OECG

🦚 OECG Created Tags Upstream region Consists of promoter/enhancer/silencer Describe the effects of methylation Methylation of residues at CPG Islands, particularly within transcription factor binding sites can physically hinder binding of transcription factors to DNA, blocking activators from accessing the promoter, preventing initiation of transcription and hence prevent gene from being expressed Recruit DNA binding proteins which in turn recruit other proteins such as histone deacetylase to the area, causing the chromatin to be compact further, preventing transcription Why is changes in CpG islands not regarded as mutational changes? Do not alter DNA sequence Outline the roles of non-coding DNA Non-coding DNA it codes for non-functional proteins Telomeres: They are non-coding tandem repeat sequences found at both ends of linear chromosomes Jul y 14 , 2025 1128 AM OECG 1

Telomeres determine the senescence( Aging) of cell as DNA polymerase unable to replace the RNA primer sequence at the ends of chromosomes due to absence of free 3OH group, causing the ends of chromosomes to shorten after each round of replication Since telomeres are non-coding, this ensures vital genetic information are not lost in each round Cells reaching critically short telomere length in one or more if its chromosomes will trigger a stop to its cell proliferation followed by apoptosis, preventing unlimited proliferation of cells Telomeres consists of non-coding DNA which protect important genes near the ends of linear chromosomes by providing a disposable buffer for the shortening of DNA after each round of replication due to the end replication problem before it starts losing genetic information The t-loop structure protects and stabilises the ends of chromosome, preventing the 3ʼ overhang from fusing with the ends of other chromosomes and also prevents the ends of chromosomes from being degraded by exonucleases The 3ʼ overhang of telomeres allows their own extension by providing an attachment point for correct positioning of enzyme telomerase Centromeres: Non-coding DNA consisting of tandem repeat sequences found at one location anywhere along the length of chromosome Allow sister chromatids to adhere to each other They allow kinectochore to attach where microtubules can then attach to kinectochore so that sister chromatid and homologous chromosomes can be separated to opposite poles Promoter: serves as a recognition site Which initiates a series of binding of multiple general transcription factors at the promoter which aid the RNA polymerase to bind to the promoter in the correct orientation, forming the transcription initiation complex to initiate transcription OECG 2

It also has critical elements such as TATA box that determines the precise location of transcription start site and CAAT and GC boxes to improve efficiency of promoter by recruiting general transcription factors and RNA polymerase to promoter Enhancer : is a r