TRANSCRIPTION/TRANSLATIONProtein Synthesis

RNARIBONUCLEIC ACID

SINGLE STRANDED

RESPONSIBLE FOR BRINGING THE GENETIC INFO. FROM THE NUCLEUS TO THE CYTOSOL!

RNA NUCLEOTIDE

Phosphate group

Sugar molecule (ribose)

Nitrogenous basesAdenine – URACILCytosine - guanine

RNA

*

3 KINDS OF RNA mRNA – (messenger) brings info from DNA in

nucleus to cytosol in eukaryotic cells (uncoiled)

tRNA –(transfer) brings amino acids to mRNA for translation (hairpin shape)

rRNA –(ribosomal) most abundant, rRNA makes up the ribosomes where proteins are made (globular)

TRANSCRIPTION!!DNA RNA

1. INITIATION PHASE- RNA polymerase-initiates

transcription by binding to region on DNA called

PROMOTER (beginning of the gene)

only ONE of the DNA chains will be used for transcription

it’s called the TEMPLATE (promoter dictates which of the

two strands will be used)

2. ELONGATION PHASE- RNA POLYMERASE

attached to first DNA nucleotide of template chain –

then begins adding complementary RNA nucleotides-

Read in a 3’ to 5’ direction

CONT. TRANSCRIPTION

3. TERMINATION PHASE- transcription continues until RNA polymerase reaches a TERMINATION SIGNAL on the DNA- STOP CODON

4. RNA polymerase releases both the DNA mol. And newly formed RNA mol.

TRANSCRIPTION

RNA REPLICATIONS

PROKARYOTESTranscription and translation occur in the SAME place!

NO NUCLEUS!

EUKARYOTES 1. Before RNA leaves the nucleus: 5’ G (guanine) cap is attached 3’ polyA (adenine) tail is attached “many”

2. These protect the RNA from attach by cellular enzymes and help ribosomes to recognize the mRNA cap & tail are NOT translated

CONT. EUKARYOTES 3. INTRONS (non coding sequence) are

removed

4. EXONS (part of gene that are expressed) are joined to produce a mRNA molecule with a continuous coding sequence.

NOW RNA CAN LEAVE THE NUCLEUS!

PROTEIN SYNTHESIS

PROTEINS CARRY OUT THE GENETIC INSTRUCTIONS ENCODED IN AN ORGANISM’S DNA!!!!

TRANSLATIONTHE PROCESS OF ASSEMBLING FROM INFO. ENCODED IN A MRNA!

1. mRNA leaves nucleus 2. mRNA migrates to ribosome in cytosol for

protein synthesis 3.amino acids floating in cytosol are transported

to ribosomes by tRNA mole 4. peptide bonds join the amino acids to make

polypeptide chain

VOCABULARY!

1. GENETIC CODE: correlation between a nucleotide sequence and an amino acid sequence

2. CODON: 3 mRNA nucleotides, codes for a specific amino acid (64)

3. START CODON (AUG) & a.a. methionine

4. STOP CODON (UAA, UAG, UGA) 5. ANTICODON – 3 tRNA nucleotides

carrying a specific amino acid!

20 DIFFERENT KINDS OF AMINO ACIDS

….. But only 4 different kinds of nitrogen bases

INITIATION CODON MARKS THE START OF AN MRNA MESSAGE

3 PHASES:

1. INITIATION2. ELONGATION3. TERMINATION

RIBOSOMEFACTORY FOR POLYPEPTIDES Two subunits:

Large subunit (top) Small subunit (bottom)

P SITE – HOLDS TRNA CARRYING GROWING POLYPEPTIDEA SITE – HOLDS TRNA CARRYING THE NEXT AMINO ACID TO BE ADDED

Forms a peptide bond

PROTEIN SYNTHESIS

*

PROTEIN SYNTHESIS

!

THE SUMMARY!- CENTRAL DOGMA