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Lecture 4

Lecture 4 - Transcription and Translation.docx

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BIOL 1000
Michael Gadsden

Lecture 4 - 21/10/10 Test will be about 30 – 35 MULTIPLE CHOICE QUESTIONS  Look at WHOLE question, try and answer the question without reading the answers, look for correct answers 5 – 7 True or False Questions Life Cycle of an mRNA (Moodle Animation)  Nucleus is a double membrane (both phospholipid bilayers and are very similar) o Has large nuclear pores called “gates”  Chromatin o DNA + all the proteins that are attached to it o Heterochromatin is VERY TIGHTLY WOUND  Usually no transcription occurs at chromatin  This is because of the proteins that bind to hChromatin allow no space for certain proteins like RNA Polymerase o Euchromatin  Less tightly wound  Are areas of active gene expression  NB: Genes only make up < 10% of your DNA o A chromosome will be partly Euchromatin and some will be Heterochromatin  Some heterochromatin stays that way (is known as constitutive hChromatin)  At certain times, some heterochromatin can change to euchormatin and vice- versa  This is because sometimes we want genes to be turned on or off, thus they must be turned on or off for when they are specifically needed.  The breakage of ionic bonds is what expresses this is called remodelling o Chromatin is specific to eukaryotes because in bacteria, the genes are smaller and are always on  Promoter o The control region (DNA Sequence) where transcription factors (a type of protein) bind and initiate RNA synthesis because RNA polymerase will bind to the specific transcription factors (proteins) o In a sense, transcription factors control which genes are expressed o Cancer cells can change this in order to bind to the cancer creating genes, the transcription is altered o PO 4auses changes!  5` methyl Guanine cap (added post transcriptional) (see sheet for drawing)  Introns (eukaryotes only) are removed by spliceosomes  Non-coding section of DNA within a gene  See sheet  3` Poly-Adenine tail (post-transcription) o Very long and they are degraded initially before the mRNA o Occurs in the nucleus  The proteins on the mRNA go back into the nucleus (directionality)  Initiation factors – proteins that bind mRNA to initiate translation o Any problems with these small steps can cause immense trauma on the body  eIF – eukaryote Initiation Factor  Small ringed RNA structure is tRNA attached to Methianine  RIBOSOMES o 40S – small eukaryotic ribosome subunit o 60S – large subunit o 80S – Full unit  The first signal to put an amino acid is “5` AUG 3`”the start codon (codes for Methianine)  The final signal is something like “5` UAA 3`”  Poly A tail shortens during translation to a critical length  then the mRNA is degraded  mRNA ½ life (length of time for only ½ to be not damaged) is between 2 seconds to 2 hours (this depends on the genes of origin)  eIF helps RNA Polymerase find whe
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