the methyl group from methylated DNA enabling genes to become active so they can be transcribed

Question 7

Histone modification

Answer 7

Histones are positivelt charged proteins, RNA helices wind around the hostones to form chromatin

• tightly packed chromatin (heterochromatin) means less genes are avaliable to transcibe
• active chromatin loosely held eith uncoiled regions of DNA making more genes avaliable for transcription so the new protein can be made

Question 8

Histone acetylation

Answer 8

An acetyl group (-COCH3) is added to one of the lysine in the histone structure. A

—> adding an acetyl group usually opens up the strcuture and activates the chromatin, allowing genes in that area to be transcribed

Question 9

Histone methylation

Answer 9

A methyl group (-CH3) is added to a lysine in the histones. Depending on the position of the lysine , methylation may cause inactivation of the DNA or activation of a region

• this causes inactivation og the DNA and is linked to silencing
• Methylation is often linked to the silencing of a gene and even whole chromosome

Question 10

Define Cell differentiation

Answer 10

Occurs when unspecialised cells switch different genes on and off as needed to become specialised cells.

Question 11

Cell differentiation process

Answer 11

1) chemical stimulus (eg methylation/transcription factor)
2) certain genes activated/switched
3) mRNA produced from these genes
4) RNA splicing
5) translation of mRNA to form polypeptide /protein
6) permanent modification of the cell
2) some genes switched on, other switch off
3) pre-mRNA produced from these gene
4) mRNA splicing occurs to modify the mRNA even more, producing the post or final mRNA
5) translation of mRNA produces a protein
6) the cell is permanently modified and its function is determined

Question 12

Gene expression

Answer 12

If a gene is expressed it means it is transcribed from DNA to mRNA and translated from mRNA to produce a polypeptide chain

Question 13

Transcription factors and promotor sequence process

Answer 13

Transcription factors bond to specific regions on the DNA called promotor sequences

Promotor sequence are found just above the starting point for transcription

The enzyme RNA polymerase, which makes a new RNA molecule from a DNA template, must bind to the DNA of the gene. It attaches at the promotor sequence

RNA polymerase can attach to the promotor only with the help of transcription factors. They are needed for the transcription of any gene

Question 14

What are histones

Answer 14

Histones are postively charged proteins. DNA helices coils around the histones to form chromatin - making chromosome

Question 15

What are heterochromatin and properties

Answer 15

When chromatin is super coiled and condensed, the genes arent not available to be copied and therefore cannot make proteins

• more condensed
• silenced genes
• gene poor (high AT content)
• stains darker

Question 16

What are euchromatin propterties

Answer 16

Less condesned

Gene expressing

Gene rich (higher GC content)

Stains lighter

Question 17

Histone acetylation what happen when removal of qcetyl group

Answer 17

—> removing an acetyl group produces heterochromatin again

Which then makes the chromatin comoact and inactivates genes

Question 18

Define histones acetylation

Answer 18

Addition of an acetyl group (-COCH3) to one of the lysines in the histone structure, which opens up the structure and activates the chromatin, allowing genes in that area to be transcribed

Question 19

Define histone methylation

Answer 19

Addition of a methy group (-CH3) to a lysine in the histone; methylation may cause inactivation or activation of the region of DNA, depending on the position of the lysine

Question 20

Define induced pluripotent stem cells (iPS cell)

Answer 20

Adult cells that have been reprogrammed by the introduction of new genes to become pluripotent again

Question 21

Properties of induced pluripotent stem cells

Answer 21

Induced pluripotent stem cells (iPS cells) can be produced from adult somatic cells using appropriate protein transcription factors to overcome some of the ethical issues with using embryonic stem cells

To do this, the genes that were switched off to make the cell specialised must be switched back on. This is done using transcriptional factor

Question 22

DNA methylation group and effect

Answer 22

Methyl

Silenced (switched off) as the DNA is tightly coiled around the histones (notranscription factors or RNA polymerase can bind to the promotor)

Question 23

DNA demethylation group and acetyl

Answer 23

Switched on (expressed) - DNA is less tightly coiled so trasciption factors & RNA polyermase can bind to the promote to start transciption

Question 24

Histones acetylation group and effect

Answer 24

Switched on (expressed) - DNA is less tightly coiled so trasciption factors & RNA polyermase can bind to the promote to start transciption

