1. Replication and Transcription
DNA
Replication and Transcription

2. DNA Structure: the backbones:
-Consist of two five carbon sugar/phosphate backbones that are covalently bonded to create the rungs of the twisted ladder
-Each of the backbones is antiparallel (they run in opposite ways).
-One strand is the 3’ (the phosphate bonds on the third carbon), the other is the 5’ (the phosphate bonds to the fifth carbon). The sugars are oriented in opposite directions.

3. DNA Structure: the rungs
Each deoxyribose sugar is covalently bonded to a nitrogen base
The bases in between the sugars are bonded through a hydrogen bond
-Adenine bonds to Thymine
-Cytosine bonds to Guanine

4. DNA REPLICATION
The copying of 1 DNA double helix to create 2 identical double helixes.

5. Steps of DNA REPLICATION
Helicase (enzyme) separates the double helix by breaking the hydrogen bonds between the bases. 5’ 3’ 5’ 3’ ↑
Enzyme cuts here

6. Steps of DNA REPLICATIONG A G T C
Spare nucleotides pair up with bases in the original chain.

7. Steps of DNA REPLICATIONG A G T C
DNA Polymerase binds new nucleotides to the 3’ end of the new chain.

8. -DNA polymerase can ONLY add nucleotides in the 5’ direction, so it must start from the 3’ end of the parent chain.
The leading strand is the orginal strand that has the 3’ end and adds nucleotides continuously
The lagging strand is the original strand that has the 5’ end, therefore DNA polymerase starts in the middle of the strand and creates fragments as it moves.
These Ozaki Fragments are later put together by the enzyme DNA ligase.

9. Overview of Replication

10. END RESULT
The new strands of DNA combine with histones (proteins) to form nucleosomes that condense to form chromatin, that form chromosomes.

11. Transcription DNA chains are separated just enough to copy 1 gene
RNA nucleotides H bond to exposed DNA bases
RNA nucleotide includes the sugar ribose, phosphate, and a RNA base
RNA polymerase binds the single stranded mRNA together

12. Transcription
mRNA leaves the nucleus through pores in the nucleus and travels to the ribosome

13. Translation End of mRNA binds to the ribosome at the start codon
START CODON: AUG
Each set of 3 nucleotides on the mRNA= 1 codon

14. Translation tRNA is in the cytoplasm and contains:
The anticodon to the mRNA strand with the matching RNA nucleotides
A bonding site that is specific for an amino acid within the cytoplasm
tRNA will pick up the correct amino acid and take it to the ribosome to be used to build protein

15. Translation
As the mRNA moves along the ribosome, the corresponding tRNAs are drawn in.
The tRNA drop off their amino acids and a peptide bond forms between the amino acids
After dropping of the amino acid, the tRNA leaves the ribosome and goes to pick up more amino acids to continue the process

16. Translation
Ribosome moves down the mRNA one codon at a time, bringing in tRNAs to match. They drop off their AA until the stop codon is reached.
Once the stop codon is reached, the protein is released into the cytoplasm.

17. Helpful animations:

18. Identifying Amino Acid Chains
Each mRNA carries a code that calls for a specific amino acid.
The sequence of amino acids bond together to form proteins
Use a mRNA codon chart to name the different amino acids in the protein chain.
START: AUG (everything before that doesn’t matter!)