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