DNA Experiments and structure

what were the 6 experiments that identified DNA as the genetic material and determined its structure?

Griffith, Avery, Hershey-Chase, Chargaff, Franklin & Wilkins, and Watson & Crick

What was Griffiths Experiment?

He used mice and pneumonia bacteria, strain S was harmful (pathogenic), and strain R was not harmful (non-pathogenic). The R strain (harmless) mixed with strain S (harmful) killed the mice. Some factor was transferred from the S to R bacteria turning the harmless R strain into something deatly.

What did Griffith Discover?

transformation-one bacteria was genetically changed by another bacteria

during the point of griffiths experiments what were scientists not sure about?

whether the transforming factor was DNA or Protein

why did avery extend griffiths experiment?

to figure out what the transforming factor was.

what happened during averys experiments?

used enzymes to digest various components of the bacteria: DNA, RNA, and Proteins. Transformation did not take place only when the DNA from the harmful bacteria was digested by the enzymes.

what did avery’s experiment discover?

that DNA stores and transmits genetic information

What did hershey and chase use for their exxperiment?

viruses that infect bacteria (bacteriophages), radioactive phosphorus to mark the DNA, and radioactive sulfur to mark the proteins.

what happened during Hershey and Chase’s experiment?

This allowed them to trace where these molecules went during the viral infection process. Demonstrated that DNA was the genetic material.

What did chargaff determine?

that the amount of adenine is the same as the amount of thymine in all the organisms he studied (and that C=G).

What did Franklin and Wilkins do?

they did x-ray crystallography pictures of the DNA molecule that showed it to be a helical structure with at least 2 helices.

Using Chargaffs rules what did watson and crick know?

A=T and C=G

Using the x-ray pictures from franklin and wilkins experiment what did watson and crick know?

it was a helical shape, they knew the structure had to provide a way to replicate very accurately

what did Watson and Crick determine?

the structure of DNA in 1953, the structure of DNA was a double helix with bases on the inside and sugar and phosphate alternating on the outside.

what are the DNA Basics?

Deoxyribonucleic acid, double helix, and located in the nucleus of eukaryotic cells. (prokaryotes lack a nucleus but still have DNA in their cells, while prokaryotic DNA hangs out in the nucleoid region.

How is DNA a nucleic acid?

its an organic compound made up of carbon, hydrogen, nitrogen, oxygen, and phosphorus, its also made of repeating subunits (monomers) called nucleotides.

what is a nucleotide made of?

a sugar, a phosphate group, and one of 4 nitrogen bases

what are the 2 categories of nitrogen bases?

Pyrimidines (1 ring), and Purines (2 rings)

what are the nitrogen bases in pyrimidines?

cytosine and thymine

what are the nitrogen bases in purines?

adenine and Guanine

what is the structure of DNA?

the sides of the ladder are the sugar and phosphate group, the rungs (part you step on) are 2 of the nitrogen bases, each rung is one purine paired with one pyrimidine always C-G and A-T.

what is DNA replication?

the process of making identical copies of DNA. It is semiconservative-in each molecule, there is one old and one new strand.

when does DNA replication occur

during the S phase of the cell cycle

what is DNA replication necessary?

for cell division

what is step 1 of DNA replication?

DNA helicase (an enzyme) unwinds the molecule

what is step 2 of DNA replication?

DNA polymerase binds free floating nucleotides to the exposed bases on the original strands.

what is step 3 of DNA replication?

the 2 molecules wind up again