1. Replication, Transcription
& Translation Notes
Unit 3

2. Replication Replication: the process of DNA copying itself
DNA needs to replicate before the cell can reproduce
Animation:

3. Replication steps
First step: enzymes “unzip” DNA into two separate strands
Each strand serves as a pattern to make new DNA molecules
Second step: free nucleotides join onto strands to form two new strands of DNA, aided by enzymes
Two complete strands will result, these will be exactly alike
Each resulting strand has one “old” half and one “new” half
Animation:

4. DNA Replication Occurs during S phase of Cell Cycle
Must occur prior to cell dividing

5. Helicase unzips double helix
DNA polymerase joins nucleotides

6. Resulting daughter cells (at conclusion of mitosis and cytokinesis) each have identical DNA

7. Transcription
DNA has specific instructions for making proteins (base sequence)
Protein synthesis happens at the ribosome
DNA cannot leave nucleus
DNA will unwind at particular area with specific protein instructions
mRNA will form with these instructions (this is transcription)

8. Transcription Produces mRNA from DNA
Genetic code (instructions from DNA) which will ultimately form specific protein
Segment of DNA unwinds & separates, revealing pattern for mRNA
The code obtained from DNA dictates which amino acids are needed
Codon= trio of nitrogen bases (1 codon 1 amino acid)
Protein = chain of amino acids

9. mRNA leaves nucleus
Travels to ribosome with “message” (instructions) for protein synthesis

10. mRNA arrives at ribosome with a series of codons (protein assembly instructions)

11. tRNA will respond with specific “anti-codons” (complementary base pair rules apply), bringing the corresponding amino acid to the ribosome

12. Translation
Conversion of RNA into amino acid sequence that makes a protein
The mRNA leaves the nucleus and enters the cytoplasm
Ribosomes attach to mRNA
tRNA picks up the correct amino acids and carries them to the mRNA strand forming the protein
Animation:

13. Translation
Process by which protein is actually formed as per original instructions from DNA
Occurs at the ribosome
Amino acids = building blocks of proteins
Proteins = polypeptides(macromolecules)
Sequence of aa determines protein

14. The Genetic Code

15. 4 Bases
64 possible combinations (codons)
20 amino acids

16. Review of Process (Animation)