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BIOL 105
Dr. Corl
October 25, 2013
The Central
Dogma
• DNA codes for
RNA, which codes
for protein.
The Central Dogma
• Transcription is a process in which:
– The sequence of bases in a particular stretch of
DNA (a gene) specifies the sequence of bases in
an mRNA molecule.

• Translation is a process in which:
– A particular mRNA molecule then specifies the
exact sequence of amino acids in a protein.

• Thus, genes ultimately code for proteins.
Transcription in Bacteria
• In transcription:
– Instructions stored in DNA are “transcribed”
through the synthesis of an mRNA transcript.

• Transcription performed by RNA polymerase.
• Three phases of transcription:
– Initiation, elongation, and termination.
Transcription in Bacteria

• mRNA transcript is synthesized by RNA polymerase
in the 5’ to 3’ direction.
• Template strand:
– DNA strand that is read (transcribed) by RNA polymerase.

• Non-template strand:
– DNA strand that is not read by RNA polymerase.
Transcription in Bacteria

• “Activated” complementary ribonucleotide
monomers are added on via condensation
reactions, resulting in phosphodiester bonds.
Bacterial RNA Polymerase

• A holoenzyme:
– An enzyme made up of a core enzyme and other
required proteins.
– Bacterial RNA polymerase is made up of a core
enzyme and a regulatory subunit, sigma.
Bacterial RNA Polymerase

• Core enzyme:
– Contains the active site where mRNA is synthesized.

• Sigma:
– A regulatory factor required for initiation of transcription.
– Tells core enzyme where in a DNA sequence to start transcription.
Transcription: Initiation
• Transcription initiation begins at specific
sequences of DNA called promoters.
• Two important bacterial promoter regions :
– Named the -10 box and the -35 box.
– Sigma recognizes these promoter regions and
brings the RNA polymerase core enzyme to the
promoter to initiate transcription.
Transcription: Initiation

Core enzyme

• 1.) sigma binds to specific promoter
regions of DNA (-35 box and -10 box).
Transcription: Initiation

• 2.) DNA double helix is opened and the
template strand of DNA is threaded through
RNA polymerase core enzyme active site.
mRNA synthesis begins.
Transcription: Initiation

• 3.) Initiation is complete.
Sigma dissociates from core enzyme.
mRNA synthesis (transcription) continues.
Transcription: Elongation

• Core enzymes of RNA polymerase moves along
the DNA template and continues to catalyze the
addition of complementary ribonucleotides to the
growing mRNA transcript.
Transcription: Termination
• RNA polymerase
encounters a
termination signal
within the DNA
template, which
codes for RNA
forming a hairpin
loop structure.
• Hairpin causes RNA
polymerase to
separate from RNA
transcript, ending
transcription.
Bacterial Transcription: Summary
• Initiation:
– Sigma brings RNA polymerase holoenzyme to
promoter region of DNA.
– DNA helix is opened and transcription begins.
– Sigma releases and transcription continues.

• Elongation:
– Complementary ribonucleotides are added to the
growing mRNA transcript as specified by the DNA
template strand.

• Termination:
– RNA polymerase reaches a termination signal in
the DNA template.
– mRNA forms a hairpin loop.
– mRNA dissociates from RNA polymerase.
Transcription in Eukaryotes
• Overall similar to bacterial transcription.
• Some differences include:
– Basal transcription factors:
• Proteins that bind DNA promoters independant of
RNA polymerase.
• RNA polymerase then binds to basal transcription
factors and transcription begins.

– Greater diversity and complexity of promoters:
• Many promoters include a TATA box sequence.
Transcription in Eukaryotes
• Three types of RNA polymerase:
– RNA polymerase II:
• Catalyzes transcription of genes that code for
proteins, forming mRNA.

– RNA polymerase I and RNA polymerase III:
• Catalyze transcription of non-protein coding
genes (e.g. genes coding for ribosomal rRNAs
and genes coding for transfer tRNAs).
Eukaryotic mRNA Processing

Exon 1

Intron 1
Intron 2
Exon 2

Exon 3

• After transcription but before translation, specific
regions of the primary RNA transcript are spliced
out (cut out) and degraded during RNA processing.
• The term intron can be used in two ways:
– A stretch of RNA that does get spliced out and will NOT
be a part of the final mature spliced RNA transcript.
– A stretch of DNA that codes for an RNA intron.
Eukaryotic mRNA Processing

