CONTOL OF GENE EXPRESSION

change in base sequence of DNA occurs during DNA replication

chemical or radiation that increases mutation rate .Base analogs: can substitute for base eg. 5-bromouracil can substitute for Thymine, but pairs w/Guanine instead of Alanine .Altering bases: eg. alkylating agents add an alkyl to Guanine so changing its structure so that it pairs w/Thymine instead of Cytosine .Altering DNA structure: eg. Ultra Violet radiation can cause adjacent Thymines to pair

One extra base is added to the DNA sequence causes all subsequent codons to be altered-frameshift

One base is deleted in the DNA sequence causes all subsequent codons to be altered-frameshift

One base in DNA sequence is changed no frameshift only one codon changes may have no impact due to degenerate genetic code

section of bases detach from DNA sequence and re-join inverted results in different amino acids being coded for in this region

One base is duplicated at least once in sequence causes frameshift to right

section of bases on one chromosome detaches and attaches to different chromosome

change in all the codons after point of mutation each base shifts left or right one position

• DNA base sequence • mRNA codons • amino acid sequence • ionic/H/disulphide bonds • tertiary structure

Some mutations, such as substitutions, change only one triplet code in DNA-degenerate nature of genetic code this means that sequence of amino acids will not change

.May affect location of ionic/hydrogen/disulphide bond between R groups .Change tertiary structure of protein .May create nonfunctional protein

Protein w/different primary and tertiary structure- shape is changed it cannot carry out its function + prevent enzyme-substrate complexes from forming

undifferentiated cells that can continually divide and become specialised

divide and produce any type of body cell .Only present for limited time in first few divisions of mammalian embryo .During development not all stem cell genes are expressed, so some are not transcribed or translated to proteins .genes that are expressed lead to synthesis of proteins that determine cell structure and function-cell is now specialised and this is irreversible

Embryonic stem cells that can divide in unlimited numbers and develop to most of body’s cell types can be used to treat human disorders, as they can differentiate to any body cell- get from 4-5 day old embryos that are spare from being used in IVF In vitro fertilisation treatment and rest of embryo is destroyed leads to ethical concerns regarding their use in research and treatment

Adult cells that can develop into limited number of cell types have an operation to obtain bone marrow cells from donor that can develop to red blood cells or white blood cells Can be used to replace variety of different cell types but it is limited-Requires donation of stem cells from genetically compatible donor – reduces chance of rejection, but rejection is still possible Reliance on donors is an issue due to lack of suitable donors Has less ethical issues as donors are usually consenting adults

Can only differentiate to one type of cell E.g. Cardiomyocytes are highly specialised heart muscle cells- are very specialised, they cannot regenerate by mitosis themselves- formed from one type of unipotent stem cell that divides and differentiates to cardiomyocyte

.Take somatic adult specialised cells, and infect them w/modified virus w/genes coding for transcription factors so that cells become pluripotent .Transcription factors attach to promoter region of DNA and stimulate RNA polymerase to stimulate transcription .cells divide and differentiate to desired cells

cells modified come from patient themselves- reduces chance of rejection when new cells are transplanted back in

Benefits: All stem cell treatments in medicine provide long term treatment as they continuously divide Stem cells could be used to grow organs to save lives, or replace eye tissue Bone marrow stem cells are already being used to treat leukaemia and have been used to cure HIV Issues: Obtaining embryonic stem cells involves destruction of an embryo Better to use adult stem cells e.g. iPS which could possibly be made from patient’s own cells-cells continuously dividing increases risk of uncontrollable cell division and production of tumours nonfunctioning cells must be destroyed e.g. by chemotherapy treatment, before new functioning stem cells are injected – this can be painful and increase chance of infection

ability of gene to be transcribed to mRNA and translated to polypeptide

section of DNA before gene where RNA Polymerase binds

proteins which bind to promotor region on DNA they move from cytoplasm to nucleus and stimulate RNA polymerase to produce mRNA + Inhibit binding of RNA polymerase preventing production of mRNA