DNA Flashcards
How did Hershey and Chase come up with their theory?
They used radioactive labelling and a centrifuge.
Hershey & Chase
DNA, not protein is the genetic material that a virus infects a bacteria with. DNA is the hereditary material of bacteriophage viruses (blender).
Chargaff: “Chargaff’s rules”
In DNA, the amount of guanine(G) should be equal to the amount of cytosine(C) and the amount of adenine(A) should be equal to the amount of thymine(T). There is a 1:1 ratio of pyrimidine and purine bases
How did Chargaff come up with his theory?
Analyzed the base composition of DNA from various organisms
Watson-Crick-Wilkins-Franklin (& Pauling)
DNA structure: the double-helix structure of DNA
How did Watson-Crick-Wilkins-Franklin (& Pauling) come up with their theory?
Used X-ray diffraction data from Rosalind Franklin and Maurice Wilkins. Constructed a model of DNA as a double helix.
What are the components of a nucleotide?
A nitrogenous base, a sugar(deoxyribose for DNA, ribose for RNA), and a phosphate group
What types of bonds hold nucleotides together?
hydrogen bonds
What are the base pairing rules in DNA?
Adenine to Thymine (Apples to Trees)
Guanine to Cytosine (Car to Garage)
Differences between DNA & RNA?
DNA is double-stranded, RNA is single-stranded.
DNA contains the sugar deoxyribose, RNA contains the sugar ribose.
DNA uses the base thymine, and RNA uses uracil in its base pair.
What are 5’ and 3’ ends? (where do these terms come from?)
the two ends of a nucleic acid strand, like DNA or RNA and they are named after the carbon number on the sugar molecule that is free at that end
Why is DNA referred to as antiparallel?
the two strands that make up the double helix run in opposite directions to each other. One strand goes from 5’ to 3’ while the other goes from 3’ to 5’
What does it mean to call the DNA strands complementary?
the two strands of the double helix have a specific base pairing relationship (A-T)(G-C)
DNA replication takes place where in a Eukaryotic cell? Prokaryotic cell?
Eukaryotic: nucleus
Prokaryotic: cytoplasm
Why is DNA replication called semi-conservative?
When replicating, it uses one old strand of DNA and creates a new strand
What is a replication bubble?
Replication bubble: the region of DNA where the double helix is unwound, creating an open area where DNA replication can occur
What is the origin of replication
a specific nucleotide sequence on the DNA where the initial unwinding occurs, marking the starting point for DNA replication.
What is a replication fork?
At each end of the replication bubble, where the DNA strands are actively being separated and copied, there is a Y-shaped structure called the replication fork
new strand only grows 5’ –> 3’
the enzyme responsible for building the strand, DNA polymerase, can only add nucleotides to the 3’ end of an existing strand
differences between leading & lagging strands
lagging strand: replicates discontinuously, form short fragments
leading strand: replicates continuously
What are Okazaki fragments? Why are these created?
Small sections of DNA that are formed during discontinuous synthesis of the lagging strand during DNA replication
What are RNA primers? What enzyme creates these?
RNA primers are short sequences of RNA nucleotides that act as a starting point for DNA synthesis. They are created by an enzyme called primase
Helicase
“Unzips” the DNA
Primase
synthesizes short RNA primers on the DNA strands
