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