1. Chapter 12: Molecular Genetics

2. For years, scientists were trying to figure out if DNA or proteins (both macromolecules/organic compounds) were the source of the genetic information

3. Griffith: 1st major experiment; studied the pneumonia bacteria in mice
concluded that there had been a “transformation” , but did not know what the transforming substance was

4. Avery:
identified the molecule that was “transformed” in Griffith’s experiment
concluded that DNA was released & caused the change
many did not believe him

5. Hershey & Chase:
provided definite evidence that DNA was the transforming factor
used a bacteriophage (virus that attacks bacteria)

6. Levene: determined the basic structure of nucleotides that make up DNA
proved nucleotides were made up of sugar, phosphate, and a nitrogenous (nitrogen) base

7. Chargaff: analyzed nitrogen bases found that the amount of
Adenine=Thymine
Cytosine=Guanine

8. Rosalind Franklin: collected data eventually used by Watson & Crick
took “Photo 51” (see pg. 330) through
x-ray diffraction

9. Watson & Crick:
used everyone else’s data to build the model of DNA = double helix
means “twisted ladder”
backbone is made up of sugars and phosphates
hydrogen bonds hold nitrogen bases together

10. DNA is in the form of a twisted ladder
DNA is in the form of a twisted ladder. What is the official name of this twisted ladder?
Double helix

11. 5-carbon sugar (deoxyribose)
In DNA, the “rungs” of the ladder are made up of nitrogen bases. What are the sides of the ladder made up of? (2 things)
5-carbon sugar (deoxyribose)
phosphate

12. Nitrogen bases always pair with the same thing
Nitrogen bases always pair with the same thing. List the 4 nitrogen bases, along with their pairs:
Adenine = Thymine
Guanine = Cytosine

13. What are the 3 parts of a nucleotide?
5-carbon sugar (deoxyribose)
Phosphate
Nitrogenous (nitrogen) base

14. Draw a sample below:

15. Important chromosome characteristics:
51 million – 245 million base pairs
DNA tightly coils around proteins called histones to fit within a cell
Nucleosome = negative charge from phosphate group + positive charge from histone proteins