1. Historical Timeline of Genetics
10th Grade Biology
Mr. Walker

2. Genetics is the scientific study of heredity and hereditary variation.

3. Gregor Johann Mendel
1865, began breeding garden peas at an Austrian monastery.
He introduced the idea of genetic traits, alleles, hybridization, and the law of segregation.

4. 1842-1910, Karl Wilhelm von Nageli and Walther Flemming discovered the nature of chromosomes.

5. Fredrick Griffeth Discovered “transformation”.
Used a bacteria to demonstrate that DNA can transform a avirulent living bacteria into a virulent one.

6. Avery, MacLeod, and McCarthy
1944, Used protein enzymes to show that DNA carried genetic information.
Many people didn’t believe it. They believed proteins were better candidates.

7. The Hershey Chase Experiment
1950, Alfred Hershey and Martha Chase finally, proved to skeptics that DNA contained the genetic materials.

8. Rosalind Franklin
1952, Franklin was the X-ray crystallographer who took the photo that enabled Watson and Crick to deduce the double helix structure of DNA.
She died of cancer at the age of 38. Her colleague, Maurice Wilkins, received the Nobel Prize in 1962 along with Watson and Crick.

9. 1953, James Watson and Francis Crick discovered the structure of DNA.

10. Heredity Notes: Humans have 23 pairs of chromosomes totaling 46.
Heredity is the passing of traits from parents to offspring
Alleles are different forms of a trait that a gene may have
Genetics is the study of how the traits are inherited
A hybrid is an organism that is produced from two different species. E.g. Liger

11. Hybrid Example

12. Important Terms
Dominant= a trait that covers up another trait. Capitalized letters are used to represent dominant traits.
Recessive=a trait that is being covered up by another trait. Lower case letters are used to represent recessive traits.
Punnett Squares are tools that predict the probability of traits in organisms
Genotype: the genetic makeup of an organism. E.g. Aa
Phenotype: the outward appearance of an organism. E.g. brown hair.
Homozygous: an organism with two alleles that are the same for a trait.
Heterozygous: an organism with two different alleles for a trait.

13. How to do a Punnett Square
-Use easily recognizable letters Rr. Aa. Not Cc
B- means BB or Bb
Other terms:
Hybrid-Heterozyous
Pure-homozygous
Example of Punnett Square and using two letters.