BIOLOGY: GENETICS

BIOLOGY: GENETICS

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Come On Let us dive into the ocean of General Science,


History of genetics research

• The father of genetics is Gregor Mendel (Austria-Hungary). In 1866 he published the principle known as Mendelian Inheritance which described the concept of inheritance between parent organisms and offspring
• In 1869 Friedrich Miescher (Switzerland) discovered DNA
• 1880: Walther Flemming (Germany) describes division of chromosomes
• 1933: Jean Brachet (Belgium) establishes DNA is found in chromosomes and RNA in cell cytoplasm
• 1944: Oswald Theodore Avery, Colin McLeod, Maclyn McCarty (US) identify DNA as genetic material
• 1953: James Watson and Francis Crick (US) establish double helix structure of DNA. They win the Nobel Prize in Physiology or Medicine in 1962 for this discovery
• 1968: Hargobind Khorana, Robert Holley and Marshall Nirenberg (US) demonstrate the role of RNA in protein synthesis. Nobel in Medicine 1968
• 1977: Frederick Sanger (UK) sequences DNA for the first time. He produce the entire genome of bacteriophage X174. Nobel in Chemistry in 1980
• 1983: Kary Mullis (US) discovers polymerace chain reaction enabling easy amplification of DNA. Nobel in Chemistry 1993
• 1995: The genome of Haemophilus influenzae is the first genome of a living organism to be sequenced
• 2001: First draft sequence of the human genome
• 2003: Human Genome Project successfully completed

DNA

• DNA (deoxyribonucleic acid) is the basis for genetic inheritance. However, certain viruses use RNA for genetic information
• DNA is composed of a chain of nucleotides. There are four types of nucleotides: adenine (A), cytosine (C), guanine (G), thymine (T)
• DNA usually exists in a double-helix structure molecule
• Each nucleotide in one strand of the double-helix pairs with a particular partner nucleotide in the other strand. A pairs with T and C pairs with G

Chromosome

• Genes are regions within DNA. Genes are arranged in long chains of DNA molecules. These chains are called chromosomes
• Eukaryotic organisms have DNA arranged in multiple such chromosomes. Bacteria have only one chromosome
• The combined DNA sequence of all chromosomes is called the genome. This contains all hereditary information of that organism
• Haploid organisms have only copy of each organism. Eg: male bees, wasps, ants
• Diploid organisms have two copies of each chromosome. Eg: most plants and animals (including humans). However, in male humans the sex-linked X and Y chromosomes exist only as a single copy.
• Male: XY, Female: XX

Human Genome Project

• The Human Genome Project was an international scientific effort to determine the complete genetic code of human beings
• Launched in 1990, complete results published in 2003
• Performed by scientists from US, UK, Canada and New Zealand, lead by University of California Santa Cruz
• Key findings of the project include
  • There are approximately 25000 genes in human beings
  • All human races are 99.99% alike genetically
  • Most genetic mutation occurs in male. Thus males are responsible for genetic evolution and for genetic disorders
• Human Genome Project mapped nucleotides in haploid sequences. Efforts are currently underway to map diploid sequences as well. Eg: International HapMap Project, Personal Genome Project

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JOHAR