rna structureandfunction transcription translation

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

Protein Synthesis