Lecture Notes 11

b. Elongation
i. Process by which the RNA strand is actively synthesized by RNA polymerase
ii. RNA strand synthesized by pairing complementary RNA bases with DNA template strand and hooking those bases together with sugar-phosphate backbone
1. Sugar in the backbone is ribose
2. RNA uses Uracil instead of Thymine (U instead of T)
c. Termination (picture in notebook)
i. This is where the RNA enzyme must detach from the DNA strand
ii. The DNA strand folds back over itself forming the ‘hair-pin’ loop – at the end of the strand
iii. RNA polymerase can’t get past the ‘hair-pin’ loop when it reaches it (because can only move along single stranded DNA) so RNA polymerase falls off DNA strand, releasing new single strand RNA
II. Kinds of RNA
a. Messenger RNA (mRNA)
i. Single stranded copy of DNA gene, and is going to be translated into a protein strand (amino acid sequence)
ii. Tend to be very short-lived – only existing in the cell for a few seconds if they aren’t being actively translated or synthesized
b. Transfer RNA (tRNA)
i. Involved a lot in the translation of our mRNA into an amino acid sequence
ii. Has a cloverleaf structure – it is a single stranded RNA that is base paired with itself (picture in notebook)
1. On one side of the tRNA there is an amino acid attached to it
2. On the opposite side of tRNA there is a swatch of just a couple bases that are not bound to anything they just hand out there, so that they can bind with sequences from mRNA (anticodon – the swatch of three bases)
c. Ribosomal RNA (rRNA)
i. Main thing that ribosomes are made out of
ii. Ribosomes are the sight in the cell that do the heavy lifting – translating mRNA into amino acid sequences
iii. Tend to be fairly long-lived
1. Existing in the cell for days to weeks

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