PSYD33H3 Lecture Notes - Lecture 3: Chain Termination, Prokaryote, Ribosomal Rna

19 views5 pages
29 Apr 2012
School
Department
Course
PSYD33 Lecture 3: January 25, 2012
Film
Adaptor molecule
tRNA
basis for DNA: atcg
Acridines
Deleting or adding one base pair for viral DNA,
o Induce 1 mutation in gene or virus, all amino acid will get changed; get shifted
o If eliminated 2 base pairs, same result
o But if eliminate/ add 3 base pairs, remaining portion of that gene will make sense (amino
acid sequence will all be in register)
o E.x. “old men are fun”
Genetic code made of 3 bases each
Codons: each codon representing a unique protein/ amino acid
Each codon codes for 3 base pairings in DNA
Protein = strings of amino acid
20 essential amino acids in mammals, humans
Genetic code: sequence of DNA with 3 base pairings; that through RNA specific for an amino
acid
Phenylalanine
Codon UUU = phenylalanine
Codon AAA = lysine
Codon CCC = proline
Codon GGG = glycine
Specific nucleotides pairings; when 3 together (genetic word/ codon) attracts particular amino
acid in protein chain
Early days, figured out genetic code by first using same word consisting of same base pairings
and see which amino acid was produced by it
Strings of protein consisting of same amino acid = UUU
Then putting in different letters in different codons in different proportions and seeing what it
looked like
Found, by experimental error getting same portion of amino acid in protein chain in portion of
the codons that went into mixture
Showed process of how DNA ultimate protein sequence was discovered
Relationship btw nucleotides and amino acids
64 possible combinations = codons and 20 amino acids
Some amino acids coded for by more than one codon redundancy
i.e. UCU, UCC, UCA, UCG = all code for serine
with 3 positions for letters in word (UCGA) = 64 possibilities; each codes for a particular amino
acid
particular codon codes for particular amino acid in eventual protein produced by that gene
each codon, each sequence of 3 basis; only codes for 1 amino acid
lack of ambiguity but redundancy
only differs by last position; same first 2 positions
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 5 pages and 3 million more documents.

Already have an account? Log in
3 stop codon: don’t code for a particular amino acid serve as punctuation that message ends
here
Signaling that protein is complete
1 codon = AUG codes for methionine + and also functions as start codon (start signal)
All mRNA begins with AUG
Serves as unambiguous marker for starting where start beginning of set of 3 elements
interpereted as codon
Know where to start defining the triplets; where to read the genetic code
Beginning of reading frame
mRNA starts with AUG that’s the first triplet and anything after that in triplets is the genetic
code
start and stop codons where new protein is to start and stop
RNA produced attracted to amino acids btw start and stop codons
All polypeptides start with methionine
Universal; every genetic system using same triplet code
Same codon assigned to same amino acid; same start and stop codons
Genetic engineering take gene in one organism and function in another organism
Replication, transcription and translation differs little btw organism
Machinery recognizes same code read same sequence
Ex. Take gene produces human insulin into e.Coli bacteria produce human insulin quickly
which we can then use
Modify organisms by inserting DNA- plants less susceptible to insects, anti- freezing more
resistant = genetically modified organisms (GMA)
Gene therapy = modifying ourselves
Take functional version of that gene into cells of individual; another source of producing gene
product to substitute for diseased gene
Genetic code = universal code
Shared vocabulary of genetic code suggests all life arose from single organism long time ago
Sequence of amino acid and nucleotides arose early in origin of life
From DNA to RNA = TRANSCRIPTION (copy)
(Replication) DNA (transcription) RNA (translation) Protein synthesis
Transcription: DNA directed RNA synthesis (DNA RNA)
RNA as nucleic acid sequence of nucleotides
DNA rasncribed into RNA form
Function of RNA = act as intermediate/ messenger from DNA onto proteins through translation
DNA + RNA as nucleic acids
Key enzyme = RNA polymerase (make more RNA) depends on complimentary base pairings
of nucleotides (AUGC = A+U; C+G)
Transcription requires DNA to unwind from double helix structure by RNA polymerase
RNA polymerase adds complimentary bases
Transcription vs. Replication
Helicase to unwind double helix
RNA polymerase can open up helix itself
Only one of DNA strand is transcribed by RNA polymerase
o Only need one side transcribed because other side would be same information
(complimentary info)
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 5 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Deleting or adding one base pair for viral dna, Induce 1 mutation in gene or virus, all amino acid will get changed; get shifted. If eliminated 2 base pairs, same result: but if eliminate/ add 3 base pairs, remaining portion of that gene will make sense (amino acid sequence will all be in register, e. x. Genetic code made of 3 bases each. Codons: each codon representing a unique protein/ amino acid. Each codon codes for 3 base pairings in dna. 20 essential amino acids in mammals, humans. Genetic code: sequence of dna with 3 base pairings; that through rna specific for an amino acid. Specific nucleotides pairings; when 3 together (genetic word/ codon) attracts particular amino acid in protein chain. Early days, figured out genetic code by first using same word consisting of same base pairings and see which amino acid was produced by it. Strings of protein consisting of same amino acid = uuu.

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
Booster Classes
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
Booster Classes