1 / 14

Discoveries Surrounding the Chemical Nature of the Gene Part 2

Discoveries Surrounding the Chemical Nature of the Gene Part 2. DNA Carries Genes. So now we’re pretty sure that it is DNA that carries genetic information. But how does it do these things: Carry information from one generation to the next?

jatin
Download Presentation

Discoveries Surrounding the Chemical Nature of the Gene Part 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Discoveries Surrounding the Chemical Nature of the GenePart 2

  2. DNA Carries Genes • So now we’re pretty sure that it is DNA that carries genetic information. • But how does it do these things: • Carry information from one generation to the next? • Put that information to work and give organisms the traits they have inherited? • Copy itself so that all of the genetic information is passed on to each cell during cell division?

  3. Well let’s talk about DNA for a minute What do you already know about DNA?

  4. Structure of DNA • Carbon and Phosphate backbone • Nucleotides • There are 4 Nucleotides in DNA

  5. Nucleotides There are 4 nucleotides in DNA • Thymine, Adenine, Cytosine, Guanine • Purines have a 2 ring structure • Adenine and Guanine • Pyrimidines have a 1 ring structure • Thymine and Cytosine

  6. Nucleotides • In the late 1940’s and early 1950’s scientists thought of DNA as just a string of nucleotides. • These nucleotides can be hooked together in any number of combinations. • But so can other molecules. • So what makes DNA special?

  7. Erwin Chargaff 1950 • Discovered that in the percentages of guanine [G] and cytosine [C] are almost equal in any sample of DNA • The same thing is true for adenine [A] and thymine [T].

  8. Chargaff’s Rule • [G]=[C] and [A]=[T] • Does anybody have an explanation for this? • Chargaff and other scientists did not have an explanation. They didn’t know why this occurred.

  9. Rosalind Franklin 1952 • Studied DNA • Used a technique called X-ray diffraction to get information about the structure of DNA. • It’s arrangement. • She aimed an X-Ray beam at samples of DNA and recorded the scattering pattern of X-rays on film. • Like the patterns you get when you get your arm X0-rayed.

  10. Franklin

  11. Franklin • Does this really give you a lot of information about the structure of DNA? • But it did provide some important clues. • It suggests that there are two strands to the structure • And those strands are twisted around each other.

  12. James Watson and Francis Crick 1953 • Someone showed Watson a picture of Franklin’s X-Ray of DNA. • Together they puzzled out the shape of DNA • Their model of DNA was a DOUBLE HELIX. • Two strands of DNA wound around each other.

  13. DNA Double Helix

  14. So let’s Summarize • Who was Erwin Chargaff? • What was his rule? • What did Rosalind Franklin do with X-Rays? • What did her picture look like? • What did Watson and Crick figure out when they Saw Franklin’s Picture?

More Related