Transcription and RNA

Transcription and RNA - Transcription and RNA Chapter 21(or...

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“Transcription and RNA” - Chapter 21 (or 19) Replication: DNA ============> copied DNA Transcription: DNA ============> mRNA, rRNA, tRNA, other RNA Translation: mRNA ==============> protein DNA polymerase Ribosome RNA polymerase
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Not all of an organism’s DNA is transcribed into RNA. “gene” = a DNA sequence that is transcribed into RNA by RNA pol. In humans, perhaps 25% of our DNA is transcribed to RNA. Some RNAs that are transcribed include: mRNA (messenger RNA) - codes for protein. tRNA (transfer RNA) - used in protein synthesis rRNA (ribosomal RNA) - component of the ribosome. siRNA (small interfering RNA) - targets mRNA for inactivation.
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Problem - Given the DNA sequence of the human genome, how do we figure out what the amino acid sequences of all of the human proteins are? This is tricky, since the DNA codes for introns and exons. Solution - Use a sample of mature mRNAs, isolated from cytosol. Use the enzyme “ reverse transcriptase ” to make the double- stranded DNA encoded by the mRNAs. (reverse transcriptase is a viral enzyme that does this trick). DNA made in this way is called “ cDNA ”. This is DNA that does not code for introns. Then use standard DNA sequencing methods to sequence the cDNA. A genetic code table can then be used to figure out the amino acid sequences of the proteins that are coded by the DNA.
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cDNA . The DNA sequences that are the result of using the enzyme “reverse transcriptase” to transcribe a mixture of RNAs into their complementary DNAs. Open reading frames (ORFs). ORFs are DNA sequences that potentially may be
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Transcription and RNA - Transcription and RNA Chapter 21(or...

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