DNA structure and function PT 2 Flashcards
Replication of DNA takes place during _______, before/after nuclear division.
Replication of DNA takes place during interphase, before nuclear division.
What are the enzymes involved in DNA replication?
Helicase, Primase, DNA Polymerase III + DNA Polymerase I, DNA Ligase
What is the role of helicase in DNA replication?
Helicase unwinds the double helix by breaking the hydrogen bonds between the complementary base pairs in the parental strand.
Each parental strand acts as the ______ for the synthesis of a new DNA strand.
Each parental strand acts as the template for the synthesis of a new DNA strand.
What is the role of primase?
Primase attaches to the unwound chain and catalyses the synthesis of RNA primer to provide free 3’ OH ends for DNA polymerase III.
What is the role of DNA Polymerase III?
DNA Polymerase III elongates the new daughter strand in the 5’ to 3’ direction by catalysing phosphodiester bond formation between the incoming deoxyribonucleotides and the free 3’ OH end of the daughter strand.
The ______ strand is synthesised continuously while the ______ strand is synthesised discontinuously to form Okazaki fragments.
The leading strand is synthesised continuously while the lagging strand is synthesised discontinuously to form Okazaki fragments.
RNA primers are removed and replaced by deoxyribonucleotides by ______ (enzyme).
RNA primers are removed and replaced by deoxyribonucleotides by DNA polymerase I.
____ between the Okazaki fragments are filled in by _______ (enzyme) by forming phosphodiester bonds between fragments.
Nicks between the Okazaki fragments are filled in by DNA ligase by forming phosphodiester bonds between fragments.
Using results from generation 1 from the Messelson-Stahl experiment, describe and explain how the model semiconservative DNA replication is supported.
Both the original/parental strands contain only 15N. Each 15N strand served as a template for replicating a new/daughter 14N strand.
If replication is semiconservative, in the first generation, the isolated DNA showed only one single band of intermediate density.
Where each replicated hybrid DNA molecule was composed of one new/daughter 14N strand and one parental 15N strand.
Electrophoresis is a technique used to separate DNA, RNA and proteins that differ in ____, ______, or _______.
Electrophoresis is a technique used to separate DNA, RNA and proteins that differ in size, charge, or conformation.
Nucleic acids have a consistent ______ charge imparted by their _______ _______ and migrate toward the ______.
Nucleic acids have a consistent negative charge imparted by their phosphate backbone and migrate toward the anode.
Fragments of linear DNA with _____ molecular weight will migrate through agarose gels slower and hence travel a shorter/further distance than those with a _____ molecular weight.
Fragments of linear DNA with heavier molecular weight will migrate through agarose gels slower and hence travel a shorter/further distance than those with a lighter molecular weight.
What are the 2 functions of loading dye?
- to colour the DNA
- to increase the density of DNA so that it is denser than the running buffer so that DNA samples will sink into the well
What is the function of a DNA ladder?
It is to quantify DNA molecules in terms of their size. By using appropriate molecular weight standards, the size (in basepairs, bp) of the unknown DNA bands can be determined.
