chapter 7: Dna Flashcards
what is the R type of bacteria in the Griffiths experiment?
rough bacteria which has no polysaccharide Capsule so it is antivirulent
how did Griffith discover transformation?
S. bacteria has a poly saccharide capsule and are pathogenic. When they are injected into mice, The mice die. R. bacteria don’t have the capsule and don’t kill mice. Heat – killed bacteria are dead but still have the capsule. They don’t kill mice but if heat killedbacteria are injected with live R. bacteria then the mice die. The S. strain is transforming The R. strain into virulent disease.
what did the Avery team do? And how?
The Avery team discovered that the transforming principal resemble DNA in several ways
-same chemistry and behavior as DNA
– Not affected by lipid and protein expection
– Not destroyed by protein or RNA – digesting enzymes
– Was destroyed by DNA – digesting enzymes
based on this overwhelming evidence, but Avery team concluded that the hereditary material was DNA
concepts of the Hershey and Chase experiment-what is a bacteriophage?
A bacteriophage is a virus that kills bacteria. Hershey and Chase use radioactive isotopes to label or tag the DNA and the protein of the viruses; some viruses were ground so that their DNA contains a radioactive phosphorus (32 P); other viruses we’re grown so that their protein coats contained radioactive sulfur (35 S). The bacterial phages infect bacterial cells and the bacterial cells are agitated to remove protein coat. The protein coat with the sulfur isotope were left outside and were fluorescent. The DNA with the radioactive phosphorus was left inside the bacteria and were fluorescent.The conclusion was that the teens that viruses used to specify new viruses are made of DNA and not protein.
what is chargaff’s rule?
Edwin Chartoff noted that DNA molecules always had equal amounts of purines and pyrimidines; Chargaff’s rule suggested that DNA had a regular structure
– The amount of a always equal the amount of t
– The amount of C always equal amount of g
because DNA is double helical
what are purines versus pyrimidines?
nucleotides differ with regards to their bases: large bases (purines) with double– ring structure either Adenine or guanine, Small bases (pyrimidines) with single rings either cytosine or thymine; purines combine with pyrimidines
DNA molecule is a double helix. How many bonds between a and T? And G and C?
thymine and adenine have two hydrogen bonds between each other and guanine and cytosine have three hydrogen bonds
suggested models of DNA replication
conservative, semi conservative, dispersive: semi conservative is The right way
concepts of the meselson and stahl experiment. Why did they use radioactive nitrogen?
combined E. coli DNA with 15 nitrogen Which is a heavy isotope and 14 nitrogen which is a light isotope. they used nitrogen because DNA has nitrogen.included cesium chloride as a gradient, which serves as a sieve or separator. Made 14 generations of E. coli so they did this for 14 nights. The strands of DNA were found in the middle, which means that they are semi conservative.
what is Helicase, gyrase, primase, DNA polymerase, Ligase?
Helicase: unwind the DNA to expose the templates; this creates a replication fork
gyrase: keeps the parent stands from coming back together
primase: Synthesizes a primer
DNA polymerase: adds the correct complementary nucleotides the growing got a strand, but can only add nucleotides to the 3 prime end of an existing stand or primer
DNA ligase: seals fragments of DNA together
five prime to three prime strand versus three prime to 5 prime strand
DNA has a deoxyribose sugar which is a five carbon ring. The fifth carbon is the five prime and the third carbon is the 3 prime. One strand of DNA goes from three prime to five prime and the other strand of DNA goes from five prime to three prime. DNA polymerase can’t synthesized DNA in the five prime end.
what is a leading strand versus a lagging strand?
at the replication forks, primer must first be added to give a place for DNA polymerase to start. using one template, DNA polymerase adds nucleotides in the continuous fashion; this new daughter strand is called the leading strand. Because the other template is A mirror image,directionality becomes a problem because DNA polymerase can build a new strand in One Direction only. this second daughter strand is assembled in segments, each one beginning with the primer. The segments are joined together by DNA ligase a form the lagging strand.
what are Okasaki fragments?
Okasaki fragments are short, newly synthesized fragments that are formed on the lagging template strand during DNA replication. They’re complementary to the lagging template strand, together forming short double – stranded DNA sections.
DNA replication system can make mistakes leaving and sudden changes in the genotype
this is called mutation
Griffith experiment – what is the S type bacteria
S bacteria equals smooth bacteria = polysaccharide capsule which causes disease A.k.a. virulent
