3C- Controlling Gene Expression

Specific region on the DNA to which transcription factors bind to stimulate transcription

specific region of DNA to which transcription factors bind and regulate the activity of the DNA by changing the structure of the chromatin= open\closed chromatin structure

active Gene expression

Gene inactivity

• protein that binds to the DNA in the nucleus and affects the process of transcribing DNA to RNA • allowing different genes to be expressed or repressed

• changes that affect gene expression • example: DNA methylation, histone modification • involved in differentiation

• gene switched off • methyl groups are placed on DNA by a DNA methyltransferase enzyme • they are added to base of cytosine or adenine • methyl group changes the arrangement of the DNA molecule and prevents transcription from taking place • modifies the structure of histones • always silences a gene or sequence of genes

• genes switched on • removal of methyl groups • allows genes to become active again so they can be transcribed

• genes are deactivated or activated in stem cells • because of DNA methylation/histone binding • therefore the same genes will be activated in the daughter cells

• positively charged proteins • DNA helices wind around the histones to form chromatin • the histones determine the structure of the chromatin

• when chromatin is densely coiled and condensed around histones and the genes are not available to be copied to make proteins

• acetyl group is added to lysine in histone • this opens up the structure and activates the chromatin • allows genes in that area to be transcribed • removing an acetyl group causes heterochromatin

• methyl group is added to lysine in histone • depending on position of lysine, methylation causes either inactivation or activation of DNA region • silences genes, such as one of the X chromosomes in every female

• transcribed but not used (does not code for proteins) • do not leave nucleus • bind to DNA, inactivates (hides) the DNA • affects transcription of DNA code • modifies chromatin structure or modifies the products of transcription • genes and whole chromosomes can be silenced by ncRNA • also responsible for deactivating one of the X chromosomes in females (in order to maintain the balance of gene products in males and females)

• Transcriptional Control - transcription factors (proteins bind to DNA sequences, enhancer, silencer - Epigenetics (DNA methylation, demethylation, histone modification - non-coding RNA • Post Transcriptional Control - RNA splicing (Intron/Exon) • Post Translational Control - proteins modified in Golgi

segments of a DNA or RNA molecule containing information which does not code for proteins or a peptide sequence

• parts of gene that code (expressed) segments of a DNA or RNA molecule containing information that codes for a protein or peptide sequence

• modifications of proteins after they have been synthesized - proteins modified in golgi

• there is a chemical stimulus which causes DNA methylation/gene expression change • genes are activated or deactivated • activated genes will produce mRNA • mRNA translated into protein • protein permanently modifies cell

• this modification to the pre-mRNA always involves the removal of the introns and some of the exons • enzyme complexes known as spliceosomes join togeter the exons that are to be transcribed and produce the mature, functional mRNA • the spliceosomes may join the same exons in a variety of ways

• a single gene may now produce several versions of functional mRNA which is transcribed from the same section of DNA • these different versions of mRNA code for different arrangements of amino acids, which produce different polypeptide chains, and therefore different proteins • ultimately this can result in a single gene producing several different phenotypes • this is one way that the genotype can produce more proteins than there are genes