Lesson 17: Molecular Base Of Inheritance Flashcards
What was a common view about hereditary information in the 1900s?
Proteins must carry the hereditary information, not much was known about nucleic acids, and with only four nucleotides in DNA, it seemed unlikely that DNA could account for the great variety of life
What do viruses do?
Force cells to make more viruses. Viruses are simple structures, they consist of DNA surrounded by a protein coat
What was the Hershey/Chase experiment (1952)?
Viral protein coat with radioactive sulfur (DNA does not contain sulfur) or DNA with radioactive phosphorus (very little phosphorus in protein). They found that DNA is the genetic material of viruses
What are Chargaffs rules?
Erwin Chargaff examined the percentage of each base of DNA (G,A,T, and C) in different species and found that it varied among species
What did chargaff find about the percentages?
Percentage of A and T is always equal and the percentage of G and C are always equal
What was the main takeaway of Chargaffs rules?
The base composition of DNA varies between species and within a species, the number of A and T bases are equal, and the number of G and C bases are equal
What did Watson and Crick do?
Elucidated the structure of DNA in 1953 and won a Nobel prize in 1962. They said the structure suggests a way for hereditary information to be passed on. In the early 1950’s the arrangement of covalent bonds in DNA was known, but not how strands of DNA interacted together
What did Rosalind Franklin do?
She was an X-ray crystallographer working at Cambridge on the structure of DNA. She produced the best image available of DNA. The image suggests that DNA consists of a double helix. James Watson and Francis Crick were given access to Franklins data
How did Watson and Crick use Franklins data?
Knew the structure of one strand of DNA. From Franklins data they knew that DNA adopted a double helical shape. Also learned from Franklin that the sugar and phosphates were on the outside of the helix. Watson and Crick worked out the hydrogen bonds between the bases and that the two strands were antiparallel
What are the DNA base pair rules?
A & T form 2 H bonds ( A-T-2, stick letter with stick letter)
C & G form 3 H bonds (C-G-3, curvy letters with curvy letters)