Exon 1

Intron 1
Intron 2
Exon 2

Exon 3

• After transcription but before translation, specific
regions of the primary RNA transcript are spliced
out (cut out) and degraded during RNA processing.
• The term exon can be used in two ways:
– A stretch of RNA that does NOT get spliced out and will
be a part of the final mature spliced RNA transcript.
– A stretch of DNA that codes for an RNA exon.
Eukaryotic mRNA Processing

-Intron regions of the primary mRNA transcript are
spliced out by small nuclear ribonucleoproteins
(snRNPs), which assemble to form a spliceosome
(a ribozyme).
Eukaryotic mRNA Processing

• Intron regions of the primary mRNA transcript
are spliced out by snRNPs, which assemble to
form a spliceosome. (occurs within nucleus)
Eukaryotic mRNA Processing

• Additionally, a 5’ cap is added to the
very 5’ end of the mRNA transcript:
– 5’ cap serves as recognition signal for the
translation machinery of the cell.
Eukaryotic mRNA Processing

• Finally, a poly (A) tail is added to the
very 3’ end of the mRNA transcript:
– Extends the life of the mRNA by protecting
it from enzymatic degradation.
Transcription: Summary

• Note the similarities and differences between
bacterial vs. eukaryotic transcription!
• Eukaryotic transcription tends to be more complex.
Translation
• In translation:
– The sequence of bases in mRNA is
converted (“translated”) to an amino acid
sequence of a protein.

• Ribosomes catalyze the translation of
mRNA sequence into protein.
Translation in Bacteria

• In bacteria, transcription and translation can
occur simultaneously:
– Ribosomes begin translating an mRNA even before
RNA polymerase has finished synthesizing it!
Translation in Bacteria

• In bacteria, transcription and translation can
occur simultaneously:
– Ribosomes begin translating an mRNA even before
RNA polymerase has finished synthesizing it!
Translation in
Eukaryotes

• Transcription and translation are separated:
– Transcription takes place in the nucleus.
– Translation takes place in the cytoplasm.
Translation

• How do mRNA codons interact with amino acids?
Translation

• Adapter molecules:
– Small RNAs called transfer RNA (tRNA)
– Hold amino acids in place and interact directly and
specifically with a codon in mRNA.
Transfer RNA (tRNA)
• Different tRNAs covalently link to
specific amino acids, forming aminoacyl
tRNAs.
• Aminoacyl tRNA synthesizes:
– Enzymes which catalyze the addition of
amino acids to tRNAs.
Loading Amino Acid Onto tRNA
Step 1

Step 3

Step 2
Step 4

• Amino acid binds to its specific aminoacyl tRNA
sythnetase, which then covelantly attaches the
amino acid onto a specific tRNA.
Loading Amino Acid Onto tRNA
Step 1

Step 3

Step 2
Step 4

• Is ATP expended in this process? Yes!
• Aminoacyl tRNA = “CHARGED” tRNA
Aminoacyl tRNA

• Aminoacyl tRNAs then travel to ribosomes and
transfer amino acids to growing polypeptides.
• Each tRNA carries a specific amino acid that can
be transferred to protein.
Transfer RNA Structure

• tRNA secondary
structure resembles a
“cloverleaf.”
tRNA Secondary Structure

• 3’ end of tRNA: binding site for amino acids.
• Triplet loop at opposite end (anticodon):
– Interacts with complementary codon on mRNA.
tRNA Tertiary Structure

• tRNA has an “L-shaped” tertiary structure.
• Each tRNA has a distinct anticodon and attached
amino acid.
Wobble Hypothesis
• There are 61 different codons but only
40 different tRNAs.
• Explained by “wobble hypothesis”:
– The anticodon of certain tRNAs can bind
successfully to a codon whose third
position requires nonstandard base pairing.
– Allows one tRNA to be able to base pair
with more than one type of codon.
Ribosomes
• Composed of both ribosomal protein and
ribosomal RNA (rRNA).
• Can be separated into two subunits:
– Large subunit and small subunit.

