GENE EXPRESSION AND REGULATION.pptx

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1. GENE EXPRESSION AND REGULATION By:- AKANKSHA SINGH M.PHARM Ist YEAR

2. Introduction of gene expression Transcription Translation Regulation of gene expression Lac operon theory CONTENTS:

3. Gene expression is the process by which the information encoded in a gene is used to direct the assembly of a protein molecule. It is explored through a study of protein structure and function, Transcription and Translation. It is the process by which information from a gene is used in the synthesis of a functional gene product. GENE EXPRESSION

4. How its work- When genes are expressed, the genetic information (base sequence) on DNA is first copied to a molecule of mRNA (transcription). The mRNA molecules then leave the cell nucleus and enter the cytoplasm, where they participate in protein synthesis by specifying the particular amino acids that make up individual proteins (translation).

5. Genetic information , chemically determined by Dna structure is transferred to daughter cells by DNA replication and expressed by Transcription followed by Translation. This series of events is called “ Central Dogma” is found in all cells and proceeds in similar ways except in retroviruses which posses an enzyme reverse transcriptase which converts RNA into complementry DNA. The extended  central dogma of molecular biology  includes all the cellular processes involved in the flow of genetic information

6. Gene Expression contains main 2 steps; Transcription and Translation. Together , they are known as gene expression, During the process of transcription, the information stored in a gene’s DNA is passed to a similar molecule called RNA in the cell nucleus.

7. Transcription takes place in the nucleus. It uses DNA as a template to make an RNA (mRNA) molecule. During transcription, a strand of mRNA is made that is complementary to a strand of DNA. Transcription takes place in three steps: initiation, elongation, and termination. Step 1: Initiation Initiation  is the beginning of transcription. It occurs when the enzyme RNA polymerase binds to a region of a gene called the promoter. This signals the DNA to unwind so the enzyme can ‘‘read’’ the bases in one of the DNA strands. The enzyme is now ready to make a strand of mRNA with a complementary sequence of bases. TRANSCRIPTION

8. Step 2: Elongation Elongation  is the addition of nucleotides to the mRNA strand. RNA polymerase reads the unwound DNA strand and builds the mRNA molecule, using complementary base pairs. There is a brief time during this process when the newly formed RNA is bound to the unwound DNA. During this process, an adenine (A) in the DNA binds to an uracil (U) in the RNA. S tep 3: Termination Termination  is the ending of transcription, and occurs when RNA polymerase crosses a stop (termination) sequence in the gene. The mRNA strand is complete, and it detaches from DNA.

9. It is a process by which proteins are synthesized. Translation is a complex cellular process where mRNA molecules, ribosome, tRNA molecules, amino acids, energy sources ATP and GTP and a no. of factors act together in a highly coordinated way. Translation is the process in which ribosome in the cytoplasm or endoplasmic reticulum synthesize proteins after the process of transcription of DNA to RNA in the cell’s nucleus. TRANSLATION (Protein Synthesis)

10. Initiation:  Ribosomal subunits bind to mRNA. Elongation:  The  ribosome  moves along the mRNA molecule linking  amino acids  and forming a polypeptide chain. Termination:  The ribosome reaches a stop codon , which terminates protein synthesis and releases the ribosome. S tages of Translation in Protein Synthesis

11. Stimulates the expression of certain gene and inhibit that of others is called regulation of gene expression. The first discovered example of a gene regulation system was the lac operon , discovered by Jacques Monod , in which protein involved in lactose metabolism are expressed by E.coli only in the presence of lactose and absence of glucose. REGULATION OF GENE EXPRESSION :

12. Transcription Level (Formation of primary transcription). Processing of level (Regulation of splicing). Transport of mRNA from nucleus to the cytoplasm. Translation level. STEPS:-

13. Diagram showing at which stages in the DNA-mRNA-protein pathway expression can be controlled

14. POSITIVE REGULATION : When the expression of genetic information is quantitatively increased by the presence of specific regulatory element is known as positive regulation. it is known as activator or positive regulator. NEGATIVE REGULATION: When the expression of genetic information is diminised by the presence of specific regulatory element is known as negative regulation. its known as repressor. EXAMPLE OF GENE REGULTION: The lac operon is an intresting example of how gene expression can be regulated. TYPES OF REGULATION OF GENE

15. it helps in Lactose metabolism. Lac – lactose , glucose + galactose Operon – group of gene. Its expressed only when lactose is present & glucose is absent. The  lac operon is an  operon , or group of genes with a single promoter (transcribed as a single mRNA). The genes in the operon encode proteins that allow the bacteria to use lactose as an energy source. LAC OPERON

16. The  lac   operon contains three genes:  lacZ ,  lacY , and  lacA . These genes are transcribed as a single mRNA, under control of one promoter.   In addition to the three genes, the  lac   operon also contains a number of regulatory DNA sequences. These are regions of DNA to which particular regulatory proteins can bind, controlling transcription of the operon . Structure of the  lac   operon

17. P = promoter I = repressor \ initiation gene O= operator (where repressor attached) Z = 8- galactose (separate lactose) Y = permease (import lactose) a = Transacylase (function unknown)

18. The  promoter  is the binding site for RNA polymerase, the enzyme that performs transcription. The  operator  is a negative regulatory site bound by the  lac  repressor protein. The operator overlaps with the promoter, and when the  lac  repressor is bound, RNA polymerase cannot bind to the promoter and start transcription. The  lac  repressor The  lac  repressor is a protein that represses (inhibits) transcription of the  lac   operon . It does this by binding to the operator, which partially overlaps with the promoter. When bound, the  lac  repressor gets in RNA polymerase's way and keeps it from transcribing the operon . 

19. When lactose is not available, the  lac  repressor binds tightly to the operator, preventing transcription by RNA polymerase. However, when lactose is present, the  lac  repressor loses its ability to bind DNA. It floats off the operator, clearing the way for RNA polymerase to transcribe the operon .

20. This change in the  lac  repressor is caused by the small molecule  allolactose , an isomer (rearranged version) of lactose. When lactose is available, some molecules will be converted to allolactose inside the cell. Allolactose is an example of an  inducer , a small molecule that triggers expression of a gene or operon . The  lac   operon is considered an  inducible operon  because it is usually turned off (repressed), but can be turned on in the presence of the inducer allolactose .

21. https://courses.lumenlearning.com/suny-wmopen-biology1/chapter/regulation-of-gene-expression/ https://en.wikipedia.org/wiki/Regulation_of_gene_expression https://www.ncbi.nlm.nih.gov/books/NBK459456/ https://bioprinciples.biosci.gatech.edu/module-4-genes-and-genomes/4-7-gene-regulation/ REFERENCES

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