Nucleic acids DNA & RNA Made up of nucleotides: phosphate base pentose sugar

Nucleotides 2 types of base: Pyrimidines - Purines Cytosine C Thymine T Purines Adenine A Guanine G

Complimentary base pairing Adenine will only bind with Thymine Cytosine will only bind with Guanine T A C G

DNA structure nucleotide Condensation polymerisation of the deoxyribose nucleotides

Replication—worksheet hw During cell division the DNA must replicate The enzyme helicase unwinds the DNA double helix The exposed bases bind to free floating nucleotides in the nucleoplasm DNA polymerase binds the complimentary nucleotides Replication is semiconservative

The genetic code The sequence of nucleotide bases forms a code Each ‘code word’ has three letters– a triplet code Each codon codes for a specific amino acid e.g: GGG = proline CGG = glycine ATG = tyrosine ACT = stop (no amino acid)

Protein synthesis The DNA codes for proteins A copy of DNA (mRNA) is made in the nucleus (transcription) The mRNA is used to make a protein (translation) in the cytoplasm

Transcription Helicase unwinds the DNA Free nucleotides join onto complimentary bases RNA polymerase links adjacent nucleotides The completed mRNA moves out of the nucleus

Transcription

Three types of RNA Messenger RNA- made in the nucleus but sent to the ribosome mRNA Ribosomal RNA- makes up the ribosome (site of protein synthesis) with protein rRNA Transfer RNA-brings the appropriate amino acid to the ribosome for protein synthesis tRNA

Translation mRNA binds to a ribosome tRNA carries an amino acid to the ribosome

Amino acid activation transferRNA: tRNA binds onto a specific amino acid

Translation A second tRNA brings another aa The two amino acids bind The process repeats

Translation A polypeptide chain forms Eventually a stop codon is reached

Acknowledgements Animated cell models used by kind permission of The Virtual Cell website: .

Quiz 1. Which process involves tRNA: transciption translation DNA replication gene mutation

Quiz 2. The formation of RNA does not involve: ribose sugar thymine removal of water phosphate