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3.5 7.3 Dna Transcription

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3.5 7.3 Dna Transcription

  1. 1. 3.5 & 7.3DNA Transcription<br />IB Biology<br />
  2. 2. Types of RNA:<br />rRNA: ribosomal RNA<br />Major component of ribosomes<br />tRNA: transfer RNA<br />Carries amino acids to mRNA<br />An interpreter in translation<br />mRNA: messenger RNA<br />Encodes genetic info from DNA and convey it to the ribosomes, where the info is translated into amino acid sequences<br />
  3. 3. Transcription<br />The process by which RNA is made from a DNA template<br />Purpose: to read the DNA, one gene at a time. <br />RNA polymerase starts transcription at promoters and end at terminators<br />Complimentary RNA strand is formed<br />RNA is assembled in the 5’ 3’ direction<br />Bubbles open- instead of unzipping<br />
  4. 4. DNA “words”…<br />DNA gives instructions.<br />The instructions are written in a language where words are ALWAYS three base pairs long.<br />Ex: AAT,CCG,GCA,TTC, etc.<br />Each is called a triplet.<br />
  5. 5. Triplets on DNA makeCodons on mRNA<br />Codon- genetic code made of one triplet of bases.<br />Codons are found on mRNA (messenger RNA)<br />
  6. 6. Formation of mRNA<br />Creates a “mirror image” of the triplets found on DNA (except TU)<br />mRNA then travels out of the nucleus and toward a ribosome.<br />The formation of RNA is called transcription<br />
  7. 7. New Enzyme- RNA Polymerase<br />Links together the growing chain of RNA nucleotides during transcription<br />Uses DNA as template<br />Similar to DNA polymerase but only facilitates a reaction on one side of the strand<br />
  8. 8. New Players:<br />Promoter- place on gene where RNA polymerase initially attaches.<br />Terminator- place on gene where transcription ends.<br />
  9. 9. New…the “Middle” Step<br />Transcription - beginning<br />Middle = mRNA processing<br />Translation - end<br />
  10. 10. RNA processing<br />Post-transcriptional<br />Introns- non-coding sequences are removed<br />Exons- coding sequences are spliced together<br />
  11. 11. IB Terms: Sense vs. Antisense strands<br />Sense strand - the “other” strand, not transcribed.<br />Antisense strand -the one mRNA attaches to, and is complimentary to.<br />mRNA is similar to the sense strand, except TU.<br />
  12. 12. The code is universal<br />The same codons are found in all living organisms.<br />

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