November 7 (continued from 11-3 handout)

ii. Elongation
1. RNA polymerase reaches gene beginning, starts bringing in RNA bases complementary to ssDNA sequence, hooks bases into chain w/ sugar-phosphate backbone
a. Sugar-phosphate backbone has ribose-phosphate
b. RNA uses uracil, not thymine
iii. Termination
1. At end of DNA gene a hair-pin loop forms
2. RNA polymerase can’t pass the hair-pin loop and falls off the DNA and then releases RNA polymerase
2. Kinds of RNA
a. Messenger RNA (mRNA): serves as the template for proteins
i. Can be seen as a set of codons (3 base long set of RNA bases that codes fora particular amino acid)
ii. Short lived; dissolves in ~30 seconds if not actively being translated
iii. Come from DNA genes from all the previous steps in transcription but never get translated into proteins
b. Transfer RNA (tRNA): clover-leaf shaped w/ anticodon loop that is complementary to mRNA codon at the top
i. Charged + RNA has correct amino acid for mRNA complementary codon attached to the opposite side of the anticodon loop
ii. Come from other genes but do not get translated into proteins
iii. Long lived
c. Ribosomal RNA (rRNA): main component of ribosomes (80% of ribosomes by weight)
i. Ribosomes translate mRNA to protein
ii. Long lived
3. Overview of Translation
a. DNA genemRNA transcriptionamino acid chain
i. mRNA has 3-base long codons that are complementary to anticodons on tRNAs
1. 20 amino acids and 3 bases/codon an d 4 bases= 43= 64 possible codons
b. Codon: 3 mRNA nucleotide sequence that codes for specific amino acids

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License