The brief history of molecular biology


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its my university task to make a assignment on the brief history of molecular biology i am sure i done it quite well by linking all the information to molecular

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The brief history of molecular biology

  1. 1. SP13-bty-001 Zohaib Hussain Molecular Biology The Brief History Of Molecular Biology Introduction: The first step which leads towards the development of field of biology is the use of microscope. Scientist searches the features of biology of living things by manipulating it. The main component of every living thing is a CELL (a basic unit of life) and renowned discove ry of cell is done by the Robert Hooke Background of molecular biology: Before studying history in details we need to know what molecular biology is. “It is the study of gene structure and function at molecular level” Molecular biology history is studied in two broad perspectives  Study of genetics  Study of biochemistry Both of the above fields comprised the molecular biology in it (A hybrid discipline). Early history: The first concept rise in the mind of people about inheritance is called as blending concept also called as a blending inheritance. People of the 17th century and early 18th century believes in a blending concept which is that t he offspring results after the cross is the mixture of the 2 parents i.e. a blending of each trait of parents in the offspring The Greg or Mendel discover his findings about the inheritance after examining the inheritance in 7 different traits of garden pea ( Pisum sativum ).Mendel proposed the laws of inheritance . He concludes that each parent contributes a particle or genetic unit to the offspring. e.g In the cross of yellow pea and green peas: a yellow parent contributes a gamete with a gene f or yellow seeds and the green parent a gamete with a gene for green seeds therefore all the F1 generation got one allele for yellow seeds and one allele for green seeds . they had not lost allele for green seed at all , but because yellow is dominant , all the seeds were yellow, however when these homozygous seed were well fertilized , they produced gametes containing allele for yello w and green color in equal in numbers and this allow green phenotype to reappear.
  2. 2. SP13-bty-001 Zohaib Hussain Molecular Biology The study of Mendel gives a concept about allele, dominant, recessive, homozygote, heterozygote, monohybrid and dihybrid. Mendel didn’t know about gene, chromosomes but his concept leads towards its role in the genet ics Mendel works is called as a particulate theory or transmission genetics Rediscovery of Mendel work: Mendel work is not uniformly accepted it is rejected uniformly because of an old blending concept and secondly people were unfamiliar of Mendel work too In the early 19th century 3 scientist rediscover Mendel work and accepted it because of the follow ing reasons  Nature of chromosome revealing is according to Mendel work  The concept that gamete contain only one allele i.e n number of chromosome Three botanists - Hugo DeVries, Carl Correns and Erich von Tschermak - independently redisco vered Mendel's work in the same year, a generation after Mendel published his papers. They help ed expand awareness of the Mendelian laws of inheritance in the scientific world. The three Europeans, unknown to each other, were working on different plant hybrids when they each worked out the laws of inheritance. When they reviewed the literature before publishing th eir own results, they were startled to find Mendel's old papers spelling out those laws in detail. Each man announced Mendel's discoveries and his own work as confirmation of them. The Fruit Fly Scientist work Morgan wanted to understand heredity and mutation, which is genetic change. At Columbia University Morgan established the famous "fly room." The Drosophila melanogaster, or fruit fly , is a good genetic research subject because it can be bred cheaply and reproduces quickly. Morg an was not the first to use the fruit fly as a subject, but his innovation and success popularized its use. Simple in design and easy to conduct, his early experiments are classics in genetics. By painstakingly examining thousands upon thousands of flies with a microscope and a magnifyi ng glass, Morgan and his colleagues confirmed the chromosomal theory of inheritance: that genes are located on chromosomes like beads on a string, and that some genes are linked (meani ng they are on the same chromosome and always inherited together) The concept of mutant, wild type, sex linkage, autosomes and sex chromosome are introduced.
