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
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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
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PROTEIN SYNTHESIS
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THE SUMMARY!- CENTRAL DOGMA