Controlling Gene Expression Flashcards
What is transcription factor
Protein that binds to the DNA in the nucleus and affect the process of transcribing DNA into RNA
Process of transcription factor
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.
What is the process of RNA splicing
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
Define epigenetics
Genetic control by factors other than the DNA sequence
Define DNA methylation
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
Define Demethylation
Removal of the methyl group from methylated DNA enabling genes to become active so they can be transcribed
Histone modification
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
Histone acetylation
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
Histone methylation
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
Define Cell differentiation
Occurs when unspecialised cells switch different genes on and off as needed to become specialised cells.
Cell differentiation process
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
Gene expression
If a gene is expressed it means it is transcribed from DNA to mRNA and translated from mRNA to produce a polypeptide chain
Transcription factors and promotor sequence process
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
What are histones
Histones are postively charged proteins. DNA helices coils around the histones to form chromatin - making chromosome
What are heterochromatin and properties
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
What are euchromatin propterties
Less condesned
Gene expressing
Gene rich (higher GC content)
Stains lighter
Histone acetylation what happen when removal of qcetyl group
—> removing an acetyl group produces heterochromatin again
Which then makes the chromatin comoact and inactivates genes
Define histones acetylation
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
Define histone methylation
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
Define induced pluripotent stem cells (iPS cell)
Adult cells that have been reprogrammed by the introduction of new genes to become pluripotent again
Properties of induced pluripotent stem cells
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
DNA methylation group and effect
Methyl
Silenced (switched off) as the DNA is tightly coiled around the histones (notranscription factors or RNA polymerase can bind to the promotor)
DNA demethylation group and acetyl
Switched on (expressed) - DNA is less tightly coiled so trasciption factors & RNA polyermase can bind to the promote to start transciption
Histones acetylation group and effect
Switched on (expressed) - DNA is less tightly coiled so trasciption factors & RNA polyermase can bind to the promote to start transciption
Histones methylation group and effect
Can result in genes being switched in or off
Histones demethylation group and effect
Acetyl and can result in genes being switched in or off
RNA splicing processes
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
Parkinsons disease
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
Type 1 diabetes
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
Damaged nerves
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
Organ for transplant
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
Ethical issues of stem cells
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
Benefits of stem cells
They could save many lives
They could have improve the quality and excellence of life for many people
Regulary authorities points
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
Process of RNA splicing
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)
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
RNA splicing
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
