Chapter 12-1:DNA: The Genetic Material Section objectives: –Describe the experiments that showed that DNA is the genetic material. –List the three chemical parts of a DNA molecule. –Explain the Watson-Crick model of DNA. –Describe how DNA replicates in a living cell.

History (tab 2) 1869: Friedrch Miescher isolated material from nucleus of fish sperm. Called material nuclein.

History 1920’s, scientists found that chromosomes contained DNA. While chemical structure of proteins was well understood, DNA was not. –Many believed proteins carried genetic info. 12-1

History 1928: Frederick Griffith found that some factor from harmful, but dead bacteria could transform harmless bacteria into deadly bacteria. 12-1

12-1

12-1

History Many still thought protein carried hereditary info. Then came Alfred Hershey and Martha Chase in

Their exp’t conclusively showed DNA to be the genetic material (not proteins) 12-1

The problem then became that of finding what DNA is made of and how it works! 12-1

Composition of DNA (tab 3) 5-carbon sugar: deoxyribose5-carbon sugar: deoxyribose A phosphate groupA phosphate group 4 kinds of nitrogen-containing bases4 kinds of nitrogen-containing bases –Adenine –Guanine –Cytosine –Thymine purines pyrimidines 12-1

Put these together and you have a nucleotide: 12-1

Structure of DNA James Watson (American biochemist)James Watson (American biochemist) Francis Crick (English physicist)Francis Crick (English physicist) Used X-ray photos from Rosalind Franklin.Used X-ray photos from Rosalind Franklin. 12-1

12-1

(1920 – 1958) 12-1

Shoe Fitting X- Ray Device 12-1

By 1970 had been banned in 33 states 12-1

DNA Double Helix

12-1

Remember! A pairs with TA pairs with T G pairs with CG pairs with C A-T, G-C 12-1 A and T are made from sticks: G and C are made from curls:

12-1

Avery and other scientists discovered that DNA is found in a protein coat. DNA stores and transmits genetic information from one generation to the next. transformation does not affect bacteria. proteins transmit genetic information from one generation to the next.

The Hershey-Chase experiment was based on the fact that DNA has both sulfur and phosphorus in its structure. protein has both sulfur and phosphorus in its structure. both DNA and protein have no phosphorus or sulfur in their structure. DNA has only phosphorus, while protein has only sulfur in its structure.

DNA is a long molecule made of monomers called nucleotides. purines. pyrimidines. sugars.

Chargaff's rules state that the number of guanine nucleotides must equal the number of cytosine nucleotides. adenine nucleotides. thymine nucleotides. thymine plus adenine nucleotides.

In DNA, the following base pairs occur: A with C, and G with T. A with T, and C with G. A with G, and C with T. A with T, and C with T.

Quiz (you may use notes) 1.What 3 subunits comprise a nucleotide? 2. Whose work with viruses and bacteria showed that DNA was the genetic material? 3.What 3 scientists discovered the structure of DNA? 4.What 4 nitrogenous bases make up the rungs of the DNA ladder? (you can abbreviate)

All About Bibliography History/Famous People DNA Structure RNA How it all works!