The Quest for the Gene Flashcards
Darwin Origin of Species
Organisms have a slightly different Traits, and this slight variation becomes more important over time, as environment change and some Traits become more useful than other
it is not the most intellectual of the species that survives; it is not the strongest that survives; but the species that survives is the one that is able best to adapt and adjust to the changing environment in which it finds itself.”
Darwins’s Pangenesis Theory
Pan = Prefix, “all”, “of everything”.
Genesis = The beginning of someting (origin)
Pangenesis is the mechanism proposed by Charles Darwin (1868) to explain heredity…, Pangenesis has been largely thought to be wrong…being now only of historical interest.”
Gregor Mendel – The Father of Genetics
Experiments inPlant Hybridization” (1865) Mendel hypothesized that each parent contributes some particulate matter to the offspring. He called this heritable substance “elementen’’
He Studied traits in English Peas that was transmissible.
The 7 traits he studied seemed to be inherited independently of each other, which made these traits really useful for doing Quantitative, or measurement-based, Biology
Gene
1.The functional and physical unit of heredity passed from parent to offspring.
2.Genes are pieces of DNA, and most genes contain the information for making a specific protein.
Chromosomes and The Boveri–Sutton chromosome theory of inheritance (genes in chromosomes)
In 1882, Walther Flemming published the definitive study of the cellular process of mitosis.
In 1902 - Boveri’s drawings of abnormalAscariscleavage divisions.
Already in his earlyAscariswork Boveri focused on abnormalities in division and drew upon them for understanding the mechanics of cell division. (A) DividingAscarisegg in which all of the chromosomes are in contact with only one aster. (B–D) Various examples of chromosomes being in contact with a single aster. (E) Abnormal spindle, contacting one chromosome pair only partially. (F,G) Dispermic eggs with an extra aster that does not contact chromosomes. (H) Tetrapolar mitosis of a dispermicAscarisegg.
Gene organization is not Random!
1915- The “Fly Boys” and Gene Linkage Maps
Genes are located on Chromosomes and they are organized in a linear way
Linkage mapping - conventional genetic mapping based on the idea that the farther apart two linked genes are, the more likely a recombination event between them will be.
Hermann Muller-How New Genes Appear?
In 1926 he discovered the origin of new genes by mutations, a theory first proposed in the early 1900
The Nobel Prize in Physiology or Medicine 1946 was awarded to Hermann Joseph Muller “for the discovery of the production of mutations by means of X-ray irradiation
Modern Synthesis
Basically, The Modern Synthesis uses Mendelian inheritance – Mendel’s Rules – to Explain how Darwinian Natural Selection works in real time
Griffith’s Experiment (1928) –
“Transforming Principle’’
Griffith studied Streptococcus pneumoniae and learned that a “transforming principle” can be transferred from dead virulent bacteria to living nonvirulent bacteria. Many investigators at that time believed that the transforming principle was protein
The Beadle – Tatum Experiment (1941)
Beadle and Tatum performed experiments that suggested:
“one gene codes for one enzyme.”*
*Enzymes are proteins that act as biological catalysts.
Induced mutation by Radiation Exposure.
Tested capability to grow in complete medium (Amino Acids + Vitamins) and minimal medium.
Avery, MacLeod, and McCarty Experiment (1944) –
DNA is the “Transforming Principle
Avery, MacLeod, and McCarty identified DNA as Griffith’s transforming principle. By adding enzymes that either destroy proteins (protease) or DNA (deoxyribonuclease or DNase) to bacteria that were broken apart to release their contents, the researchers demonstrated that DNA transforms bacteria—and that protein does not.
Chargaff Experiment (1950) –
In 1950, Chargaff discovered that the ratio of the nucleic acid bases, purines to pyrimidines (adenine to thymine, guanine to cytosine) was always 1:1. This observation provided strong evidence that the nucleic acid bases form complementary pairs within the DNA molecule.
Rosalind Franklin (1952) –
The DNA is a Helix
Photo 51: DNA X-ray diffraction image
This work revealed the helical structure and location of the phosphate sugar on DNA.
Watson and Crick (1953) –
The DNA is a Double Helix
Maurice Wilkins, Franklin’s colleague showed James Watson and Francis Crick Photo 51 without her knowledge. Watson and Crick used that image to develop their structural model of DNA. In 1962, after Franklin´s death, Watson, Crick, and Wilkins shared the Nobel Prize in Physiology or Medicine for their findings about DNA
