Molecular Biology: A Brief History

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Molecular Biology A Brief History

• Chapter 1

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Introduction-What is Molecular Biology?

• More than one definition
• Attempt to understand biological phenomena in
  molecular terms
• Makes molecular biology difficult to distinguish
  from biochemistry
• The study of gene structure and function at the
  molecular level
• More restrictive
• More useful
• Origins
• Grew out of genetics and biochemistry
• Early work on genes
• Not considered molecular biology/molecular
  genetics
• Early investigators didnt know molecular nature
  of genes
• Called transmission genetics
• Transmission of traits from parental organisms to
  offspring
• Chemical composition of genes not known until
  1944
• The beginning of molecular biology

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Transmission Genetics

• Started with Gregor Mendel-1865
• Before Mendel's research inheritance thought to
  be a blending of traits from the parents
• Mendel particulate
• Each parent contributes particles, or genetic
  units, to the offspring
• Particles now called GENES
• Made important generalizations on inheritance
  based on phenotype
• The observable characteristics
• Can also refer to the whole set of observable
  characteristics of an organism

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Transmission Genetics

• Mendels Laws of Inheritance
• Genes can exist in different forms called alleles
• One codes for yellow seeds, the other for green
• One dominant over the other
• Called recessive
• Yellow was dominant over green when crossed
• 1st filial generation had yellow seeds
• When F1 yellow peas were allowed to
  self-fertilize, some green-seeded peas reappeared
• Ration in the F2 generation very close to 31
• Conclusions reached by Mendel
• Each parent plant carried two copies of the
  gene-or parents were diploid
• . Homozygotes have two copies of the same allele
• Heterozygotes have one copy of each allele
• Also that the sex cells must have been haploid
  i.e., half the alleles

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