• There are three sites within a ribosome that
tRNAs can reside:
– The A site, the P site, and the E site.
Ribosome: Structure
Large subunit
E

P

A

Small subunit

• Large subunit and small subunit.
• Three sites where tRNAs can reside: A, P and E.
Ribosome: Structure and Function

• Each tRNA binds at its anticodon to its corresponding
mRNA codon and transfers its amino acid to a
growing polypeptide chain.
Phases of Protein Synthesis
• initiation:
– Ribosomal subunits and mRNA assemble.
– Translation begins at the AUG start codon.
• elongation:
– Amino acids are transferred one by one from
aminoacyl tRNAs to a growing polypeptide chain.
• termination:
– Stop codon in mRNA causes protein to be
released from ribosome.
– Ribosomal subunits separate from mRNA and
from one another.
Initiation: Step 1

• mRNA is targeted to the ribosome:
– Ribosome binding site on mRNA binds to
complementary sequence on small subunit of ribosome,
with the help of proteins called initiation factors.
Initiation: Step 2

• Translation begins at the AUG start codon:
– Initiator aminoacyl tRNA, bringing in the first amino acid,
binds to the mRNA’s start codon, AUG.
Initiation: Step 3

• LARGE subunit of ribosome binds, placing initiator
aminoacyl tRNA in the P-site.
Elongation: Step 1

• Incoming aminoacyl tRNA binds to the codon in
theA site via complementary base pairing
between anticodon and codon.
Elongation: Step 2

• The amino acid in the P site:
– Breaks the bond with its tRNA.
– Forms a peptide bond with the amino acid in the A site.
Elongation: Step 3

• Translocation:
– Ribosome moves down to the next codon on mRNA.
– Results in tRNAs being shifted over one spot:
• tRNA in P site moves to E site.
• tRNA in A site moves to P site.
Another Elongation Cycle

• 1.) Incoming aminoacyl tRNA enters into the __ site.
• 2.) peptide bond formation.
– rRNA acts as a catalyst: ribozyme

• 3.) Translocation.
Polyribosome

• multiple ribosomes assembled along a single
mRNA, synthesizing proteins from the same
mRNA at the same time.
Termination: Step 1

• Occurs when a stop codon is revealed in the A site.
• A protein called a release factor enters the A site
and promotes the hydrolysis of the bond linking the
tRNA in the P-site with its polypeptide.
Termination: Steps 2 and 3

• Hydrolysis reaction (cleavage of bond between
tRNA and polypeptide) frees the polypeptide
• Ribosomal subunits, mRNA, tRNAs, and
polypeptide all _________ from one another.
Post-Translational Modifications
• Many proteins are modified after
translation is complete:
– Many proteins fold with the help of
molecular chaperones.
– Proteins can be modified by attachment of
sugars (glycosylation) in the rough ER
and/or Golgi.
– Proteins can be phosphorylated or
dephosphorylated, modifying their activity.
Mutations
• Mutation:
– Any permanent change in an organism’s DNA.
– Changes the genotype (DNA) of the cell.
• This may then result in a change in mRNA transcript
sequence, resulting in:
– Change in sequence of amino acids of the translated protein.
Point Mutations

• A single base pair change, often as a
result of errors in DNA replication.
• Can affect the primary structure of the
polypeptide that is ultimately translated.
Point Mutations

• missense mutation:
– Point mutation in a gene’s DNA sequence that
ultimately results in a single amino acid change in the
protein encoded by that gene.
– Can often be deleterious:
• Reduces the individual’s fitness.
Point Mutations

• silent mutation:
– Does not change amino acid sequence.

• nonsense mutation:
– Results in an early stop codon: shortened protein.

• frameshift mutation:
– Addition or deletion of a nucleotide causes entire reading
frame to be shifted.
Chromosome-Level Mutations

• Chromosome INVERSION and translocation:
– Can result in altered patterns of gene expression.
Summary
• Transcription:
– Bacterial transcription
– Eukaryotic transcription

• Translation:
– Ribosomes
– tRNA and aminoacyl tRNA
– Ribosomal protein synthesis

• Mutations:
– Point mutations
– Chromosomal mutations
Review Questions on
Transcription
• Contrast the functions of sigma versus the
core enzyme of bacterial RNA polymerase.
• What events occur during transcription
initiation? Elongation? Termination?
• How does eukaryotic transcription differ from
bacterial transcription?
• What types of post-transcriptional processing
occur in eukaryotes? What is splicing?
Review Questions on
Translation
• What is the function of tRNA? mRNA? rRNA?
• What events occur during the three major phases of
translation?
• What are the A, P, and E sites of a ribosome?
• What are the differences between silent, missense,
nonsense, and frameshift mutations?