Question 25

Histones methylation group and effect

Answer 25

Can result in genes being switched in or off

Question 26

Histones demethylation group and effect

Answer 26

Acetyl and can result in genes being switched in or off

Question 27

RNA splicing processes

Answer 27

mRNA results from the transcription of all the DNA in a gene, including introns and exons

This mRNA is not finished immediately after transcription. There are several processes that occur to modify before it reachs the ribosome. This is refered to as pre-mRNA

Modification to the pre-mRNA always involve the removal of introns and sometimes exons as well

Enzyme complexes called spliceosome join togther the exons that are to be translated to produce the functional mRNA

The spliceosome may join the same exons in a variety of ways process known as RNA splicing

RNA splicing can result in a single gene producing different polypeptide chains and therefore different proteins

A single gene can therefore produce several different phenotype

Question 28

Parkinsons disease

Answer 28

Parkinson disease happens when the neurons that is responsible for producing dopamine in teh body stop working, and this causes the hands to statt shaking uncontrollably and eventually causes the whole body to stop moving . Scientists are hopeful that stem cells could replace these missing neurons and enavle the body to produce dopamine

Question 29

Type 1 diabetes

Answer 29

Type 1 diabetes develops when the islets of langerhans are lost or stop producing insulin, leading to uncontrollable glucose concentration which could be fatal. Even though insulin shots do exist, they are only temporary solution for a huge problem.

Scientist are tryinf ti get stem cells to form islet of langerhans ans then they would want to inject them into a type 1 diabetes patient, so that insulin can be produced once more, however currently not possible

Question 30

Damaged nerves

Answer 30

When this happens a part of the nerve may be cut off or stops working causing the body to experience permanent partial or full paralysis. Scientist are trying to see if stem cells can help regrow these damaged nerves so that people with this type of disability are able to gain some form of control again

Question 31

Organ for transplant

Answer 31

Many people die due to missing organs or malfunctoning ones and currently scientist are tyring to use stem cells in order to produce orgrans by manipulating pluripotency or their multipotency in specialization to produce these organs

Question 32

Ethical issues of stem cells

Answer 32

Embryo have the right to life, as they are genetically unique individuals

If adult stem cell are extracted, the process could bring a lot of discomfort to the individuals

Using embryonic stem cells by IVF the raise issue because once you extracted the stemcells the embryo is destroyed and the same embryo couldve develoepd into a fetus and eventually a human being

Question 33

Benefits of stem cells

Answer 33

They could save many lives

They could have improve the quality and excellence of life for many people

Question 34

Regulary authorities points

Answer 34

1) looking at research proposal to decide if they are allowed
2) licensing and monitoring centers - make sure that only trained staff are able to perform researched related to stem cells
3) producing guidelines and coe of practice - to make sure all scientist are following the same procedure during these research
4) monitoring development in scientific research - so that guidelines can be updated and any advancements made are benefited from
5) providing information to governments and professionals, this allows the society to understand why studying embryos is important and why they are involved

Question 35

Process of RNA splicing

Answer 35

1) when a RNA from the DNA of a gene in the nucleus both the introns and the Exons are transcribed
2) the introns and sometimes some of the exons must be removed from the pre-mRNA before it can be translated at the ribosome
3) this cutting and pasting of the pe-mRNA a is carried out by enzyme called splice so some
4) once the introns have been removed the splice so some joins up the exons in a variety of ways to produce different strands of mRNA for translation

5)

Answer 36

The splicesosome may join the same exons in a variety of ways in a process known as RNA splicing

—> as a result a single gene may produce several versions of functional mRNA which is transcribed from the same section of DNA . These different version of the mRNA code for different arrangements of amino acids, which in turn produce different polypeptide chains and therefore , different phenotype.

These post-transcription changes to mRNA leads to more variety in the phenotype than is coded for directly in the genotype

Question 37

RNA splicing

Answer 37

The DNA a is transcribed into mRNA by RNA polymerase from 5’ to 3’ direction

This transcription process produced premature mRNA which has the exons and introns on the mRNA . Premature mRNA is spliced to remove the intron (by protein snRNP) out

And joined together by splicesosome enzyme

The mature mRNA produced with