  3. 3. SP13-bty-001 Zohaib Hussain Molecular Biology Recombination and genetic mapping: One of his students, in 1913 Alfred Sturtevant, created the first ever genetic map, a landmark e vent in genetics, he also discovered the genetic mapping techniques still used. Morgan concludes that genes are arranged in a linear fashion on the chromosome like beads on a string. This together with his awareness of recombination led him to proposed that the farther apart two genes are on the chromosome; the more likely they are to recombine. So more chances of crossing over in a widely spaced genes. The other scientist e.g. Barbara, Harriet, curt stern, discover the phenomenon of recombination in maize drosophila etc The above studies tell us about the transmission of genes and mapping of gene too but still scientist didn’t know how gene work and what are they made off. The milestone in molecular history discovery of DNA In 1869 Friedrich Miescher discovered DNA he called it “nuclein” and tells that it is composed of carbon nitrogen phosphorus and hydrogen .It would be years before the role of nucleic acids w ere recognized. Miescher, himself, believed that proteins were the molecules of heredity. However, Miescher laid the groundwork for the molecular discoveries that followed. Rosald avery in 1944 suggested that DNA is a transformation source as indicated in the Griffith experiment the chemical nature of transforming agent in the mouse strain causing death is DNA George beadle and E l Tatum prove the relationship between the gene and enzyme revealing the Garrod work1900 that alkaptonaria is caused due to abnormal buildup of an intermediate compound in your biochemical pathway which are catalyzed by proteins called enzymes . a defective gene give rise to a defective enzyme. In other words gene some to be a responsible for a making one enzyme. This was the one gene / one enzyme hypothesis. Hypothesis leads to false because most genes contain the information for making one polypeptide. How genes are replicated. Production of RNA and Proteins? The 3D structure Of DNA is discovered James Watson and crick 1953 based on the physical and chemical data that he collected n the laboratories primarily on the X ray diffraction data
  4. 4. SP13-bty-001 Zohaib Hussain Molecular Biology collected by Rosalind Franklin and Maurice Wilkins In 1958 Mathew Meselson and Franklin stahl proved the DNA replication in bacteria following semi conservative model . 1956 Francis Crick and George Gamov worked out the "Central Dogma" to explain protein synthesis from DNA: the DNA sequence codes for amino acid sequences and genetic information flows in one direction - from DNA to mRNA to protein Genes expression is the process by which a gene product (an RNA or a polypeptide) is made it’s a two steps process called transcription and translation are required to make a polypeptide fro m the instruction in a DNA gene According to crick each ribosome is responsible for the production of making only one protein but later on francious Jacob and Sydney Brenner give idea that ribosome’s can make a unlimited number of different proteins according to instruction in the mRNA that visit the ribosome’s this idea is proved correct in later stages Now question arises which parts of gene encodes a amino acid sequence? Marscall Nirenberg and Gobind khorana working independently with different concepts revea l the code in the early 1960s they found that 3 bases constitute a code word called a Codon that stands for one amino acids. Out of the 64 possible 3-base Codons, 61 specify amino acids the ot her 3 are stop signals Later advancements in molecular biology: 1. (1970) Howard Temin and David Baltimore independently isolated reverse transcriptase, an enzyme that can make DNA from RNA 2. (1972) Paul Berg used a restriction enzyme to cut DNA and ligase to past two DNA stran ds together to form hybrid circular molecule. This was the first recombinant DNA mole cule 3. (1977)Bacteriophage FX-174 (5368 bp) was the first complete genome (DNA) to be sequ enced
  5. 5. SP13-bty-001 Zohaib Hussain Molecular Biology 4. (1990) Human Genome Project launched: estimated cost of $13 billion (plan 15 years) 5. Yeast and E. coli genome completely sequenced . Patrick Brown of Stanford University presented the 'gene chip' containing 6116 different gene specific sequences of the yeast g enome . Ian Wilmut at Scotland's Roslin Institute presented"Dolly", a sheep cloned from the cell of an adult mammary gland 6. (1999) Drosophila melanogaster (fruitfly) genome completely sequenced (175 Mb) Future plans of molecular biology  Completion of the 2010 Project: the understanding the function of all genes within their cellular, organismal and evolutionary context of Arabidopsis thaliana  Completion of the first computational model of a complete cell, or maybe even already of a complete organism