november 18 notes

November 18, 2009—notes
Discussion on transcription
prfB codes for Release Factor 2
Release Factor 2: recognizes the stop codons UAA & UGA
What will happen to translation of this mRNA if:
There’s a lot of RF2 protein available?
There’s very little/no RF2 protein available?
a) If there is a lot of RF2 translation will stop at the stop codon
b) If there is very little/none then the translation will continue right on past the stop codon, and there will eventually be a shift
1) Genetic material of viruses:
a) Can be DNA or Rna
b) Variety of viral genome sizes:
• Smallpox- DNA genome that is about 300,000 base pairs in length
Has 300-1500 genes coding for different proteins
• Polio- RNA genome that is about 3,000 base pairs in length
Has 3-15 genes coding for different proteins
 Generally 1 gene is about 1,000 base pairs in length
c) Viroid: self-replicating double-stranded DNA circle
2) Protein coat
a) Capsid: made of capsomeres
b) Capsomeres: small, Repeating protein units that make up capsid
• Genes for capsomeres in viral genomes
3) Envelope viruses: many, though not all eukaryotic-infecting viruses have a phospholipid bilayer membrane
4) Glycoproteins: attach virus to host cell
5) Attach membrane to the capsid in envelope viruses

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