The Development of Genetics as a Science

6,000 years

Record of pedigrees of some domesticated animals and some crop plants were kept

Domesticated animals

Horses, dogs, camels, sheep, and others

Cultivated plants

Wheat, rice, maize-corn, date palm, and other herbal plants.

Hippocrates

Male seed is thicker or more solid while the female is more fluid.

Aristotle

The vital heat fluid; Semen was regarded as highly purified blood.

Semen

The vital heat fluid

Semen

Was regarded as highly purified blood.

Pythagoras

Vapors were from various organs unite to form individuals.

Vapors

Where various organs unite to form individuals.

Jan Swammerdam

He theorized that sex cells contain a complete miniatures of an adult, perfect in every form called a homunculus.

Homunculus

Theorized by Swammerdam, sex cells contain a complete miniatures of an adult, perfect in every form.

William Harvey

An organism is derived from substances present in the egg that differentiate into adult structure during embryonic development.

Casper Wolff

Disapproved the Theory of Preformation. Offered experimental evidence that no preformed embryo existed in the egg of the chicken.

Pierre Louis Maupertuis

Proposed that minute particles, one from each body, united in sexual reproduction to form a new individual.

Charles Darwin

Noted that each part of the body produced minute particles “gemmules” or “pangenes” which were contained in the blood of the entire body but eventually concentrated in the reproductive organs.

The Theory of Pangenesis

The body produced minute particles “gemmules” or “pangenes” which were contained in the blood of the entire body but eventually concentrated in the reproductive organs.

Blending

An individual represents of both parents and acquired characters would be inherited too.

August Weismann

Disapproved the Theory if Pangenesis. His experiment was the 22nd generation of mice where the tails of the parents were cut. Need to prove The absence of tails to offspring.

Gregor Mendel

Father of Modern Genetics, Has four postulates.

Friedrich Miescher

Identified DNA as an acidic substance found in cell nuclei.

Nuclein

First term for DNA

William Bateson

Coined the word “genetics”

Wilhelm Johanssen

First experiments on quantitative traits in broad beans.

Herman Nilsson-Ehle

First experiments on quantitative traits in wheat.

Thomas Morgan

Conducted the experiments on Drosophila (fruit flies). Genes are carried on chromosomes and the mechanical basis for heredity.

Eugenics Movement

Popular, fueling racist sentiment and leading to involuntary sterilization laws.

1910-1930

Eugenics Movement year

Karl Landsteiner

ABO Blood Types

Genetic Recombination (1931)

Caused by a physical exchange of chromosomal pieces.

Harriet Creighton and Barbara Mcclintock

Genetic Recombination is cased by a physical exchange of chromosomal pieces as shown in corn.

Beadle and Tatum (1941)

One gene encodes one protein.

Erwin Chargaff (1950)

In DNA, there are equal amounts of A and T, and equal amounts of C and G. However, the A+T to C+G ratio can differ between organisms.

Alfred Hershey and Martha Chase (1952)

DNA is the molecules that mediates heredity, as shown in bacteriophage labeling experiments.

Watson and Crick (1953)

DNA is in the shape of a double helix with antiparallel nucleotide chains and specific base paring.

Meselson and Stahl (1958)

DNA replication is semi-conservative, as shown using equilibrium density gradient centrifugation.

Hamilton Smith (1970)

The first restriction enzyme is purified.

Cohen and Boyer (1972-1973)

Recombinant DNA is first constructed.

Fred Sanger (1977)

DNA sequencing technology is developed.

1990

Genome projects begun

1996

The yeast genome complete

1998

The C. elegans genomes don

Pat Brown and colleagues (1990)

DNA microarrays are invented

1990

DNA fingerprinting, gene therapy, and genetically modified food come onto the scene.

1995

Automated sequencing technology allows genome to accelerate.

Ian Wilmut and colleagues (1996-1997)

The first cloning of a mammal from the Roslin Institute in Scotland.

Dolly the sheep

First cloned mammal

2000

Drosophila genome is completed. The Arabidopsis genome is completed. The human genome is reported to be completed.

2001

The sequence of the human genome is released and the “post-genomic era” begins.

2009

Controversies continue over human and animal cloning, research on stem cells, and genetic modification of crops.