Thursday, September 16, 2010
Friday, September 3, 2010
PowerPoint Presentation On Lord Krishna
Lord Krishna
On the occasion of janmastmi we have tried to show some moments of life of lord krishna.Download
Wednesday, September 1, 2010
PowerPoint Presentation On Gene Regulation
PPT On Molecular Mechanisms Of Gene Regulation
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Gene Regulation Presentation Transcript:
1. Transcription Regulation:Prokaryotes Transcription regulation is common mechanism in prokaryotes Negative Regulation = repressor binds to regulatory site to block transcription of active gene Positive Regulation = Activator binds to regulatory site to stimulate transcription; gene is off in absence of activator
2. Operon Model of Regulation
The operon consists of several structural genes required for lactose metabolism under the control of a single regulatory domain = coordinate regulation Repressor binding site = operator Site for transcriptional activation = promoter
3. Operon Model of Regulation
Inducible operon is activated by small molecule inducers; mode of regulation in degradative (catabolic) pathways Repressible operon is shut off by small molecule co-repressors; mode of regulation in biosynthetic (anabolic) pathways
4. Gene Regulation Mechanisms
Negative regulation: repressor protein blocks transcription: Inducible: inducer antagonizes repressor to allow transcription initiation Repressible: aporepessor combines with co-repressor to form functional repressor
5. Gene Regulation Mechanisms
Positive Regulation: transcription occurs only if promoter is activated by transcriptional activator Negative regulation is more common in prokaryotes Positive regulation is more common in eukaryotes Autoregulation: protein regulates its own transcription
6. Lac Operon
Lactose degradation is regulated by the lactose (lac) operon The first regulatory mutations discovered affect lactose metabolism Structural proteins of the lac operon: B- galactosidase required for lactose metabolism and lactose permease required for lactose entry
7. Lac Operon
Lac operon gene expression can be inducible or constitutive The repressor is expressed constitutively (continuously) from the i gene and binds to the operator to block transcription The operon is inducible since lactose binds and inactivates the repressor to permit transcription initiation
8. Lac Operon
Lactose operator is essential site for repression Operator mutations are cis-dominant because only genes on the same genetic unit are affected Lactose promoter is essential site for transcription Lac operon contains linked structural genes and regulatory sites
9. Lac Operon
Lactose operon is also subject to positive regulation Positive regulation of the lac operon involves cAMP-CRP ( cyclic AMP receptor protein) which binds to the promoter to activate transcription by RNA polymerase cAMP-CRP complex regulates the activity of the lac operon
10. For more please refer our PPT. Thanks.
PowerPoint Presentation On Gene Expression
PPT On Gene Expression
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Gene Expression Presentation Transcript:
1. Gene is basic unit of heredity and is a segment for genomic information.
It consist of both ‘coding’ and ‘non-coding’ sequences.
These coding and non-coding sequences are copied in a process called Transcription producing RNA which directs the synthesis of proteins.
Phenotype of an organism is an resultant of genes interacting with each other.
Every cell has same set of genes so it is necessary to have a mechanism which allows desired gene to function at particular time.
Expression of gene is not a single step process rather a vast system comprising a complex network.
Activity of undesired genes has to be restricted which requires time and space.2. Operon Negative control of lactose operon Positive control of lactose operon Mutation experiments by Jacob and Monod
3. F. Jacob and J. Monod in 1961 proposed a model to explain induction or repression of enzyme synthesis. This model is known as ‘Operon Model’ which assumes presence of coordinated control of protein synthesis and this unit is called ‘Operon’. Operon is a group of linked genes linked on chromosome under control of promoter and these linked genes gives rise to a single m-RNA. Operon consists of:- An operator gene which control activity Structural gene which participates in protein synthesis.
4. Histidine operon(his operon)- it has RNA element. Tryptophan operon(trp operon)- a repressible system which controls biosynthesis of tryptophan from precursor chorismic acid. Lactose operon(lac operon)- regulated by factors including presence of glucose and lactose.
5. An operon required for transport and metabolism of lactose in E.coli. E.coli cells when transferred to medium containing lactose instead of glucose, they stop growing for a certain period of time. They again starts growing as during lag phase cells turn on lac operon. Galactoside permease is the enzyme used for transport of lactose within cells. Lactose is made up of glucose and galactose linked by β-galactosidic bond. Three genes encoding above mentioned enzymes are: Lac Z- encodes for β galactosidase Lac Y- encodes for galactoside permease Lac A- encodes for galactoside transacetylase
6. It is lac repressor coded by a gene called gene 1(lac 1). Repressor occupies operator and blocks access of RNA polymerase which in turn cannot transcribe lac Z, Y and A genes. Lac operon is repressed till glucose is available. In presence of lactose operon is turned on so that lactose can be metabolized. Repressor is an allosteric protein which changes its confirmation when it binds to small molecules. Inducer binds to repressor which is an alternate form of lactose called allolactose. Allolactose is glucose linked to galactose by β- 1,6 bond.
