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37 Cards in this Set

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in DNA replication, nucleotides are added to which end of the DNA molecule?
3' end
the addition of a nucleotide to a growing DNA molecule is made energetically favorable how?
hydrolysis of pyrophosphate
what is meant by semi-conservative DNA replication?
resulting DNA has one parent strand and one daughter strand
DNA polymerases require which 3 things?
nucleotides, template, primer
how many origins of replication are present in bacterial DNA replication? Human DNA replication?
one; many
what are the names of the 3 phosphates, in order of proximity to ribose sugar?
alpha, beta, gamma
what is the destiny of the pyrophosphate molecule? This is catalyzed by which enzyme?
broken down into 2 inorganic phosphate molecules; pyrophosphatase
DNA replication begins with the binding of which protein to the origin of replication to unwind DNA? Does this process require energy?
DnaA; yes, ATP
what happens following DnaA binding and unwinding at origin of replication? Is energy used in this process?
helicase binds to unwound DNA at origin and separates DNA strands; yes, ATP
which proteins are responsible for keeping separated DNA strands apart?
single-stranded binding proteins (SSB)
which protein is responsible for creating a RNA primer for the start of DNA replication? In what class is this protein?
primase; RNA polymerases
other than the obvious, what is a large difference between RNA and DNA polymerases?
RNA polymerase can create a polynucleotide de novo
what is meant to say DNA polymerases are processive?
they carry out multiple rounds of nucleotide addidion and do not fall off template until they reach the end or are actively unloaded.
processivity of DNA polymerase is conferred by which subunit?
what is the name for the fragments which compose the lagging strand in DNA replication?
Okasaski fragments
is DNA polymerase which synthesizes lagging strand always bound?
no, it binds once DNA is sufficiently unwound for the formation of a new fragment.
which DNA polymerase is responsible for enlongating DNA from RNA primer?
DNA polymerase III
which DNA polymerase is responsible for removing the RNA primer at the beginning of each Okasaki fragment?
DNA polymerase I
which DNA polymerase is responsible for replacing RNA primer with DNA?
DNA polymerase I
which DNA polymerase, I or III, is faster at enlongating polynucleotide chain?
DNA polmerase III
which enzyme is responsible for sealing the nick remaining between two Okasaki fragments?
DNA ligase
which property of DNA ligase prevents it from ligating Okasaki fragments prematurely (before RNA is removed)?
it can only ligate together two DNA molecules
what is the function of topoisomerase? How is this done?
to release tension on DNA molecule as it becomes unwound; by nicking one strand of DNA, passing the other strang through the nick, and resealing the nick.
most errors in DNA replication are due to what?
the fact that a base was incorporated while in its tautomeric configuration
1 out of every how many bases laid by DNA polymerase is incorrect?
which DNA polymerase is capable of 3' to 5' exonuclease activity?
both I and III
what is the name for the ends of chromosomes?
what is the function of telomeres?
to protect the ends of chromosomes
what is the name of the enzyme responsible for adding telomeres?
telomerase elongates which strand of DNA from its 3' end?
lagging strand
which kind of nucleotides are added by telomerase?
during which phase of life, embryonic or adult, are telomeres longer? Why?
embryonic; most adult somatic cells lack telomerase activity.
what happens as telomeres shorten?
chromosomes tend to become fused together via their ends, leading to a higher rate of chromosome loss
what effect does overexpression of telomerase in cancer cells have?
it renders the cancer cells immortal
what is the name of the disease associated with a shortage of telomerase activity?
Dyskeratosis congenita
what is the name for the family of enzymes that can make DNA from an RNA template?
Reverse transcriptases
why are reverse transcriptases highly error prone?
they lack 3' to 5' exonuclease activity