bio 12

why is DNA like a book

"Like DNA, a book stores information. A book can also be copied and passed along to the next generation. Similarly, storing, copying, and transmitting information are the three main functions of DNA."

What happens if a part of DNA is missing?

"The loss of any DNA during meiosis might mean a loss of valuable genetic information from one generation to the next.

What is Waston and crick discover?

"breakthrough model of DNA was a double helix, in which two strands of nucleotide sequences were wound around each other.

What is Charagaff's Rule

"discovered that the percentages of adenine [A] and thymine [T] bases are almost equal in any sample of DNA. The same thing is true for the other two nucleotides, guanine [G] and cytosine [C]. The observation that [A] = [T] and [G] = [C].

GRIFFITH'S EXPERIMENT: What are the 4 trails that he did?

Disease-causing bacteria (S) strain, Harmless bacteria (R) strain, Heat- killed bacteria (S) strain, Mixture of heat-killed (S) strain and live (R) strain---Live, disease-causing bacteria (S) strain.

HERSHEY & CHASE EXPERIMENT: What are the parts of the virus?

Head, DNA, Tail sheath and Tail fiber

HERSHEY & CHASE EXPERIMENT: The Experiment in detail?

Hershey and Chase needed to be able to examine different parts of the phages they were studying separately, so they needed to isolate the phage subsections. Viruses were known to be composed of a protein shell and DNA, so they chose to uniquely label each with a different elemental isotope. This allowed each to be observed and analyzed separately. Since phosphorus is contained in DNA but not amino acids, radioactive phosphorus-32 was used to label the DNA contained in the T2 phage. Radioactive sulfur-35 was used to label the protein sections of the T2 phage, because sulfur is contained in amino acids but not DNA.[1] Hershey and Chase inserted the radioactive elements into the bacteriophages by adding the isotopes to separate media within which bacteria were allowed to grow for 4 hours before bacteriophage introduction. When the bacteriophages infected the bacteria, the progeny contained the radioactive isotopes in their structures. This procedure was performed once for the sulfur-labeled phages and once for phosphorus-labeled phages.[1] The labeled progeny were then allowed to infect unlabeled bacteria. The phage coats remained on the outside of the bacteria, while genetic material entered. Centrifugation allowed for the separation of the phage coats from the bacteria. These bacteria were lysed to release phage progeny. The progeny of the phages that were originally labeled with 32P remained labeled, while the progeny of the phages originally labeled with 35S were unlabeled. Thus, the Hershey-Chase experiment helped confirm that DNA, not protein, is the genetic material. Hershey and Chase showed that the introduction of deoxyribonuclease (referred to as DNase), an enzyme that breaks down DNA, into a solution containing the labeled bacteriophages did not introduce any 32P into the solution. This demonstrated that the phage is resistant to the enzyme while intact. Additionally, they were able to plasmolyze the bacteriophages so that they went into osmotic shock, which effectively created a solution containing most of the 32P and a heavier solution containing structures called "ghosts" that contained the 35S and the protein coat of the virus. It was found that these "ghosts" could adsorb to bacteria that were susceptible to T2, although they contained no DNA and were simply the remains of the original bacterial capsule. They concluded that the protein protected the RNA from RNAse, but that once the two were separated and the phage was inactivated, the DNAse could hydrolyze the phage DNA.[1] Experiment and conclusions[edit] Hershey and Chase were also able to prove that the DNA from the phage is inserted into the bacteria shortly after the virus attaches to its host. Using a high speed blender they were able to force the bacteriophages from the bacterial cells after adsorption. The lack of 32P labeled DNA remaining in the solution after the bacteriophages had been allowed to adsorb to the bacteria showed that the phage DNA was transferred into the bacterial cell. The presence of almost all the radioactive 35S in the solution showed that the protein coat that protects the DNA before adsorption stayed outside the cell.[1] Hershey and Chase concluded that DNA, not protein, was the genetic material. They determined that a protective protein coat was formed around the bacteriophage, but that the internal DNA is what conferred its ability to produce progeny inside a bacteria. They showed that, in growth, protein has no function, while DNA has some function. They determined this from the amount of radioactive material remaining outside of the cell. Only 20% of the 32P remained outside the cell, demonstrating that it was incorporated with DNA in the cell's genetic material. All of the 35S in the protein coats remained outside the cell, showing it was not incorporated into the cell, and that protein is not the genetic material.[1] Hershey and Chase's experiment concluded that little sulfur containing material entered the bacterial cell. However no specific conclusions can be made regarding whether material that is sulfur-free enters the bacterial cell after phage adsorption. Further research was necessary to conclude that it was solely bacteriophages' DNA that entered the cell and not a combination of protein and DNA where the protein did not contain any sulfur.

What is Franklins's Rule?

It depicts an X-ray diffraction of DNA. Taken in 1951, the image eventually led to the conclusion that DNA was composed of a double helix. Such a structure consists of two helices (corkscrew structures) running in parallel.

GRIFFITH'S EXPERIMENT: What transferred?

Some of the heat-killed (S) strain into the live (R) strain

HERSHEY & CHASE EXPERIMENT: What type of virus were used?

T4 Bacteriophage

AVERY'S EXPERIMENT: What did he concluded?

That DNA was the transforming factor

AVERY'S EXPERIMENT: What where the end results?

That the enzymes they used did not make transformation occur

GRIFFITH'S EXPERIMENT: Which strain killed?

The (S) strain killed and the Mixture of the live (R) strain and the (S) strain

GRIFFITH'S EXPERIMENT: What is the S-strain?

The disease-causing bacteria. It grew into smooth colonies on culture plates.

GRIFFITH'S EXPERIMENT: What is the R strain?

The harmless bacteria. Produced colonies with rough edges.

HERSHEY & CHASE EXPERIMENT: The End result?

They repeated the experiment and found the radioactivity in the sediment with the bacteria, proving, that the DNA had indeed entered the bacteria. If the DNA wouldn't be the carrier, it wouldn't have entered the bacteria and would have stayed in solution.

HERSHEY & CHASE EXPERIMENT: What does the virus do?

its the bacteria eater

AVERY'S EXPERIMENT: What was his experiment?

to determine which molecule in the heat-killed bacteria was most important for transformation