Chapter 12: Molecular Genetics

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

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

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

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

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

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

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

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

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

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

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

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

Draw a sample below:

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