1. Chapter – 10 Part II Molecular Biology of the Gene - Genetic Transcription and Translation

2. The Structure of Proteins Made up of amino acids There are 20 amino acids involved in protein synthesis Amino acids combine together to form the peptide linkage (link between amino group of one amino acid with the carboxyl group of adjacent amino acid) Many peptide linkages form a polypeptide chain Polypeptide chains fold to form a protein.

3. The Structure of Proteins

4. Stages of protein synthesis Two major stages involved: The first stage is called transcription –The 2 strands of the DNA molecule unwind and mRNA copies the genetic code (letters A, C, G and T) from DNA, the master molecule.

5. Stages of protein synthesis mRNA then comes out from the nucleus to cytoplasm The second stage is called translation –mRNA and tRNA (carrying amino acids) reach the cytoplasmic ribosome (composed of two protein subunits and rRNA) where the mRNA code is used to assemble amino acids –These amino acid chains elongate and fold to form proteins.

6. Protein Synthesis Summary: The process of copying DNA into RNA is called transcription and the Process of assembling proteins from RNA instructions is called translation

7. Transcription

8. Triplet Code Three mRNA bases code for a specific amino acid is called code / codon ( three nucleotides).

9. Triplet Code Three mRNA bases code for a specific amino acid is called code / codon ( three nucleotides).

10. Translation mRNA (carrying instructions for sequence of amino acid in a protein) comes out of the nucleus and reaches the cytoplasm to the site of ribosome, the location of protein synthesis. rRNA a structural component of ribosome

11. Translation tRNA (translator molecule) –Anticodon of tRNA attracts a specific amino acid –tRNA matches the codon in the mRNA –Part of the tRNA binds an amino acid and the other end has three nucleotides, anticodon that forms a base pair with the codon in the mRNA) –Amino acids of neighboring tRNA’s link to form the polypeptide chains. –Lengthened amino acid chains fold to form the protein molecule.

13. Types of RNA

14. Translation

15. Steps in Translation mRNA binds to the small subunit of the ribosome. Start codon AUG, brings in initiator tRNA with the amino acid methionine, and then large subunit binds. tRNA that matches the next codon brings in the appropriate amino acid in to the “A” site.

16. Steps in Translation Then the ribosome joins the mRNA to the next codon, moving the newly formed peptide to the “P” site. This continues until a stop codon is reached. At the stop codon, no new tRNA comes into the “A” site and the whole complex falls apart, releasing the new protein.

17. Steps in Translation

18. Editing out Genetic Material Intron is a segment of DNA, (or the mRNA transcript complementary to it), that does not encode information for the sequence of amino acids in protein. Exon is the segment of DNA or mRNA,that encodes information for the sequencing of amino acids in protein. A segment of DNA that makes transcript is called gene Genome size for human is 3 billion.