1. Gene Expression Overview

2. Gene Expression
The Gene Structure
Protein Synthesis

3. Gene Expression
Gene expression is the process by which the information contained in a gene is converted into the structures and functions of a cell by producing a biologically functional protein.

4. Eukaryotic Cell

5. Gene Structure
Eukaryotic gene structure: Most eukaryotic genes in contrast to typical bacterial genes, the coding sequence (exons) are interrupted by noncoding DNA (introns).
The gene must have
( Exon; start signals; stop signals; regulatory control elements).

6. Protein Synthesis
Protein Synthesis is the process in which cells build proteins from information in a DNA gene in a two major steps:
I-Transcription and
II-Translation
Transcription : synthesis of an RNA (mRNA) that is complementary to one of the strands of DNA.
Translation : ribosomes read a messenger RNA and make protein according to its instruction.

7. Protein Synthesis

8. Transcription

9. Transcription
RNA polymerase copies both the exons and the introns. The stretch of DNA that is transcribed into an RNA molecule is called a transcription unit.
A transcription unit that is translated into protein contains coding sequence that is translated into protein and sequences that direct and regulate protein synthesis;
Transcription proceeds in the 5' → 3' direction.

10. RNA Splicing

11. Translation

12. Translation
Translation is the process by which ribosomes read the genetic message in the mRNA and produce a protein product according to the message's instruction.

13. Ribosomes are the site of protein biosynthesis using the mRNA as a template, the ribosome traverses each codon of the mRNA, pairing it with the appropriate amino acid. This is done using molecules of transfer RNA (tRNA) containing a complementary anticodon on one end and the appropriate amino acid on the other.

14. Elongation
Transfer of proper aminoacyl-tRNA from cytoplasm to A-site of ribosome;
Peptide bond formation; Peptidyl transferase forms a peptide bonds between the amino acid in the P site and the newly arrived aminoacyl tRNA in the A site. This lengthens the peptide by one amino acids.

15. Elongation
Translocation; translocation of the new peptidyl t-RNA with its mRNA codon in the A site into the free P site occurs Now the A site is free for another cycle of aminoacyl t-RNA codon recognition and elongation. Each translocation events moves mRNA , one codon length through the ribosomes.

16. Protein Synthesis

17. Reading the instruction means translating the code in the RNA from bases
(building block of DNA and RNA) to amino acids (building block of proteins).
Protein Synthesis