2.7 Flashcards
Roslin Franklin’s Xray diffraction model suggested what key points about the three-dimensional
structure of DNA?
Is DNA a left-handed or right-handed helix?
What does it mean that the two strands of DNA are anti-parallel?
What is the “backbone” that each strand of DNA made up of and what is in the middle?
Describe the bonds that hold the nucleotides of the same strand together and contrast these with the
bonds that hold the two strands together:
How does a 5’ end differ from a 3’ end?
WHat is the starting place of replication called in prokaryotes?
What shape is the DNA in prokaryotes?
How many initiation points are there?
Does replication proceed in only one direction or in both directions from the origin?
Where does replication begin in eukaryotes?
What shape is the DNA in eukaryotes?
How many initiation points are there in eukaryotes?
Does replication proceed in only one direction or in both directions from the origin?
What is a replication fork?
Helicase
Single stranded binding proteins (SSBPs)
Topoisomerase
Primase
The enzymes that replicate DNA cannot initiate a polynucleotide, they can only add to an existing
chain. This chain is not actually DNA, it is _______________ and called primer (5-10 nucleotides).
The next nucleotide is always added to the _______________end of the primer and growing
polynucleotide chain.
Building a DNA molecule requires energy. This energy is part of a set of reactions related to the last
two _________________ that are lost from each nucleotide before being incorporated
Why are there “leading strands” and “lagging strands” during replication
Does each Okazaki fragment have its own RNA primer?
DNA pol I
DNA ligase
DNA sequencing
DNA polymerase makes mistakes during replication. When it does happen, can mistakes be
repaired? If so, how?
double helix
the form of native DNA, referring ot its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape
antiparallel
referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run in opposite 5’ to 3’ directions)
semiconservative model
type of DNA replication in which the replicated double helix consists of one old strand, derived form the parental molecule, and one newly made strand
replication fork
a y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized
helicases
an enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands
single-strand binding proteins
a protein that binds to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA
topoisomerase
an enzyme that helps relieve strand of untwistng the double helix by breaking, swiveling, and rejoining DNA strands
primer
short polynucleotide with a free 3’ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication
primase
an enzyme that joins RNA nucleotides to make a primer during DNA replication, using the parental DNA strand as a template
DNA polymerase
an enzyme that catalyzes he elongation of new DNA by the addition of nucleotides to the 3’ end of an existing chain
leading strand
the new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5’ to 3’ direction
lagging strand
a discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5’ to 3’ direction away from the replication fork
okazaki fragments
a short segment of DNA synthesized away from the replication fork on a template strand during DNA replication. Many such segments are joined together to make up the lagging strand of newly synthesized DNA
DNA ligase
a linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3’ end of one DNA fragment tot eh 5’ end of another DNA fragment
DNA sequencing
determining the order of nucleotide bases in a gene of DNA fragment