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RNA & PROTEIN SYNTHESIS. SC STANDARD B-4 STUDENTS WILL DEMONSTRATE AN UNDERSTANDING OF THE MOLECULAR BASIS OF HEREDITY. Topic: Protein Synthesis. EQ : HOW WOULD YOU COMPARE TRANSCRIPTION &TRANSLATION? Notebook: page 98. GENES:. - PowerPoint PPT Presentation
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SC STANDARD B-4STUDENTS WILL DEMONSTRATE AN
UNDERSTANDING OF THE MOLECULAR BASIS OF HEREDITY
RNA & PROTEIN SYNTHESIS
EQ: HOW WOULD YOU COMPARE TRANSCRIPTION &TRANSLATION?
Notebook: page 98
Topic: Protein Synthesis
GENES:are coded DNA
instructions that control the production of proteins within a cell.
RNA (Ribonucleic Acid)single stranded
nucleic acid5-carbon sugar is
ribosePhosphate group 1 of 4 nitrogenous
bases:1. adenine 2.
guanine3. cytosine 4.
uracil
Types of RNA1. Messenger RNA (mRNA)carries copies of
instructions for assembling proteins from the gene (in nucleus) ribosomes (in cytoplasm or RER)
mRNAsingle strand of
nucleotidesread in groups of 3
called codonslook at the 2 codons
on this slide: What sequence of nucleotides on DNA did this segment of mRNA come from?
Ribosomal RNA : rRNAwith proteins
make up ribosomes
ribosomes made of 2 subunits: 30S and 50S
Transfer RNA: tRNAtransfers each of the amino acids to the ribosome as is specified by the code in mRNA
one end has the anticodon
other end the a.a.
anticodon: group of 3 bases that are complimentary to the codon on mRNA
TRANSCRIPTIONINVOLVES TRANSCRIBING (copying) THE CODE IN DNA MAKING mRNA
INVOLVES TRANSLATING the CODE into AMINO ACIDS POLYPEPTIDE CHAINS PROTEINS
mRNA, tRNA, rRNA
PROTEIN SYNTHESISTRANSLATION
TRANSCRIPTIONmRNA molecules are made by copying part of a nucleotide sequence of DNA into a complimentary (C’) sequence in mRNA
Steps:1. RNA Polymerase opens DNA
2.RNA Polymerase uses 1 of the DNA strands as templateuses C’ base pair
rules
RNA Polymerase binds to DNA at certain points called “promoters”
Transcription
after unwinding a short portion of the double helix, RNA Polymerase moves along 1 of the DNA strands making a strand of RNA using base-pair rules except there is no T in RNA: A is paired with U (Uracil)
Transcription
Transcription
RNA Polymerase moves along the DNA until it hits a signal to stop.
this strand of RNA is called pre-mRNA
Transcription
portions of DNA called introns do not code for proteins
DNA portions that code for proteins called exons.
introns get cut out of pre-mRNA and the exons get spliced together
http://www.dnalc.org/view/16938-3D-Animation-of-RNA-Splicing.html
RNA Editing
http://www.johnkyrk.com/DNAtranscription.html
Transcription Animations
The Genetic Codeis the “language”
of the mRNA instructions
written in a language that only has 4 “letters”:G, C, A, & Umust code for 20 amino acids
is read 3 letters at a time
every 3 consecutive letters codes for 1 of the 20 a.a., a start signal, or a stop
The Genetic Code
The Genetic Codecodon: is a “word” in the code
consists of 3 consecutive nucleotides that specify an a.a., a stop, or a start
The Genetic CodePage of Notebook: “Crack the Code”Quick Lab from
page 303 of textbook
TRANSLATIONcell uses information from mRNA to produce proteins
Step 1mRNA attaches to ribosome
1st codon codes for methionine
tRNA with anticodon complimentary to codon in mRNA attaches to ribosome, delivering correct a.a.
TranslationStep 2
Step 3peptide bond forms between a.a brought to ribosome by 1st & 2nd tRNA
ribosome only holds 2 tRNA so 1st one leaves ribosome as 3rd one “docks”
Process repeated until “stop” codon
TranslationStep 4
Step 5polypeptide chain falls off ribosome
Ribosome free to start another peptide chain
http://www.wisc-online.com/Objects/ViewObject.aspx?ID=AP1302
TranslationAnimation
TRANSCRIPTIONDNA mRNAnucleus
mRNA cytoplasm or RER
mRNA + ribosome + tRNA protein
PROTEIN SYNTHESISTRANSLATION
Handout: Genetic Code for KeratinPage of NotebookAnswer questions 1-4
Quick Lab