protein synthesis transcription and translation ap biology unit 2
TRANSCRIPT
![Page 1: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/1.jpg)
Protein SynthesisProtein Synthesis
Transcription and Translation
AP BiologyUnit 2
![Page 2: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/2.jpg)
Flow of Genetic Information
• All living organisms use DNA to synthesize RNA to make proteins
• Same two-step process:Transcription
Translation • Some antibiotics inhibit
protein synthesis in bacteria.– Ex. Neomycin (the antibiotic
in Neosporin) interferes with the process of translation)
![Page 3: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/3.jpg)
Genes and Chromosomes• DNA is organized into
chromosomes– Humans have 46 chromosomes in
each cell.
• Genes are “coding” regions of DNA– Each gene is the code for how to
make a specific protein. • Human chromosomes are made up
of – DNA– Histone proteins that DNA is
wound around
![Page 4: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/4.jpg)
Structure of DNA
• The carbons in the 5C sugar each have a number– Start to the right of the oxygen
and go around clockwise PO
phosphate
Sugar Base
1
23
4
5
• This gives the nucleotide 2 distinct ends
–5’ end (closer to carbon 5) –3’ end (closer to carbon 3)
![Page 5: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/5.jpg)
A way to remember it: Human Nucleotide
4 C5 C
3C C 2
C 1
Phosphate
Base
![Page 6: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/6.jpg)
Nucleic Acid Structure
• DNA is double stranded
• Hydrogen bonds between bases– A pairs with T– C pairs with G
Image taken without permission from http://bcs.whfreeman.com/thelifewire
• The strands are antiparallel–One strand runs 5’-3’–The other runs 3’-5’
![Page 7: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/7.jpg)
Question…
• Why can’t the DNA strands be parallel (both running 5’-3’)?– This wouldn’t allow the bases to be near each
other to hydrogen bond.
![Page 8: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/8.jpg)
Transcription
• DNA is transcribed into 3 kinds of RNA– mRNA = messenger RNA (the RNA code used
to make protein)– tRNA = transfer RNA (participates in
translation)– rRNA = ribosomal RNA (part of ribosomes)
• RNA Polymerase is the enzyme that transcribes the DNA into RNA
![Page 9: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/9.jpg)
Initiation• How transcription starts• RNA Polymerase recognizes a
promoter sequence on the DNA• RNA Polymerase binds to the
promoter• DNA is unwound to start
transcription– What kind of bonds are being
broken to unwind/separate the strands of DNA?
– Hydrogen bonds
![Page 10: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/10.jpg)
Promoter Sequences
• In prokaryotes, RNA Polymerase must find these sequences:
• + 1 is the first base in the RNA (where the actual transcription of DNA starts from)
5’ 3’ 5’ 3’
![Page 11: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/11.jpg)
Eukaryotic Promoter Sequences
• In eukaryotes, the RNA polymerase must find the following sequences:
• Eukaryotic genes can also have enhancer sequences to help RNA polymerase bind– We’ll talk about these a little later– don’t worry
about them right now
![Page 12: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/12.jpg)
What do you think this diagram shows about transcription?
Bases changed
to…
![Page 13: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/13.jpg)
Promoters
• In order for RNA Polymerase to recognize it, the promoter sequences– Must be the correct sequence of bases (small
changes OK)– Must be correctly spaced apart
• If these conditions aren’t met, RNA Polymerase can’t bind to the DNA and no transcription occurs.
![Page 14: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/14.jpg)
Elongation
• How the RNA strand is built• RNA Polymerase matches the
appropriate (complementary) nucleotides to the DNA template strand– Template strand = the actual
strand RNA Polymerase uses to build RNA
– Coding (Nontemplate) strand = not used for building RNA, but has the same sequence as the RNA.
![Page 15: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/15.jpg)
Building the RNA• The RNA Polymer grows in a 5’-3’ direction
• RNA Polymerase only adds new nucleotides on to the 3’ end.
• Considering this, in what direction must the template strand of DNA be running?
– 3’-5’ (since it is building its complement)P
OPP
PPP
OPP
P
OPP
P
O
5’
3’
5’
3’
5’
3’
5’
3’
![Page 16: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/16.jpg)
Question …
• In terms of the sequence, how will the RNA differ from the sequence of the coding strand in the DNA?– T’s are replaced with U’s
![Page 17: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/17.jpg)
Termination • How transcription of RNA ends• RNA Polymerase recognizes a
termination signal on the DNA template– Usually a long string of A’s or a
series of A’s and T’s
• RNA Polymerase falls off the DNA template
• Stability of mRNA is minutes hours (depends on type of cell and RNA)
![Page 18: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/18.jpg)
Question…
• How do the specific chemical properties of the termination sequence cause termination to occur?– There are only 2 hydrogen bonds between A
and T/U– With a string of A’s and U’s, there are much
fewer bonds to hold the DNA template and RNA together they separate transcription ends
![Page 19: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/19.jpg)
TranslationTranslation
• Using the mRNA code to create the appropriate protein.
