WHAT DO YOU THINK?

WHAT DO YOU THINK?

STRANGE HUH?

TRANSCRIPTION & TRANSLATION

OVERVIEW

Transcription TranslationDNA RNA

Protein

Characteristics

Make Short Notes

TRANSCRIPTION & TRANSLATION

TRANSCRIPTION

DNA never leaves the nucleus

Proteins are synthesized in the cytoplasm

Therefore a copy of the each gene is made using messenger RNA to carry the message from Nucleus to the Cytoplasm

Transcription Is the synthesis of an RNA molecule with a base pair complementary to a section of DNA

TRANSCRIPTION

Usually only a small part of the DNA molecule is transcribed at one time – a section that codes for making one polypeptide is called a GENE

The process starts by the unzipping of the DNA Helix by the enzyme DNA Helicase which break the H+ bonds

Free RNA nucleotides slot into place against the DNA strand i.e. A-U, G-C

Temporary H+ bonds results to hold the RNA in place and Phosphodiester bonds are created between the RNA nucleotides

TRANSCRIPTION

This process is catalyzed by the enzyme RNA polymerase this also ensures that the sequence of amino acids is correct

This elongation of the mRNA continues until the end of the gene or until a STOP codon (ATT, ATC, ACT) is reached

The DNA may zip back up and the mRNA strand exits the nucleus via the nuclear pore into the cytoplasm

TRANSLATION

Translation is the process by which the code for making proteins (carried by the mRNA) is used to sequence a polypeptide chain

The sequence of codons is carried on the mRNA

The AUG (Methionine ) codon indicates the start of an amino acid sequence

The mRNA is held in a cleft in the ribosome in the cytoplasm

TRANSLATION

A tRNA complementary to the 1st start codon binds to the mRNA (INITIATION)

Each tRNA carries with it a corresponding amino acid

As the triple codons are read, complementary tRNA molcecules with their amino acids bind to the mRNA

Upon completion , each tRNA molecule breaks free leaving behind its corresponding amino acid

TRANSLATION

Peptide bonds form between the amino acids resulting in elongation of the polypeptide

The released tRNA is now available to be reloaded with its complementary amino acid

The polypeptide build up until a STOP codon is reached on the mRNA (TERMINATION)

ANSWERS

ACTIVITY 1

TACCGGGTGTACGGGGTG DNA Coding Strand

AUGGCCCACAUGCCCCAC mRNA Strand

met ala hist met pro hist Polypeptide Sequence

N.B. The anticodons on the tRNA are complementary to the codons on the mRNA

ANSWERS

Assessment

Stage A: Transcription

Stage B: Translation

Outline the Process occurring at Stage A:

It Is the synthesis of an mRNA molecule with a base pair complementary to a section of DNA. Usually only a small part of the DNA molecule is transcribed at one time . The process starts by the unzipping of the DNA Helix by the enzyme DNA Helicase which break the H+ bonds. Free

RNA nucleotides slot into place against the DNA strand.

ANSWERS

Assessment cont’d

Temporary H+ bonds results to hold the RNA in place and Phosphodiester bonds are created between the RNA nucleotides. This process is catalyzed by the enzyme RNA polymerase this also ensures that the sequence of amino acids is correct. This elongation of the mRNA continues until the end of the gene or until a STOP codon (ATT, ATC, ACT) is reached. The DNA may zip back up and the mRNA strand exits the nucleus via the nuclear pore into the cytoplasm

THE END

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