7. Allolactose acts as inducer by binding to repressor causing conformational shift. When repressor is , RNA polymerase is free to bind to lac promoter. It then transcribe three structural genes i.e. lac Z, lac A, lac Y.
8. E.coli cells metabolize glucose easily as compared to lactose Selection of glucose among other energy sources is influenced due to some breakdown products. It is thus called as Catabolite Repression. A nucleotide called cyclic AMP (cAMP) responds to glucose concentration. Its concentration responds inversely proportional to glucose concentration.
9. Positive controller is a complex comprising of two parts: cAMP Binding protein CAP (catabolite activator protein) Complex binds to promoter and turns it on by binding RNA polymerase Complex when binds, it causes promoter to bend and makes easier the DNA strands forming open promoter complex.
10. For more please refer our PPT. Thanks.
PowerPoint Presentation on History of Genetic Engineering
PPT On Genetic Engineering
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History of Genetic Engineering Presentation Transcript:
1. Genetic engineering is normally taken to mean recombinant DNA technology -- the artificial addition, deletion or rearrangement of sequences of bases in DNA in order to alter the observable form and function of an organism. However, genetic engineering is sometimes referred to as biotechnology and biotechnologists have been quick to point out that mankind has been doing biotechnology ever since the first farmers some 10,000 years ago started to domesticate wild species by selecting seeds of wild plants for cultivation or selectively breeding wild animals. In this history, therefore, we include any artificial intervention in the reproductive process as well as some landmarks in the development of genetics which has made genetic engineering possible. This will include selection procedures old and new which could influence the genetic outcome of a reproductive event, gene therapy and diagnosis as well as cloning, vegetative reproduction and in vitro (test-tube) reproduction procedures.2. circa 10,000 years ago The beginnings of agriculture: selection of wild grasses and subsequent breeding in cultivation to form the precursors of modern staples such as wheat, rice and maize. A considerable practical knowledge was developed by breeders over the centuries and selection procedures often achieved from a single wild species a huge difference in form and function: e.g. the Great Dane and Chihuahua dog varieties from the wolf. Furthermore, 'unnatural' hybrids -- i.e. creating breeds across species barriers -- were made in ancient times. For instance the mule, a cross between a jackass or male donkey and a mare has been used as a pack animal in Europe for at least 3,000 years.
3. 1627 Francis Bacon foretells genetic engineering and terminator technology.
4. 1859 Charles Darwin published the first edition of The Origin of the Species which amongst other things gives extensive information on the knowledge of breeding at that time. Download The Origin of the Species from either of the two sites below:
5. 1865 Gregor Mendel's publication of his discoveries with the breeding of peas which became the foundation of modern genetics. MendelWeb - Origins of classical genetics. 1866 Ernst Haeckel proposes that the cell nucleus is the bearer of an organism's heritable characteristics. 1869 Friedrich Miescher discovers nuclein -- a major component of which is DNA -- in the cell nucleus.
6. 1875 Oscar Hertwig using microscopy observes sea urchin sperm entering the egg and the two nuclei fusing. 1890 Birth of a rabbit from an embryo implanted in the uterus of a surrogate. 1900 Hugo de Vries, Carl Correns & Erich von Tschermak rediscover Mendel's principles.
7. 1902 Walter Sutton & Theodor Boveri propose the chromosome theory of inheritance. Archibald Garrod suggested from studies of alcaptonuria, a disease for which one symptom is the appearance of a black pigment in the urine, that a defective gene gave rise to a defective enzyme (a protein which is a biological catalyst in cell processes). 1910 T. H. Morgan demonstrated that the chromosomes are the concrete entities which carry the genes. (Also Clavin Bridges, 1916) 1913 A.H. Sturtevant constructed a genetic map.
8. 1927 H. J. Muller demonstrated that genetic mutation could be induced by X-rays.
9. 1931 Barbara McClintock and Harriet Creighton demonstrate direct physical recombination by examining maize chromosomes microscopically.
10. For more please refer our PPT. Thanks.
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