• Occurs in the cytoplasm/on the rough ER
• Sequence of 3 nucleotides codes for a particular amino acid = codon
• 64 different codons
![Page 20: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/20.jpg)
Question…
• Why can’t 1 or 2 nucleotides code for an amino acid?– Not enough combinations to code for all 20
amino acids– With 1 nucleotide only 4 possibilities (A, C,
G, U)– With 2 nucleotides only 4 x 4 = 16
possibilities (AA, AU, AC, AG, CC, …)
![Page 21: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/21.jpg)
The codon table
![Page 22: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/22.jpg)
tRNA
• tRNA brings the correct amino acid to match with the mRNA codon
• Each tRNA holds a specific amino acid and has a particular anticodon.
• Aminoacyl tRNA synthetases are enzymes that attach the correct amino acids to the tRNA
Amino acid attached
here
![Page 23: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/23.jpg)
Question…
• For the anticodon shown in the diagram, what would the complementary codon on the mRNA be?– 5’ UUC 3’
• Which amino acid is attached to this tRNA?– Phe
![Page 24: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/24.jpg)
Ribosomes
• Made up of 2 subunits• Composed of rRNA and protein• Not specific to any particular
protein– can be used to translate any RNA into protein
• Workbench for translation – holds mRNAs and tRNAs in the correct positions to assemble protein.
![Page 25: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/25.jpg)
Ribosomes
• 3 sites on the ribosome– A site = where tRNA
first binds to mRNA – P site = where the amino
acid is added on to the polypeptide chain
– E site = exit site
![Page 26: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/26.jpg)
Translation
• Begins with the Start codon = AUG– Codes for methionine (Met)– Not the same thing as +1
![Page 27: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/27.jpg)
Translation
• Ribosome moves along mRNA in a 5’->3’ direction, catalyzing the translation of the mRNA into protein – breaks bond between
tRNA and amino acid – creates a new peptide
bond to link it to polypeptide chain
![Page 28: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/28.jpg)
Question…
• How does the mRNA know if it is correctly matched to the tRNA?– Hydrogen bonding between the bases is correct
![Page 29: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/29.jpg)
Stopping Translation
• Ribosome is released when a stop codon is reached– UAA, UAG, UGA = stop codons (don’t code for any
tRNA anticodons)– A release factor binds to the mRNA instead– Ribosome breaks apart, mRNA and protein are
released
![Page 30: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/30.jpg)
Summary of Protein Synthesis
• In Eukaryotes
• How is it different in prokaryotes?
![Page 31: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/31.jpg)
Why is this important?
1. Changes in the DNA sequence will lead to changes in the transcribed _________.
2. This results in a different codon which may code for a different ______________.
3. A different ___________ means a different R group.4. A different R group may have different chemical
properties.5. These different chemical properties may lead to a
different protein ____________.6. A different protein structure may affect its _________!7. See how this is all starting to connect! Exciting!!!
![Page 32: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/32.jpg)
Why is this important?
1. Changes in the DNA sequence will lead to changes in the transcribed RNA.
2. This results in a different codon which may code for a different amino acid.
3. A different amino acid means a different R group.4. A different R group may have different chemical properties.5. These different chemical properties may lead to a different
protein structure.6. A different protein structure may affect its function!
7. See how this is all starting to connect! Exciting!!!
![Page 33: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/33.jpg)
microRNAs and RNAi
• Small, single stranded RNA molecules (miRNAs and siRNAs)– microRNA = miRNA– Small interfering RNA = siRNA
• Bind to complementary sequences in mRNA molecules
• Can control the expression of (translation of) specific RNA molecules
![Page 34: Protein Synthesis Transcription and Translation AP Biology Unit 2](https://reader035.vdocuments.us/reader035/viewer/2022070408/56649e4f5503460f94b46233/html5/thumbnails/34.jpg)
Question…
• How will microRNAs disrupt translation?– Block translation by creating a physical road block– RNA-RNA binding also marks the mRNA for
degradation
• Called RNAi = RNA interference