gene expression Flashcards
what are mutations
mutations are changes in the sequence of nucleotides in DNA
what are the different types of mutations
the different types of mutations iclude:
-insertions/deletion
- duplication
- inversion
- translocation
what is insertation/ deletion
it is where one or more nucleotide pairs are inserted or deleted from the sequence
This type of mutation alters the sequence of nucleotide after the insertions/deletion point known as a frameshift
what is duplication
this is when one or more bases are repeated and therefore produces a frameshift
what is translocation
This is when a sequence of bases is moved from one location in the genome to another
This could be movement within the same chromosome or movement to a different chromosome
what are the different causes of gene mutation
gene mutation can arise spontaneously during DNA replication, and can be caused by MUTAGENIC AGENTS that affect DNA, causes of gene mutations are:
- Chemical mutagens
- ionising radiation
- spontaneous errors
what are chemical mutagens
these include alcohol, benzene and substances in asbestos and is tar in tobacco
what is ionising radiation
alpha, beta and also UV and X rays
what effects do mutations have on the body
mutations can either have neutral effects where the mutation causes no change to the organism, e.g. in a case where the mutation occurs in a non-coding region of DNA or is a silent mutation
A mutation can also be neutral when a change in the tertiary structure of the protein has no effect on the organisms
sometimes, mutations can be beneficial
what are stem cells
stem cells are undifferentiated cells which can keep dividing to give rise to other cell types
what are the different types of stem cells
types of stem cells include:
- pluripotent
- totipotent cells
- multipotent
- unipotent
pluripotent cells
pluripotent cells are cells that are able to five ride to many tupes of specialised cells apart from embryonic cells
what are totipotent cells
totipotent cells are cells that can five rise to all types of specialised cells including embryonic cells
what are multipotent cells
they are cells that cen differentiate into other cell types but are more limited e.g. the cells in the bone marrow and umbilical cord
what are unipotent cells
these are cells that can only differentiate into one type of cell
what are the uses of pluripotent cells
pluripotent cells also have a number of different uses in repairing damaged tissue
how can pluripotent stem cells be created
pluripotent stem cells can also be created from unipotent stem cells and are therefore known as induced pluripotent stem cells (iPS)
what is the role of the hormone oestogen
oestrogen has the ability to alter transcription through altering molecules called transcription molecules
what are transcription molecules
these are molecules that bind to a specific site on DNA to begin the process of transcription
how does oestrogen control transcription
- the lipid soluble nature of oestrogen means that it can freely diffuse across the cell membrane where it binds to a receptor molecule on a transcription factor
- the binding alters the shape of the DNA binding site on the transcription factor and makes it able to bind to the DNA
- The transcription factor therefore enters the nucleus via the nuclear pore where it binds to DNA. This stimulates the transcription of the gene that makes up the DNA
what is small interfering RNA
Small interfering RNA (siRNA) also called silencing RNA is used for short term switching off of genes
The siRNA binds to a complementary sequence of mRNA.
As mRNA is usually single stranded and the cell there frore detets the double stranded form on mRNA and views it as abnormal
Therefore the mRNA is broken down by enzymes preventing translation
what are epigenetics
epigenetics involve heritable changes in gene function without changes to the bse sequence of DNA
It show that environmental factors can make changes to the function of genes which can be inherited
what are two examples of epigenetic changes
DNA methylation
DNA acetylartion
what is DNA methylation
it is the process by which methyl groups are added to DNAA
Methylation modifies the fuunction of DNA, typically acting to suppress gene transcription.
DNA methylation alters the expression of genes in cells as they divide and become specialised.
The change is permanent and prevents the cell from converting back into a stem cell or a different cell type
The methylation is through the addition of CH3 chemical group to cytosine bases, which both prevents binding of transcriptional factors to DNA and stimulated decreased acetylation of histones
what is DNA acetylationn
DNA acetylation also changes DNA structure.
Histones are positively charged proteins closely associated with DNA, which is negatively charged
Decreased acetylation of histones increases their positive change, so they bind DNA more tightly.
When this happens transcriptional factors can no longer access the DNA, so the gene is switched
how does cancer arise
it can arise as a result of muation
Uncontrolled cell division in cancer leads to the formation of a timour
There are two types of
what are the two types of tumours
benign
malignant
what are benign tumours
this means they do not tend to cause much harm about from mechanical damage caused by pressing against blood vessels or other cells
benign tumours grow slowly and do not spread
what are malign\ant tumours
malignant tumours grow rapidly and can spread to the neighbouring cells via METASTASIS (through the bloodstream or lymphatic system) this causes damage by disrupting the running of important processes
Malignant tumours are difficult to treat in comparison to benign
what plays a role in developing cancer
proto-oncogenes
oncogenes
tumour suppressor genes
abnormal methylation of tumour suppressor genes and oncogenes
increased oestrogen concentration
proto- oncogenes
These stimulates cells to divide by producing proteins that stimulate cell division allow the checkpoints of the cell cycle to be passed and can cause cancer if mutated
oncogenes
these are formed from mutated proto-oncogenes and result are permanently switched on resulting cell division that is uncontrolled. It does this by permanently activating a cell surface receptor or coding for a growth factor
tumour suppressor genes
They control cell divison, this causes the cell cycle to stop when damage is detected. They also play a role in the programming of apoptosis (cell death). When these are switched off the cell cycle becomes unregulated
abnormal methylation of tumour suppressor genes and oncogenes
increased methylation also called hyper-methylation plays an important role in controlling tumor suppressor genes and oncogenes. The hyper-methylation of a tumour suppressor gene called BRAC1
increased oestrogen concentration
this is linked to breast cancer development. These elevated levels are found in fatty tissues called adipose tissue in the breast of post menopausal women. Oestrogen binds to the transcription factor which activates the gene promoting cell division, leading to tumour formation
what are sequencing projects
sequencing projects have read the genome of a wide range of organisms, including humands the genome of simpler organisms allows the sequecnes of the proteins that derive dorm the genetic code of organisms to be determined
what has been the appliaation of sequecning genomes
this allows:
the idenfircation of potential antigens for usein vaccine production
why has the knowlege of the genome cannot be easily trasnlated for more complex organisms
the presence of non-coding DNA and of regulatory genes means that knowledge of the genome cannot be easily translated into the proteome
However, dude to selective gene expression not all of these proteins will be found in every cell in the body
what is the proteome
it is all the proteins that the genome can code for
why is gene sequencing importanst
it allows for genome wide comprarison between individuals and between species
Comparing genomes between species is significant as it allows evolutionary relationship between species to be determine and it is also is beneficial in medical research
it is also useful in the study of human disease
why is gene sequencing useful in medical research
comparing the genome of individuals enables differences to be identified which can then be used for development of personalised medicine tailored to a particular genome as well
what else has genome wide comparison made possible
it has allowed the sequencing of amino acids in polypeptides to be predicted and has allowed for the development of synthetic biology
what is the genome projects
The Human Genome Project is an international scientific project which has successfully
determined the sequence of bases of a human genome
what is the potential application of the genome wide project
screening for mutated sequences,
carriers
and pre-implantation screening as well as
screening for disorders such as Huntington’s disease before symtoms appear
what are the ethical issues regarding the human genome project
- people can become discriminated against due to their genetic disease
- the misuse and ownership of the genetic information
what is recombinant DNA technology
it involves the many ways in which we can manipulate DNA
