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RNA Processing in Devlopmental biology
- 3. Presented by: Sanya Yaseen 4010 Presented to: Sir Danish Riaz
- 4. RNA Processing (in cellular Differenciation) Topic
- 5. Introduction Overview of Gene Expression RNA processing in Eukaryotes RNA Selection RNA splicing Families of Proteins Sex determination in Drosophilla Contents
- 6. What is Cellular Differenciation? “Embryonic differentiation is the process of development during which embryonic cells specialize and diverse tissue structures arise.”
- 7. What is RNA Processing? “ The process of gene expression to form a specific protein at a specific place by the process of Translation”.
- 8. AN OVERVIEW OF GENE EXPRESSION The Different Cell Types of a Multicellular Organism Contain the Same DNA. Different Cell Types Produce Different Sets of Proteins. A Cell Can Change the Expression of Its Genes in Response to External Signals. Gene Expression Can Be Regulated at Many of the Steps in the Pathway from DNA to RNA to Protein.
- 9. AN OVERVIEW OF GENE EXPRESSION The Different Cell Types of a Multicellular Organism Contain the Same DNA. Different Cell Types Produce Different Sets of Proteins. A Cell Can Change the Expression of Its Genes in Response to External Signals. Gene Expression Can Be Regulated at Many of the Steps in the Pathway from DNA to RNA to Protein.
- 10. cells have ability to change genes expression without altering the nucleotide sequence of their DNA. If DNA were altered irreversibly during development, differentiated cell would be incapable of guiding the development of the whole organism. To test this idea, a nucleus from a skin cell of an adult frog was injected into a frog egg whose own nucleus had been removed. the egg developed normally into a tadpole, showing the normal expression of genes.
- 13. AN OVERVIEW OF GENE EXPRESSION The Different Cell Types of a Multicellular Organism Contain the Same DNA. Different Cell Types Produce Different Sets of Proteins. A Cell Can Change the Expression of Its Genes in Response to External Signals. Gene Expression Can Be Regulated at Many of the Steps in the Pathway from DNA to RNA to Protein.
- 14. o many proteins are common to all the cells e.g. structural proteins of chromosomes, RNA polymerases, DNA repair enzymes, ribosomal proteins, enzymes involved in glycolysis, cytoskelton proteins.
- 15. Diferent cell types produce specialized proteins: e.g. Heamoglobin only produced by reticulocytes a typical differentiated human cell expresses perhaps 5000–15,000 genes. large variations seen in the size, shape, behavior, and function of differentiated cells.
- 16. AN OVERVIEW OF GENE EXPRESSION The Different Cell Types of a Multicellular Organism Contain the Same DNA. Different Cell Types Produce Different Sets of Proteins. A Cell Can Change the Expression of Its Genes in Response to External Signals. Gene Expression Can Be Regulated at Many of the Steps in the Pathway from DNA to RNA to Protein.
- 17. Cabability to change the Gene Expression due to External Cues. e.g. Effect of Glucocortocoid Hormone on Liver cells. While some other cells of body do not effected by that hormone e.g. fat cells illustrate a general feature of cell specialization
- 18. AN OVERVIEW OF GENE EXPRESSION The Different Cell Types of a Multicellular Organism Contain the Same DNA. Different Cell Types Produce Different Sets of Proteins. A Cell Can Change the Expression of Its Genes in Response to External Signals. Gene Expression Can Be Regulated at Many of the Steps in the Pathway from DNA to RNA to Protein.
- 19. To become an active protein, the RNA must be: (1) processed into a messenger RNA by the removal of introns, (2) translocated from the nucleus to the cytoplasm, (3) translated by the protein-synthesizing apparatus (4) must be posttranslationally modified to become active. • Regulation can occur at any of these steps during development
- 21. Processing in Eukaryotes O Two Major Ways include:- censoring (RNA Selection) RNA Splicing Censoring:- Nuclear transcripts into mRNA RNA Splicing:- splicing of the mRNA into different proteins by using different combinations of potential exons.
- 23. RNA Selection ۞ mRNA transcript from pre-mRNA (nuclear RNA (nRNA) ۞ Pre-mRNA is transcribed from DNA ۞ Pre-mRNA contains introns which are spliced during its movement from nucleus to cytoplsm. ۞ Un-necessary segments are deleted ۞ More genes are transcribed in the nucleus than are allowed to become mRNAs in the cytoplasm.
- 24. Analysis on the transcripts from the CyIIIa genes of the sea urchin ๏ Encode calcium-binding and actin proteins, expressed only in a particular part of the ectoderm of the sea urchin larva. ๏ Trancribed not in ectoderm but also meso & endoderm but only effective in ectoderm of Sea Urchin Larva. ๏ Unprocessed genes are degraded in meso & endoderm.
- 25. RNA Splicing nRNA contains short exons (averaging about 140 bases) & large introns. By splicing together, different axons form different proteins. What is an intron in one cell's nucleus may be an exon in another cell's nucleus. Splicing of RNA is followed by these steps: 1. 5’ capping 2. polyadenyl tail 3. removal of introns 4. editing
- 26. 5’ Capping
- 27. Polyadenyl Tail
- 29. Editing of mRNA
- 31. Families of Proteins • Deletion of different exons in different cells forms different families of proteins. • Instead of one gene-one polypeptide, one can have one gene-one family of proteins. • for example:- α-tropomyosin gene to encode brain, liver, skeletal muscle, smooth muscle, and fibroblast forms of this protein. • These are called Splicing isoforms.
- 33. Sex determination in Drosophilla