DNA - The Molecule of Heredity

What are the incorrect historical theories of inheritance?

• Theory of pangenesis

• Theory of preformation

• Blending theory of inheritance

Homonculus

a “little man” that early microscopists thought they saw in sperm

What did Robert Brown do?

discovered the nucleus in plant cells

What did Friedrich Miescher do?

isolated nuclei from white blood cells in pus (discovered nuclein, now known as nucleic acid")

What did Walter Flemming do?

discovered chromosomes and chromatin (

• chromatin = stained nuclear material

• chromosome = colored body

What is chromatin made up of?

DNA (deoxyribonucleic acid) and proteins

What did Albrecht Kossel do?

identified the four nitrogenous bases

What did Phoebus Levene do?

• Determined DNA was made up of a sugar, a phosphate, and a nitrogenous base

What concluded from Levene’s experiment? (tetranucleotide experiment)

nucleottides are fixed in four base sequences consisting on all four bases

What did Walter Sutton and Theodore Boveri do?

They proposed the chromosomal theory of inheritance, which states genes are carried on chromosomes

What must genetic material contain?

a molecule with

1) Complex information
2) must be able to replicate

3) must be a transmissible trait

4) must vary

What did Fredrik Griffith do?

he discovered the transforming principle

What strains of bacteria did Griffith work with?

Streptococcus pneumonia, R strain and S strain

How did Griffith perform his experiment?

he used capsules to control their exposure and interactions with the immune systems

What did Avery, MacLeod and McCarty do?

they used chemical analysis and selective enzymes to identify the transforming principle of DNA

What is Protease?

an enzyme that destroys protein

What is RNase?

a enzyme that destroys RNA

What is DNase?

an enzyme that destroys DNA

What did Hershey & Chase do?

they used bacteriophages and radioactive isotopes to prove that DNA was the genetic material

What are bacteriophages?

viruses that infect bacteria

What is Chargaff’s party rule?

About the same number of A’s and T’s and about the same number of C’s and G’s

What are base pairs?

Adenine, Thymine, Guanine, Cytosine

What did Franklin and Wilkins do?

Provided crucial models from Franklin's X-ray diffraction work to conclude that DNA is a double helical structure

What did Watson and Crick do?

They used evidence from biochemistry and X-ray diffraction to build the correct DNA model that matched evidence