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27 28 105 fa13 transcription and translation skel

  • 1. Transcription and Translation BIOL 105 Dr. Corl October 25, 2013
  • 2. The Central Dogma • DNA codes for RNA, which codes for protein.
  • 3. The Central Dogma • Transcription is a process in which: – The sequence of bases in a particular stretch of DNA (a gene) specifies the sequence of bases in an mRNA molecule. • Translation is a process in which: – A particular mRNA molecule then specifies the exact sequence of amino acids in a protein. • Thus, genes ultimately code for proteins.
  • 4. Transcription in Bacteria • In transcription: – Instructions stored in DNA are “transcribed” through the synthesis of an mRNA transcript. • Transcription performed by RNA polymerase. • Three phases of transcription: – Initiation, elongation, and termination.
  • 5. Transcription in Bacteria • mRNA transcript is synthesized by RNA polymerase in the 5’ to 3’ direction. • Template strand: – DNA strand that is read (transcribed) by RNA polymerase. • Non-template strand: – DNA strand that is not read by RNA polymerase.
  • 6. Transcription in Bacteria • “Activated” complementary ribonucleotide monomers are added on via condensation reactions, resulting in phosphodiester bonds.
  • 7. Bacterial RNA Polymerase • A holoenzyme: – An enzyme made up of a core enzyme and other required proteins. – Bacterial RNA polymerase is made up of a core enzyme and a regulatory subunit, sigma.
  • 8. Bacterial RNA Polymerase • Core enzyme: – Contains the active site where mRNA is synthesized. • Sigma: – A regulatory factor required for initiation of transcription. – Tells core enzyme where in a DNA sequence to start transcription.
  • 9. Transcription: Initiation • Transcription initiation begins at specific sequences of DNA called promoters. • Two important bacterial promoter regions : – Named the -10 box and the -35 box. – Sigma recognizes these promoter regions and brings the RNA polymerase core enzyme to the promoter to initiate transcription.
  • 10. Transcription: Initiation Core enzyme • 1.) sigma binds to specific promoter regions of DNA (-35 box and -10 box).
  • 11. Transcription: Initiation • 2.) DNA double helix is opened and the template strand of DNA is threaded through RNA polymerase core enzyme active site. mRNA synthesis begins.
  • 12. Transcription: Initiation • 3.) Initiation is complete. Sigma dissociates from core enzyme. mRNA synthesis (transcription) continues.
  • 13. Transcription: Elongation • Core enzymes of RNA polymerase moves along the DNA template and continues to catalyze the addition of complementary ribonucleotides to the growing mRNA transcript.
  • 14. Transcription: Termination • RNA polymerase encounters a termination signal within the DNA template, which codes for RNA forming a hairpin loop structure. • Hairpin causes RNA polymerase to separate from RNA transcript, ending transcription.
  • 15. Bacterial Transcription: Summary • Initiation: – Sigma brings RNA polymerase holoenzyme to promoter region of DNA. – DNA helix is opened and transcription begins. – Sigma releases and transcription continues. • Elongation: – Complementary ribonucleotides are added to the growing mRNA transcript as specified by the DNA template strand. • Termination: – RNA polymerase reaches a termination signal in the DNA template. – mRNA forms a hairpin loop. – mRNA dissociates from RNA polymerase.
  • 16. Transcription in Eukaryotes • Overall similar to bacterial transcription. • Some differences include: – Basal transcription factors: • Proteins that bind DNA promoters independant of RNA polymerase. • RNA polymerase then binds to basal transcription factors and transcription begins. – Greater diversity and complexity of promoters: • Many promoters include a TATA box sequence.
  • 17. Transcription in Eukaryotes • Three types of RNA polymerase: – RNA polymerase II: • Catalyzes transcription of genes that code for proteins, forming mRNA. – RNA polymerase I and RNA polymerase III: • Catalyze transcription of non-protein coding genes (e.g. genes coding for ribosomal rRNAs and genes coding for transfer tRNAs).
  • 18. Eukaryotic mRNA Processing Exon 1 Intron 1 Intron 2 Exon 2 Exon 3 • After transcription but before translation, specific regions of the primary RNA transcript are spliced out (cut out) and degraded during RNA processing. • The term intron can be used in two ways: – A stretch of RNA that does get spliced out and will NOT be a part of the final mature spliced RNA transcript. – A stretch of DNA that codes for an RNA intron.
