Bell Work

• A set of parents have 4 children. One is dominant, one is recessive, and two are heterozygous for a trait.

• What is the genotype of the parents?

Bell Work

• Who is “the father of genetics”?• Who came up with the double helix model?• Who did an experiment on fruit flies?• Who did an experiment on rats?

• Write these three questions on your bell work:– What are the chemical components of DNA?– What clues helped scientist solve the structure of

DNA?– What does the double-helix model tell us about

DNA?

Objectives

• Understand the historical discovery of DNA.• Know the chemical structures of DNA

including the effectiveness of the double helix.• Understand hydrogen bonding in regards to

base pairs.

History of DNA page 349.

• Gregor Mendel-1865– Father of Genetics– Showed that

characteristics in pea plants can be passed in a predictable way.

– In USA history: 13th amendment abolishing slavery was passed.

History of DNA page 349.

• Walter Sutton- 1903– First one to realize that

chromosomes hold genetic material.

– American geneticist

History of DNA page 349.

• Thomas Hunt Morgan– Showed that genes are arranged

linearly on the chromosomes of a fruit fly.

– Gene Linkage: pg. 328. some traits are closer together on the chromosome, so they are more likely to be inherited together.

– The closer two genes are to each other, the less likely they will be divided during crossing over.

History of DNA page 349.• Frederick Griffith- 1928

– Bacteria contain a molecule that can transfer genetic information from cell to cell.

– Pg. 339 figure 12-1– Transformation: one type of bacteria

(harmless) is permanently changed into another bacteria (disease causing).

– USA History- mickey mouse first appears. Herbert Hoover is President. 1929 the Great Depression happens.

History of DNA page 349.

• 1944- Oswald Avery, Colin Macleod, Maclyn McCarty– Discover that the nucleic acid DNA stores and

transmits genetic information from one generation to the next.

History of DNA page 349.

• Hershey-Chase-1952– Repeat the Avery

experiment and confirm the results. pg. 341 figure 12-3

– History: Elizabeth II becomes queen (like the current queen of England).

History of DNA page 349.

• Watson and Crick: 1953– Publish their model of DNA double helix.– Rosalind Franklin: purified DNA, stretched it

out and then X-ray beamed it. This gave her a diffraction photo of DNA.

– Watson and Crick were working on their double helix model when they say Franklins picture.

History of DNA page 349.

• They realized that their double helix model was correct and explained Chargaff’s rule – Chargaff’s Rule: there are an equal number of

Adenines and Thymines and guanines and cytosines in each DNA strand.

– Antiparallel- The DNA runs in opposite directions, ensuring that the nitrogenous bases are in the center of the cell.

History of DNA page 349.

• Craig Venter and Francis Collins: 2000– Draft of the human

genome DNA sequence.– The final verison was

published in 2003.