Ch. 15 DNA - The Genetic Material! Flashcards
Explain the procedure for the Hershey-Chase Experiment
Used simple model organism and experiment set up (Bacteriophage)
Bacteriophage has a protein coat and a DNA core on the “head” and wanted to figure out which part is being injected into the bacteria( E.coli cells)
Used radioactive sulfur(isotope) for the protein; Only found in proteins, not DNA
Used radioactive phosphate(isotope) for DNA; Clever, since phosphate only found in DNA
Wanted to take things above things and note if radioactive signals were outside or inside bacteria; Separated bacteria and bacteriophages from outside using type of blender(Centrifugation)
Bacteria bigger, so should end up on bottom while virus on top of tube in separation
Bacteriophage
virus that infects bacteria
* Attaches outside of bacteria
* Injects substance into bacteria to create multiplication of the virus
* So substance should hold hereditary material, but what is that considered?
What was the end goal for the Hershey-Chase Experiment?
Wanted to know if DNA or protein was the hereditary material!
Results of Hershey-Chase Experiment
Radioactive sulfur on the virus showed the proteins stayed with the main virus and were not found in viruses injected into the bacteria
This means the proteins are not being inherited
Radioactive phosphate showed traces of the DNA from the virus in the injected viruses in the bacteria
Means DNA was being inherited
o DNA is the hereditary material!!!
Has some function in bacteria multiplication, while protein does not
Who discovered the helical shape of DNA?
Rosalind Franklin, used x-ray diffraction
Who discoverd complimentary base-pairing?
Watson and Crick
A/T and G/C form hydrogen bonds
Runs antiparrallel
Double helix structure
What does it mean for replication to be semiconservative?
THE CORRECT MEANS FOR WHICH REPLICATION OCCURS!!!
mechanism by which DNA is replicated, meaning that each newly synthesized DNA molecule consists of one original (or parental) strand and one newly synthesized (or daughter) strand
Each strand serves as a template for the synthesis of a new complementary strand by the enzyme DNA polymerase
Semiconservative replication is important because it ensures that the genetic information in the original DNA molecule is accurately passed on to the new daughter cells during cell division. Without this process, errors in DNA replication could lead to mutations and genetic diseases.
What does it mean for replication to be conservative?
HYPOTHESIS OF DNA REPLICATION PROVEN FALSE
hypothetical model for DNA replication that suggests that the original double-stranded DNA molecule remains intact and serves as a template for the synthesis of a completely new double-stranded DNA molecule. In this model, no mixing of the parental and newly synthesized DNA strands occurs
What does it mean for replication to be disperse?
HYPOTHESIS OF DNA PROVEN FALSE
creates all four strand to be of intermediate density
How was disperse and conservative replication proven wrong?
Meselson-Stahl experiment in 1958, which supported the alternative model of semiconservative replication. In this model, the two strands of the parental DNA molecule separate and each strand serves as a template for the synthesis of a new complementary strand, leading to two daughter DNA molecules, each consisting of one parental strand and one newly synthesized strand.
How does DNA replication work?
DNA is its own template!!
Synthesis reaction
Enzyme called DNA polymerase “reads” one strand in the 3’ to 5’ direction, but “writes” a new strand in the 5’ to 3’ direction
Other enzymes and proteins open/unwind/stabilize helix
