Notes- February 4

I. Primary transcripts v. mRNAs
a. mRNA: will be translated to produce protein in eukaryotes, introns must be removed from primary transcript before it can be used as mRNA

nonsense mediated decay:
* new eukaryotic mRNA (just got introns snipped out) still has intron-removal proteins attached to it.
* introns that remain in mRNA likely to contain stop codon
* on 1st round of translation of an mRNA, if tranlation machinery encounters stop codon after it is already read past intron-removal protein, then mRNA destroyed

b. tRNA
- has complementary swatches where it base pairs with itself (gives it a clover shape)
- transfer RNA has a long half-life.
- brings in aa that corresponds to particular mRNA
(lines up correct aa w/ mRNA codon)

"Charged" tRNA: has amino acid attached to it

ii. aminoacyl-tRNA synthases (diff. spelling from textbook)
*attach aa's to back of tRNAs

iii. mutations to tRNA genes (RNA is transcribed off of DNA)
all RNAs are initially transcribed from DNA (includes transfer RNAs & ribosomal RNAs)
so, mutations can occur to tRNA genes (since, like anything else comin from DNA- it can mutate)

What are the consequences of cell mutation to a tRNA gene? ex. recognizes CUC. so anticodon = GAG —> so, if mustated, couldn't pair leucine w/ codon.

concept: generally, just first 2 bases in anticodon + codon must line up for it to work- for the right aa to pair w/ the codon. this is known as the "wobble hypothesis"

mutations to tRNA genes can have pretty dire consequences.
tRNA: lots of duplication of tRAN genes, so usually have lots of copies of tRNA genes.

c. ribosomal RNA = rRNA
main constituent of ribosomes
base-paired w/ itself in large, elaborate structures
—> makes rRNA very stable, long-lived (not easily degraded in the cell like mRNA is)

**extra credit opportunity: go to the global warming speaker today at 11:45 in UPS auditorium. turn in notes or page with a couple sentences about what you learn for 5 e.c. points!

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