  • 19. Eukaryotic mRNA Processing Exon 1 Intron 1 Intron 2 Exon 2 Exon 3 • After transcription but before translation, specific regions of the primary RNA transcript are spliced out (cut out) and degraded during RNA processing. • The term exon can be used in two ways: – A stretch of RNA that does NOT get spliced out and will be a part of the final mature spliced RNA transcript. – A stretch of DNA that codes for an RNA exon.
  • 20. Eukaryotic mRNA Processing -Intron regions of the primary mRNA transcript are spliced out by small nuclear ribonucleoproteins (snRNPs), which assemble to form a spliceosome (a ribozyme).
  • 21. Eukaryotic mRNA Processing • Intron regions of the primary mRNA transcript are spliced out by snRNPs, which assemble to form a spliceosome. (occurs within nucleus)
  • 22. Eukaryotic mRNA Processing • Additionally, a 5’ cap is added to the very 5’ end of the mRNA transcript: – 5’ cap serves as recognition signal for the translation machinery of the cell.
  • 23. Eukaryotic mRNA Processing • Finally, a poly (A) tail is added to the very 3’ end of the mRNA transcript: – Extends the life of the mRNA by protecting it from enzymatic degradation.
  • 24. Transcription: Summary • Note the similarities and differences between bacterial vs. eukaryotic transcription! • Eukaryotic transcription tends to be more complex.
  • 25. Translation • In translation: – The sequence of bases in mRNA is converted (“translated”) to an amino acid sequence of a protein. • Ribosomes catalyze the translation of mRNA sequence into protein.
  • 26. Translation in Bacteria • In bacteria, transcription and translation can occur simultaneously: – Ribosomes begin translating an mRNA even before RNA polymerase has finished synthesizing it!
  • 27. Translation in Bacteria • In bacteria, transcription and translation can occur simultaneously: – Ribosomes begin translating an mRNA even before RNA polymerase has finished synthesizing it!
  • 28. Translation in Eukaryotes • Transcription and translation are separated: – Transcription takes place in the nucleus. – Translation takes place in the cytoplasm.
  • 29. Translation • How do mRNA codons interact with amino acids?
  • 30. Translation • Adapter molecules: – Small RNAs called transfer RNA (tRNA) – Hold amino acids in place and interact directly and specifically with a codon in mRNA.
  • 31. Transfer RNA (tRNA) • Different tRNAs covalently link to specific amino acids, forming aminoacyl tRNAs. • Aminoacyl tRNA synthesizes: – Enzymes which catalyze the addition of amino acids to tRNAs.
  • 32. Loading Amino Acid Onto tRNA Step 1 Step 3 Step 2 Step 4 • Amino acid binds to its specific aminoacyl tRNA sythnetase, which then covelantly attaches the amino acid onto a specific tRNA.
  • 33. Loading Amino Acid Onto tRNA Step 1 Step 3 Step 2 Step 4 • Is ATP expended in this process? Yes! • Aminoacyl tRNA = “CHARGED” tRNA
  • 34. Aminoacyl tRNA • Aminoacyl tRNAs then travel to ribosomes and transfer amino acids to growing polypeptides. • Each tRNA carries a specific amino acid that can be transferred to protein.
  • 35. Transfer RNA Structure • tRNA secondary structure resembles a “cloverleaf.”
  • 36. tRNA Secondary Structure • 3’ end of tRNA: binding site for amino acids. • Triplet loop at opposite end (anticodon): – Interacts with complementary codon on mRNA.
  • 37. tRNA Tertiary Structure • tRNA has an “L-shaped” tertiary structure. • Each tRNA has a distinct anticodon and attached amino acid.
  • 38. Wobble Hypothesis • There are 61 different codons but only 40 different tRNAs. • Explained by “wobble hypothesis”: – The anticodon of certain tRNAs can bind successfully to a codon whose third position requires nonstandard base pairing. – Allows one tRNA to be able to base pair with more than one type of codon.
  • 39. Ribosomes • Composed of both ribosomal protein and ribosomal RNA (rRNA). • Can be separated into two subunits: – Large subunit and small subunit. • There are three sites within a ribosome that tRNAs can reside: – The A site, the P site, and the E site.
  • 40. Ribosome: Structure Large subunit E P A Small subunit • Large subunit and small subunit. • Three sites where tRNAs can reside: A, P and E.
  • 41. Ribosome: Structure and Function • Each tRNA binds at its anticodon to its corresponding mRNA codon and transfers its amino acid to a growing polypeptide chain.
