1. Structure of DNA DNA is made up of a long chain of nucleotides
Each nucleotide has three parts
A phosphate group
A deoxyribose sugar
A nitrogen-containing base

2. Structure of DNA
The nitrogen containing bases are the only difference in the four nucleotides

3. Structure of DNA
DNA is a double helix, in which two strands are wound around each other
Discovered by Watson and Crick
Nucleotides always pair in the same way
Base-pairing rules
A pairs with T
C pairs with G

4. Structure of DNA The backbone is connected by covalent bonds
The bases are connected by hydrogen bonds

5. DNA Replication Replication- copies the genetic information
A single strand of DNA serves as a template for a new strand
The rules of base pairing direct replication
When is DNA replicated during cell cycle?
Each body cell gets a complete set of identical DNA

6. DNA Replication How does replication work?
Proteins carry out the process of replication
DNA serves only as a template
Enzymes and other proteins do the actual work of replication
Enzymes unzip the double helix
Free-floating nucleotides form hydrogen bonds with the template strand

7. DNA Replication How does replication happen?
DNA polymerase enzymes bond the nucleotides together to form the double helix
Polymerase enzymes form covalent bonds between nucleotides in the new strand

8. DNA Replication
Two new molecules of DNA are formed, each with an original strand and a newly formed strand
Replication is fast and accurate
DNA polymerase can find and correct errors

9. Transcription
Transcription- converts a gene into a single-stranded RNA molecule
RNA carries DNA’s instructions
Central Dogma- information flows in one direction from DNA to RNA to proteins
Replication
Transcription
Translation
RNA is a link between DNA and proteins

10. Transcription How does DNA differ from RNA?
RNA has ribose sugar instead of deoxyribose
RNA has uracil instead of thymine
RNA is single stranded instead of double stranded

11. Transcription Transcription copies DNA to make a strand of RNA
Makes three types of RNA
Messenger RNA (mRNA) carries the message that will be translated to form a protein
Ribosomal RNA (rRNA) forms part of ribosomes where proteins are made
Transfer RNA (tRNA) brings amino acid from the cytoplasm to a ribosome

12. Transcription How does transcription happen?
RNA polymerase binds to DNA and separates the DNA strands
RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA
How does RNA polymerase know where to start and stop making a RNA copy of DNA?
Start and stop signals- specific base sequences

13. Transcription

14. Translation Amino acids are coded by mRNA base sequences
Translation converts mRNA messages into polypeptides or proteins
Codon- sequence of three nucleotides that codes for an amino acid

15. Genetic code- language of mRNA instructions, matches each codon to its amino acid or function
Start codon= AUG
Stop codon= UGA, UAA, UAG
Translation

16. Translation Translation- production of proteins
Ribosome
What happens during translation?
Messenger RNA is transcribed in the nucleus, and released into cytoplasm
Translation begins at AUG (start codon), as each codon of the mRNA moves through the ribosome, amino acid is brought into ribosome by tRNA, amino acid is transferred to growing polypeptide chain
tRNA has 3 unpaired bases (anticodon)- complimentary to one mRNA codon
Polypeptides join assembly line, continues until one of the three stop codons is reached
Protein synthesis

17. Translation