History of Genetics

History of DNA

Learning Objective

Understand the series of discoveries and scientific process that led to our modern day model of DNA.

In the mid to late 1800's two scientists were working towards the idea of evolution by means of natural selection. This idea cemented characteristics being passed generationally, and outside influences impacting future populations.

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1859

Natural Selection

Gregor Mendel discovered that traits are passed down via discrete units. Regardless if the traits seem to blend together, they remain discrete over generations.

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1865 Heredity

Isolates DNA for the first time in 1869, but calls in "nuclein".

​While working with white blood cells and extracts a molecule unknown. It was named after the nucleus.

Frederick Miescher

Observed the behavior of chromosomes during division and described the process of mitosis.

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Walter Flemming

​William Henry Bragg & William Lawrence Bragg

​Between 1912-1914 W.H. Bragg and his son W.L. Bragg discover that the structure of a crystal can be inferred through the patterns made when exposed to an x-ray. Each crystal will scatter the x-rays in a particular way based on their structure.

The next slides go with the Structure of DNA Discovery Map activity

Was highly skilled at x-ray crystallography and took a very clear photo of DNA now called "photo 51". This shape suggested the double helix.

Rosalind Franklin

Helped Rosalind Franklin

​perfect the x-ray crystallography method.

Maurice Wilkins

​Erwin Chargaff

Discovered that the amount of Adenine (A) is always equal to the amount of Thymine (T) and that the amount of Cytosine (C) is equal to the amount of Guanine G.

** You can write this somewhere else if you don't have room: Chargaff's Rule for frequency of base pairs

A=T

G=C

​Watson and Crick

​Developed the model that we use today. They developed the double helix structure. This structure looks like a twisted ladder that contains nitrogenous bases. They used the work of many scientists.

Open Ended

Given the learning objective, Understand the series of discoveries and scientific process that led to our modern day model of DNA, what are your key takeaways from today?