BIOL 400 COMPREHENSIVE EXAM UPDATED QUESTIONS
AND ANSWERS SURE A+
✔✔What happens in pre-mRNA processing in eukaryotes? - ✔✔-cap is added to 5' end
to enable TLN
-Poly-A-tail (50-250 "A" nucleotides) added to 3' end
-RNA is spliced to edit transcript sequence
✔✔Introns vs exons in pre-mRNA processing - ✔✔Introns (intervening sequences) are
cut out
Exons (expressed sequences) are linked together to produce final mRNA transcript
✔✔What's a spliceosome? - ✔✔a structure that splices pre-mRNA
-made of small nuclear RNA (snRNA) & ribozymes
✔✔What does snRNA do in spliceosomes? - ✔✔1) identifies splice signals in intron
sequence by base pairing with them
2) catalyze splicing reactions
✔✔What are ribozymes? - ✔✔RNA molecules capable of acting as enzymes
✔✔What's the point of having introns? - ✔✔They make it easier to evolve new proteins
✔✔What are protein domains? - ✔✔Structural & functional modules within proteins
-their genetic code is often contained in an exon
-allow the creation of proteins
✔✔How do protein domains allow the creation of new proteins? - ✔✔1) By crossover
errors in meiosis
-errors can duplicate and shuffle existing exons
2) By alternative splicing (removing select exons to rearrange order)
-there are different ways to splice a transcript based on cellular conditions
✔✔What happens after mRNA processing? - ✔✔mRNA leaves the nucleus
✔✔Where does translation of mRNA by ribosomes occur? - ✔✔-occurs in the cytoplasm
of all cells
-in eukaryotes also occurs on rough ER & in mitochondrial matrix & chloroplast stroma
✔✔Genetic code - ✔✔-key to translating nucleotide sequences into AAs
-is universal: all organisms share nearly all the code
*allows genes from 1 species to be expressed in another
-made of codons
, ✔✔What are codons? - ✔✔Sequences of 3 nucleotides that encode a specific AA
✔✔Why is the genetic code redundant? - ✔✔More codons than there are AAs
✔✔Ribosome structure - ✔✔2 subunits: large & small
-both made of ribosomal RNAs (rRNA) & proteins
✔✔What are transfer RNAs? (tRNA) - ✔✔RNAs that carry amino acids & bind mRNA
codons
-"transfer" info from mRNA to the new polypeptide
✔✔What do folded tRNAs contain? - ✔✔-attachment site at 1 end for its specific AAs
-an anti-codon
✔✔What's an anti-codon? - ✔✔a region that binds antiparallel* to its AA's specific
mRNA codon using base pairs
✔✔What are AA-tRNA synthetases? - ✔✔Enzymes that attach the correct AA to each
tRNA type
✔✔3 tRNA binding sites on ribosomes and their purposes? - ✔✔A (AA) site: for
incoming AA-tRNA
P (polypeptide) site: for tRNA with growing polypeptide
E (exit) site: exit site for empty tRNA
✔✔3 Stages of Translation and their steps - ✔✔1) Initiation
-small ribosomal subunit & met-tRNA find the start codon (scan 5' to 3')
-met-tRNA binds start codon & sets reading frame
-large ribosomal subunit binds & TLN begins
2) Elongation
-AA-tRNA binds to mRNA A site
-peptide bonds form between AAs on tRNA at A site and tRNA at P site
-chain moves from P site to A site
-A site tRNA moves to P site, empty tRNA in P moves to E site and leaves
-repeats until stop
3) Termination
-stop codon at A site binds release factor
-mRNA & ribosome subunits separate to be used again
✔✔What is the reading frame? - ✔✔a choice of nucleotide triplet groups for translation
- 3 frames possible, but only one is correct
✔✔What is the release factor? - ✔✔the protein that releases the new polypeptide from
tRNA at the P site
AND ANSWERS SURE A+
✔✔What happens in pre-mRNA processing in eukaryotes? - ✔✔-cap is added to 5' end
to enable TLN
-Poly-A-tail (50-250 "A" nucleotides) added to 3' end
-RNA is spliced to edit transcript sequence
✔✔Introns vs exons in pre-mRNA processing - ✔✔Introns (intervening sequences) are
cut out
Exons (expressed sequences) are linked together to produce final mRNA transcript
✔✔What's a spliceosome? - ✔✔a structure that splices pre-mRNA
-made of small nuclear RNA (snRNA) & ribozymes
✔✔What does snRNA do in spliceosomes? - ✔✔1) identifies splice signals in intron
sequence by base pairing with them
2) catalyze splicing reactions
✔✔What are ribozymes? - ✔✔RNA molecules capable of acting as enzymes
✔✔What's the point of having introns? - ✔✔They make it easier to evolve new proteins
✔✔What are protein domains? - ✔✔Structural & functional modules within proteins
-their genetic code is often contained in an exon
-allow the creation of proteins
✔✔How do protein domains allow the creation of new proteins? - ✔✔1) By crossover
errors in meiosis
-errors can duplicate and shuffle existing exons
2) By alternative splicing (removing select exons to rearrange order)
-there are different ways to splice a transcript based on cellular conditions
✔✔What happens after mRNA processing? - ✔✔mRNA leaves the nucleus
✔✔Where does translation of mRNA by ribosomes occur? - ✔✔-occurs in the cytoplasm
of all cells
-in eukaryotes also occurs on rough ER & in mitochondrial matrix & chloroplast stroma
✔✔Genetic code - ✔✔-key to translating nucleotide sequences into AAs
-is universal: all organisms share nearly all the code
*allows genes from 1 species to be expressed in another
-made of codons
, ✔✔What are codons? - ✔✔Sequences of 3 nucleotides that encode a specific AA
✔✔Why is the genetic code redundant? - ✔✔More codons than there are AAs
✔✔Ribosome structure - ✔✔2 subunits: large & small
-both made of ribosomal RNAs (rRNA) & proteins
✔✔What are transfer RNAs? (tRNA) - ✔✔RNAs that carry amino acids & bind mRNA
codons
-"transfer" info from mRNA to the new polypeptide
✔✔What do folded tRNAs contain? - ✔✔-attachment site at 1 end for its specific AAs
-an anti-codon
✔✔What's an anti-codon? - ✔✔a region that binds antiparallel* to its AA's specific
mRNA codon using base pairs
✔✔What are AA-tRNA synthetases? - ✔✔Enzymes that attach the correct AA to each
tRNA type
✔✔3 tRNA binding sites on ribosomes and their purposes? - ✔✔A (AA) site: for
incoming AA-tRNA
P (polypeptide) site: for tRNA with growing polypeptide
E (exit) site: exit site for empty tRNA
✔✔3 Stages of Translation and their steps - ✔✔1) Initiation
-small ribosomal subunit & met-tRNA find the start codon (scan 5' to 3')
-met-tRNA binds start codon & sets reading frame
-large ribosomal subunit binds & TLN begins
2) Elongation
-AA-tRNA binds to mRNA A site
-peptide bonds form between AAs on tRNA at A site and tRNA at P site
-chain moves from P site to A site
-A site tRNA moves to P site, empty tRNA in P moves to E site and leaves
-repeats until stop
3) Termination
-stop codon at A site binds release factor
-mRNA & ribosome subunits separate to be used again
✔✔What is the reading frame? - ✔✔a choice of nucleotide triplet groups for translation
- 3 frames possible, but only one is correct
✔✔What is the release factor? - ✔✔the protein that releases the new polypeptide from
tRNA at the P site
