Handout #8 ANSWERS

Handout #8 ANSWERS - Handout #8- ANSWERS Todays topics: o...

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Handout #8- ANSWERS Today’s topics: o Gene expression o Transcription o Translation Central Dogma of Molecular Biology: Transcription and Translation DNA → RNA → poly peptide/protein/enzyme Where do the processes of transcription and translation occur in prokaryotes and eukaryotes? Transcription- the template strand of DNA is copied into mRNA Translation- the mRNA template is used to make a polypeptide Transcription in Eukaryotes Where does transcription occur in eukaryotes? See Fig 15.6 (next page) Following transcription, the RNA is not ready for translation. This pre-mRNA undergoes changes before exported from the nucleus into the cytoplasm where ribosomes carry out translation Following transcription, pre-mRNA is modified… A 5’cap is added to the 5’ end of the mRNA soon after transcription begins At the 3’ end of the gene is a sequence called the polyadenylation signal; this sequence is cleaved from the mRNA and poly(A) polymerase adds a chain of adenines (50+) to the 3’ end; this is called the poly(A) tail The gene contains sequences called introns and exons; the introns are removed from the pre-mRNA molecule in a process called splicing, which leaves only the exons in the final mRNA molecule Why do genes contain introns and exons? mRNA splicing Small ribonucleoprotein particles – snRNPs, which consist of small nuclear RNA (snRNA) and proteins, form a complex called a spliceosome
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The spliceosome can remove specific introns from the mRNA without removing any of the exons Alternative splicing- exons can be joined in varying combinations, resulting in the formation of multiple proteins from a single gene o Related proteins can be made from a single gene o Example- alternative splicing of α-tropomyosin results in the formation of either smooth muscle or skeletal muscle
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Translation in Eurkaryotes Following pre-mRNA processing into mRNA, the mRNA travels into the nucleus where it is used a template for making a polypeptide.
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Handout #8 ANSWERS - Handout #8- ANSWERS Todays topics: o...

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