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

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

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

4. DNA structure nucleotide Condensation polymerisation of the
deoxyribose nucleotides

5. 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

6. 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)

7. 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

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

9. Transcription

10. 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

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

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

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

14. Translation A polypeptide chain forms
Eventually a stop codon is reached

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

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

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