gene expression

mutations are changes in the sequence of nucleotides in DNA

the different types of mutations iclude: -insertions/deletion • duplication • inversion • translocation

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

this is when one or more bases are repeated and therefore produces a frameshift

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

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

these include alcohol, benzene and substances in asbestos and is tar in tobacco

alpha, beta and also UV and X rays

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

stem cells are undifferentiated cells which can keep dividing to give rise to other cell types

types of stem cells include: • pluripotent • totipotent cells • multipotent • unipotent

pluripotent cells are cells that are able to five ride to many tupes of specialised cells apart from embryonic cells

totipotent cells are cells that can five rise to all types of specialised cells including embryonic 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

these are cells that can only differentiate into one type of cell

pluripotent cells also have a number of different uses in repairing damaged tissue

pluripotent stem cells can also be created from unipotent stem cells and are therefore known as induced pluripotent stem cells (iPS)

oestrogen has the ability to alter transcription through altering molecules called transcription molecules

these are molecules that bind to a specific site on DNA to begin the process of 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

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

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

DNA methylation DNA acetylartion

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