rna structureandfunction transcription translation
TRANSCRIPT
RNAStructure
and Function
Transcription Translation
RNA versus DNA
The Sugar
OHO
OH
OHOH
Ribose
Four RNA Bases
N
N
NH
N
NH2
N
NH
NH
N
NH2
O
N
NH
NH2
O
Adenine Uracil
Guanine Cytosine
NH
NH
O
O
Types of RNA
mRNA
mRNA = messenger RNA• Represents the sequence of codons (mRNA language) from the DNA strand.
• Brings the sequence to the
ribosomes (site of protein synthesis) in the cytoplasm.
• Provides the sequence for the synthesis of specific protein from the amino acids (found in cytoplasm).
rRNArRNA = ribosomal RNAFunction:
forms a complex with various proteins and make a structure called ribosome, and this complex reads the coded sequence in mRNA to link amino acids together into particular proteins.
Transfer RNA
• tRNA brings the amino acids to the ribosomes
The Central Dogma of Life.
replication
Transcription
Transcription is the process by which RNA is built from a template of DNA
Transcription
Transcription
The mRNA sequence leaves the nucleus and enters the cytoplasm to be “read”.
Translation
Translation
Translation is the process by which protein is made from an mRNA template
Codons• 4 different bases make up
RNA
• RNA is read in groups of three called a triplet
• One triplet is called a CODON
• Each CODON represents a specific amino acids
• Amino acids build proteins
Codons
Why Three Bases per Codon?
A one base code: 41 = 4 combinations
A two base code: 42 = 16 combinations
A three base code: 43 = 64 combinations
There are twenty amino acids, so a three-base code is the minimum required.
Making a protein
• mRNA from nucleus travels through the cytoplasm to the ribosome
• On the mRNA, a start codon: AUG signals the beginning of a protein
• tRNA delivers specific amino acids and creates a polypeptide chain
• A release factor ends the process