  • 42. Phases of Protein Synthesis • initiation: – Ribosomal subunits and mRNA assemble. – Translation begins at the AUG start codon. • elongation: – Amino acids are transferred one by one from aminoacyl tRNAs to a growing polypeptide chain. • termination: – Stop codon in mRNA causes protein to be released from ribosome. – Ribosomal subunits separate from mRNA and from one another.
  • 43. Initiation: Step 1 • mRNA is targeted to the ribosome: – Ribosome binding site on mRNA binds to complementary sequence on small subunit of ribosome, with the help of proteins called initiation factors.
  • 44. Initiation: Step 2 • Translation begins at the AUG start codon: – Initiator aminoacyl tRNA, bringing in the first amino acid, binds to the mRNA’s start codon, AUG.
  • 45. Initiation: Step 3 • LARGE subunit of ribosome binds, placing initiator aminoacyl tRNA in the P-site.
  • 46. Elongation: Step 1 • Incoming aminoacyl tRNA binds to the codon in theA site via complementary base pairing between anticodon and codon.
  • 47. Elongation: Step 2 • The amino acid in the P site: – Breaks the bond with its tRNA. – Forms a peptide bond with the amino acid in the A site.
  • 48. Elongation: Step 3 • Translocation: – Ribosome moves down to the next codon on mRNA. – Results in tRNAs being shifted over one spot: • tRNA in P site moves to E site. • tRNA in A site moves to P site.
  • 49. Another Elongation Cycle • 1.) Incoming aminoacyl tRNA enters into the __ site. • 2.) peptide bond formation. – rRNA acts as a catalyst: ribozyme • 3.) Translocation.
  • 50. Polyribosome • multiple ribosomes assembled along a single mRNA, synthesizing proteins from the same mRNA at the same time.
  • 51. Termination: Step 1 • Occurs when a stop codon is revealed in the A site. • A protein called a release factor enters the A site and promotes the hydrolysis of the bond linking the tRNA in the P-site with its polypeptide.
  • 52. Termination: Steps 2 and 3 • Hydrolysis reaction (cleavage of bond between tRNA and polypeptide) frees the polypeptide • Ribosomal subunits, mRNA, tRNAs, and polypeptide all _________ from one another.
  • 53. Post-Translational Modifications • Many proteins are modified after translation is complete: – Many proteins fold with the help of molecular chaperones. – Proteins can be modified by attachment of sugars (glycosylation) in the rough ER and/or Golgi. – Proteins can be phosphorylated or dephosphorylated, modifying their activity.
  • 54. Mutations • Mutation: – Any permanent change in an organism’s DNA. – Changes the genotype (DNA) of the cell. • This may then result in a change in mRNA transcript sequence, resulting in: – Change in sequence of amino acids of the translated protein.
  • 55. Point Mutations • A single base pair change, often as a result of errors in DNA replication. • Can affect the primary structure of the polypeptide that is ultimately translated.
  • 56. Point Mutations • missense mutation: – Point mutation in a gene’s DNA sequence that ultimately results in a single amino acid change in the protein encoded by that gene. – Can often be deleterious: • Reduces the individual’s fitness.
  • 57. Point Mutations • silent mutation: – Does not change amino acid sequence. • nonsense mutation: – Results in an early stop codon: shortened protein. • frameshift mutation: – Addition or deletion of a nucleotide causes entire reading frame to be shifted.
  • 58. Chromosome-Level Mutations • Chromosome INVERSION and translocation: – Can result in altered patterns of gene expression.
  • 59. Summary • Transcription: – Bacterial transcription – Eukaryotic transcription • Translation: – Ribosomes – tRNA and aminoacyl tRNA – Ribosomal protein synthesis • Mutations: – Point mutations – Chromosomal mutations
  • 60. Review Questions on Transcription • Contrast the functions of sigma versus the core enzyme of bacterial RNA polymerase. • What events occur during transcription initiation? Elongation? Termination? • How does eukaryotic transcription differ from bacterial transcription? • What types of post-transcriptional processing occur in eukaryotes? What is splicing?
  • 61. Review Questions on Translation • What is the function of tRNA? mRNA? rRNA? • What events occur during the three major phases of translation? • What are the A, P, and E sites of a ribosome? • What are the differences between silent, missense, nonsense, and frameshift mutations?

Editor's Notes

  1. Don’t memorize stuff on the right side
  2. (Trna)AAG----(MRNA)-uuc and uuu
  3. A-AMINOACIL tRNA site P-PEPtidyl TRNA site E-exit
  4. MISSING SLIDE FILL IN = POLYPLOIDY, ANEURPLOIDY