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33 Cards in this Set
- Front
- Back
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mRNA
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messenger RNA
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Translation
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to make protein from RNA, you must break the code
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Minimum number to make twenty words (of amino acid possibilities)
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4^3 = 64
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How does the code work?
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1. code words are 3 nucleotides long
2. 64 codons, or code words 3. codes occur in series, keeping it ordered 4. codons are non overlapping READ THE RNA 5' TO 3' |
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The genetic code
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is redundant, several codons can specify the same amino acid
Uracil - RNA Thymine - DNA the code shows RNA because it's decoded by a ribosome |
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How many codons make an amino acid?
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61
3 do not because 2 are stop codes and 1 is a start |
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Start codon
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AUG
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Stop codon
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UAA, UAG, UGA
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How is an RNA copy made?
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strand are separated, one strand is used as a template to build RNA, and uses complementary base pairing
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What is needed to make RNA?
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a gene to serve as a template, ribonucleotides, and several enzymes and proteins
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What is transcription catalyzed by?
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RNA polymerase builds the RNA, it can initiate polynulceotide synthesis and no primer is needed
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Where does transcription begin?
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starts on the promoter
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How many templates in transcription?
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One, the promoter decides which one is the template strand
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What direction does it go?
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cannot add to the 5' end, so it builds 5' to 3', adding to the 3'
READ 3' TO 5' to determine each template strand |
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RNA Promoter
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Contains the start site, where RNA polymerase does its thing
transcription ends at the terminator |
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Non template strand
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the strand that isn't being transcribed the promoter DNA polymerase will run along the template strand
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Where will mRNA go after transcription?
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to the cytosol
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Three Steps to RNA Transcription
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1. Initiation
2. Elongation 3. Termination |
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Initiation
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the RNA polymerase attaches to the start site
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Elongation
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the RNA polymerase begins unwinding the template strand that it read 3' to 5', detaching it
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Termination
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the completed RNA transcript is off the DNA strands and the RNA polymerase come off the strands
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How to count polypeptide chain in mRNA
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find the first start codon (AUG), and then the last stop codon (UAA,UAG,UGA)
count in threes until you reach the stop. that's how many there will be |
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Coding region
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region between stop and start codons
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How is RNA translated?
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1. codons are decoded by ribosomes
2. requires transfer RNAs 3. tRNAs recognizes codons through complementary base pairing |
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How does a ribosome decode?
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requires tRNAs
and then they recognize the codons by complementary base pairing |
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What are tRNAs?
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80 nucleotides long RNAs forming a 3-D L shape
they are held together through hydrogen bonds |
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Ends of the tRNAs
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one end has a 3 nucleotide sequence called an anticodon which is complementary base paired to another codon
the other end carry the amino acid encoded by the codon they recognize to the ribosome |
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How is the correct amino acid joined to each RNA?
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by tRNAs syntheses (they're enzymes)
there's 20, one for each amino acid |
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What's a ribosome and what does it do?
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a large complex of polypeptides, with rRNA inside
has 2 subunits and a passage for the mRNA to go through contains 3 binding site: A, P, E |
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The Ribosome Does 3 Things
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1. facilitates base pairing: b/w a codon in mRNA and a tRNAs anti codon
2. catalyzes: the dehydration reaction that joins amino acids covalently, making peptide bonds 3. maintains the 'frame': of reading the polypeptide chain, from the start codon location |
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What's needed to make a protein?
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mRNA
a set of amino acyl tRNAs to complement all of the codons a ribosome |
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Where do tRNAs and rRNAs come from?
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there must be genes encode for them, encoded by the genome and made by the transcription?
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What is a gene?
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a region of DNA encoding either a polypeptide or RNA
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