CH 33-35 Flashcards
WHAT IS THE BACKBONE OF THE NUCLEIC ACID?
3’-hydroxyl group of the sugar is
bonded to a phosphoryl group, which is, in turn,
joined to the 5’-hydroxyl group of the adjacent sugar
in a phosphodiester linkage
Sugars in nucleic acids are linked by ___
Sugars in nucleic acids are linked by phosphodiester
bridges
DNA
deoxy” prefix
refers to the fact that the 2’-carbon atom of the sugar lacks the oxygen atom
Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
RNA
Adenine (A), Uracil (U), Cytosine (C), Guanine (G)
NUCLEOSIDE
A unit consisting of a base bonded to a sugar
NUCLEOTIDE
a nucleoside joined to one or more phosphoryl groups by an ester linkage
NUCLEOSIDE TRIPHOSPHATES
are the monomers—the building blocks—that are linked to form RNA and DNA, and pyrophosphate is
released when the nucleotides are linked
The double helix is stabilized by ____ and the ____
The double helix is stabilized by hydrogen bonds and the hydrophobic effect
○
HYDROPHOBIC EFFECT
hydrophobic interactions between the bases drive the bases to the interior of
the helix, resulting in the exposure of the more polar surfaces to the
surrounding water
○ stacked bases attract one another through van der Waals forces - a
phenomenon called base stacking
NUCLEOSOMES
complexes of DNA and Histones
Repeating units of chromatin
CHROMATIN
The entire complex of a cell’s DNA and associated protein is called chromatin
Five major histones are present in chromatin: four histones, called H2A, H2B, H3, and H4, associate with one another;
the other histone is called H1
repeating units containing 200 dp of DNA and two copies of each histones (histone octamer)
Eukaryotic DNA is wrapped around ____ to form ____
Eukaryotic DNA is wrapped around histones to form nucleosomes
____ catalyzes phosphodiester-linkage
formation
DNA polymerase catalyzes phosphodiester-linkage
formation
PHOSPHODIESTER LINKAGE FORMATION
Requires all four activated precursors and Mg2+ ions
New DNA is assembled directly on to preexisting DNA
Requires a primer
5’»>3’
____ catalyzes phosphodiester-linkage
formation
DNA polymerase catalyzes phosphodiester-linkage
formation
Most naturally occurring DNA molecules are
Most naturally occurring DNA molecules are negatively supercoiled
Topoisomerases can relieve negative supercoil tension through
Topoisomerases can relieve negative supercoil tension through temporary cleavage of DNA or introduce negative
supercoils into DNA
PROOFREADING OCCURS AT WHICH END OF THE GROWING CHAIN
3’
Arrange the steps of DNA replication in the order that they occur.
FIRST STEP
helicase unwinds the DNA double helix
single DNA binding proteins bind to each template strand
RNA primers are added
DNA polymerase synthesizes DNA
RNA primers are removed
DNA ligase joins DNA fragments together
DNA replication involves multiple steps that require different enzymes. Which process does primase catalyze in DNA replication?
synthesis of a short RNA sequence that initiates DNA synthesis
DNA partially unwinds as the hydrogen bonds between complementary bases are broken.
This process is catalyzed by the enzyme
helicase
The Okazaki fragments are joined together by the enzyme
DNA ligase
As DNA is replicated, both continuous and discontinuous replication occur. Discontinuous replication is the result of which specific feature of DNA?
antiparallel strands
