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History of Genetics

Gregor Mendel discovered the laws of inheritance in 1866 by studying traits in pea plants. In the early 1900s, chromosomes were observed under microscopes and shown to behave similarly to Mendel's hypothesized units of heredity. It was later determined that chromosomes, not traits themselves, are inherited. Major discoveries throughout the 20th century uncovered DNA as the genetic material, its double helix structure, gene regulation, transposable elements, DNA sequencing techniques, recombinant DNA technology, and the first cloned mammal and bacterial genome. These breakthroughs established the foundations of modern genetics.

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339 views2 pages

History of Genetics

Gregor Mendel discovered the laws of inheritance in 1866 by studying traits in pea plants. In the early 1900s, chromosomes were observed under microscopes and shown to behave similarly to Mendel's hypothesized units of heredity. It was later determined that chromosomes, not traits themselves, are inherited. Major discoveries throughout the 20th century uncovered DNA as the genetic material, its double helix structure, gene regulation, transposable elements, DNA sequencing techniques, recombinant DNA technology, and the first cloned mammal and bacterial genome. These breakthroughs established the foundations of modern genetics.

Uploaded by

Dianne Joy
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© © All Rights Reserved
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HISTORY OF GENETICS

In 1866, Gregor Mendel discovered independent assortment of traits, dominant and


recessive expression. Traits appear in pairs; separate independently in the gametes;
recombine in pairs, in offspring. (Today we know Mendel only studied unlinked traits:
on separate chromosomes, or so far apart that crossover frequency approached 50%).

1902 -- Walter Sutton and Theodore Boveri, using dyes synthesized by the German
organic chemistry industry, observed that "colored bodies" in cells behaved in ways
parallel to the hypothetical agents of heredity proposed by Mendel. These bodies were
called chromosomes.

1905 -- Nettie Stevens observed in Tenebrio beetles that all pairs of homologous
chromosomes are the same size, except for one pair which determines sex -- X, Y.

1909 -- Thomas H. Morgan correlates the X chromosome with sex-linked


inheritance of the white eye trait in Drosophila -- a strain of flies discovered by an
undergraduate lab assistant, cleaning out old bottles of flies in Morgan's lab. Morgan
went on to make many important discoveries in fly genetics and linkage analysis that
apply to all diploid organisms.

1941 -- Beadle and Tatum determined in Neurospora that each gene encodes one
product (protein). (Later, we learned that RNA can be a product, not always
transcribed to protein; for example, a ribosomal RNA.)

1944 -- Oswald Avery identified DNA as the genetic material. Pieces of DNA can
transfer genes into bacteria cells, and transform them genetically.

1953 -- Rosalind Franklin and Maurice Wilkins showed that DNA is a double
helix.

1953 -- James Watson and Francis Crick determined the structure of the base pairs
which enable replication producing two identical daughter helices.

1961 -- Jacob and Monod figured out regulation of the lac operon.

1960's -- Barbara McClintock discovered transposable elements in corn; later found


in bacteria and animals.

1970 -- Temin and Balitimore discovered reverse transcriptase in retroviruses; an


enzyme later used to clone genes based on the RNA encoding the product.
1977 -- Maxam, Gilbert, Sanger, et.al. -- developed methods to sequence DNA.

1981 -- The first transgenic mammals were made.

1987 -- Kary Mullis invented the polymerase chain reaction (PCR), using a
thermostable enzyme from a thermophilic bacterium discovered by Thomas Brock at
a geyser in Yellowstone. Mullis sold the process to a pharmaceutical company, and
earned very little. Brock didn't earn a cent.

1995 -- The first bacterial genome sequence, Haemophilus influenzae, was completely
determined.

1996 -- Ian Wilmut cloned the lamb Dolly from adult mammary gland tissue.

Source: Kenyon College, Biology Department // (biology.kenyon.edu)

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