rna

RNA

• Three types of RNA:1. Messenger RNA (mRNA)

2. Ribosomal RNA (rRNA)

3. Transfer RNA (tRNA)

• Three types of RNA:1. Messenger RNA (mRNA)

An RNA molecule that carries copies instructions for the assembly of amino acids into proteins from DNA to the rest of the cell.

• Codons– three-nucleotide sequence on messenger RNA

(mRNA) that codes for a single amino acid.

• Three types of RNA:2. Ribosomal RNA (rRNA)

An RNA molecule that makes up part of the ribosome. It is a key player in the translation process.

Ribosomal RNA

Proteins

Ribosome

• Three types of RNA:3. Transfer RNA (tRNA)

Brings an anticodon, which is complementary to a codon on the mRNA strand.

Anticodon

Amino Acid

PROTEIN SYNTHESIS

Protein Synthesis

• Cellular process in which proteins are made

• Two steps– Transcription (in the nucleus)

• (DNA to mRNA)– Translation (in the cytoplasm)

• (mRNA to proteins)

• Transcription– Process in which part of the nucleotide

sequence of DNA is copied into a complementary sequence in RNA

1. RNA polymerase binds to DNA in nucleus and separates the strands

2. RNA polymerase then reads the DNA template and assembles an RNA strand

3. DNA zips back up, mRNA formed.

Transcription (In Nucleus)

Transcription

RNADNA

RNApolymerase

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

Nuclear Envelope

Decoding of a mRNA message into a polypeptide chain (of amino acids)

1. mRNA leaves Nucleus and enter cytoplasm

2. mRNA attaches to rRNA3. rRNA decodes the codons by

matching it to the anticodon on the tRNA

4. The amino acids on the tRNA are bonded together and released

5. A protein is formed

Translation (in Cytoplasm)

Translation (in cytoplasm)

Overview

Overview

Decoding into Amino Acids• Based on the mRNA codons

Special Codons• Start Codon (1) Methionine AUG

• Stop Codons (3) UCG UAG UGA

The Genetic CodeIf we had this mRNA sequence:

UCGCACGGUThe sequence would be read three bases at a time as:

UCG – CAC – GGUThe codons represent the different amino acids:

Serine-Histidine-Glycine

The Codon Wheel

The Codon Chart