from gene to protein. dna:nucleotides are the monomers proteins: amino acids are the monomers dna:in...
TRANSCRIPT
PROTEIN SYNTHESISFrom gene to protein
How does information get from DNA to proteins?
DNA:nucleotides are the monomersProteins: amino acids are the monomersDNA:in the nucleusProteins:synthesized in cytoplasm
Overview
DNA -mRNA-Protein = gene expression-central dogma of biology-a section of DNA's code (a gene) is copied
(transcribed) onto mRNA.-mRNA carries the code to the ribosome
where the code is translated, with the help of tRNA, into a sequence of amino acids (polypeptide)
The genetic code
-three bases on DNA = triplet-code for three bases on mRNA = codon-codes for one amino acid
Transcription details
- occurs in nucleus- purposes is to produce a copy of DNA
called messenger RNA which carries genetic information to the cytoplasm.
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Transcription: initiation
-One strand of DNA acts as template- RNA polymerase binds to promoter region
which includes the initiation site on a section of DNA (gene)
Elongation
- RNA polymerase moves along the DNA strand unwinding and unzipping, separating the strands by breaking the hydrogen bonds.
- the mRNA strand grows. It is complementary to the DNA template
Termination
- transcription continues until a termination site is reached
-mRNA strand is released
TranscriptionWatch video clip:
http://youtu.be/WsofH466lqk
Complete questions in notes and go over
Triplet codon system
- triplet = 3 bases on DNA- codon= 3 bases on mRNA- codes for a specific amino acid. One of
twenty possible amino acids. Redundancy built into system. 64 possible codons
- universal code since it used by all organisms
-stop and complete questions/ go over
Translation
- purpose is to translate info on mRNA into a chain of amino acids that fold into a functional protein.
- one gene codes for one protein
Ribosomes structure & function
- ribosomes have two subunits made up of protein and RNA
- site of attachment of mRNA and tRNA -site of protein synthesis
Transfer RNA
- a folded strand of RNA with a site for amino acid to attach at one end.
- the other end has three bases exposed which complement with an mRNA codon
- called an anticodon
Transfer RNA and ribosomes
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Translation details
- initiation- elongation- termination
Initiation
- mRNA attaches to small ribosomal subunit- start codon AUG- tRNA carrying amino acid methionine pairs
with codon AUG (anticodon UAC on tRNA)- large ribosomal subunit sandwiches mRNA-2 codon sites on ribosome "P" & "A"- "P" site occupied, "A" site empty
initiation
Elongation
- a second tRNA with an anticodon moves into the "P" site
- covalent peptide bond forms between a.a of "A" site and a.a of "P" site.
-"P" site tRNA breaks away to get another a.a
- ribosomal complex shifts along mRNA to next codon. Process continues, polypeptide grows
Elongation
Termination
- elongation continues until a "stop" codon is reached
- UAA, UAG, UGA- release factor ( a special protein) binds to
the A site.- the polypeptide is released and the
ribosome separates into the large and small subunits
Termination
Protein synthesis Video
http://youtu.be/5bLEDd-PSTQComplete questions 1-3