November 9th notes

2. Elongation: RNA strand synthesized by pairing complementary RNA bases with DNA template strand and hooking those bases together with sugar-phosphate backbone (RNA  sugar = ribose)
3. Termination (where DNA folds back on self is called a hairpin loop) (DNA strand that’s folded back on itself because complementary to self = “Hairpin loop”) RNA polymerase reaches hairpin loop, can’t get past (because RNA polymerase can only move alone SS (single stranded) DNA) So RNA polymerase falls off DNA strand, releasing new SS RNA
II. Kinds of RNA
a) mRNA – messenger RNA – single stranded RNA copy of DNA gene, will be translated to amino acid sequence (short lived only second if not being actively transcribed or translated)
b) tRNA – transfer RNA – going to be involved a lot in the translation of mRNA in the amino acid chain sequence (involved in translation of mRNA to amino acid chain) “Cloverleaf” structure (tRNA is also single stranded (SS) RNA but that’s base-paired with itself) (one side that has amino acid attached) (other side has ACG attached to it that can base air with sequence on the messenger RNA) (3 bases that can pair with sets of 3 bases on mRNA) (long lived – days or weeks)
c) rRNA – ribosomal RNA – main thing that ribosomes are made out of. Ribosomes translate mRNA into amino acid sequences (long lived – days or weeks)
III. Overview of Translation:
a) DNA gene  mRNA transcript  amino acid chain
b) Codon – 3 mRNA nucleotide sequence (base–long) that codes for specific(particular) amino acid
1. Redundant codons – Why? 64 possible codons, 20 amino acids. Have more than 1 codon per amino acid.
2. Know how to use table of codons, like the one attached
c) Ribsomes bind (attaches) to mRNA at the Shine–Dalgarno sequence – a specific series of bases on mRNA that are complementary to sequence of bases in rRNA
d) AUG = start codon; also, methionine (Ribosome moves 1 base a t a time down mRNA until it reaches AUG – this defines “Reading Frame” of mRNA)
e) tRNAs (clover-leaf shaped with anti-codon on one side, amino acid on other) (other rRNA brings in and RNA’s and Matches them with codons on mRNA) bearing amino acids brought in by ribosome, matched to codons
1. tRNA has anticodon that is complementary to mRNA codon
f) amino acids linked into a chain by ribosome (rRNA forms bond between amino acids that are adjacent to each other) (tRNA is detached from amino acid
g) at stop codon (UAA, UAG, or UGA), ribosome releases mRNA and amino acid chain (because no tRNA with anticodon complementary to stop codon, rRNA pauses at stop codon – proteins called release factors bind to stop codon – bind with stop codons, catalyze release of amino acid chain from ribosome from mRNA)

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