Genetics Chpt. 12 and 13 Flashcards
How many bands of DNA would be expected in
Meselson and Stahl’s experiment after two rounds
of conservative replication?
two
Replicons
units of replication
Conservative Replication
one is entirely new DNA, and the other is made of old DNA strands
Dispersive Replication
the original DNA double helix breaks apart into fragments, and each fragment then serves as a template for a new DNA fragment
Semi-Conservative Replication
every new DNA double helix would be a hybrid that consisted of one strand of old DNA bound to one strand of newly synthesized DNA
Theta
circular DNA, no break in nucleotide strand, 1 replicon, unidirectional/bidirectional
Rolling-Circle
circular DNA, break in nucleotide strand, 1 replicon, unidirectional
Linear Eukaryotic
linear DNA, no break in nucleotide strand, many replicons, bidirectional
Which type of replication requires a break in the
nucleotide strand to get started?
Rolling-Circle Replication
Requirements for DNA Replication
template strand, nucleotides, enzymes and other proteins
DNA replication takes place in a
semiconservative model
Replication runs from
5’ to 3’
Nucleotides get added to what end
3’
Leading Strand
undergoes continuous replication
Lagging Strand
undergoes discontinuous replication
Okazaki Fragments
discontinuously synthesized
short DNA fragments forming the lagging strand
Discontinuous replication is a result of which
property of DNA?
antiparallel nucleotide strands
Place the following components in the order in
which they are first used in the course of
replication:
helicase
single-strand-binding protein
DNA gyrase
initiator protein
initiator protein, helicase, single-strand-binding protein, DNA gyrase
Primers
an existing group of RNA nucleotides with a
3’-OH group to which a new nucleotide can be
added; they are usually 10–12 nucleotides long
Primase
RNA polymerase…synthesize primers with a 3’-OH group at the beginning of each DNA fragment
Primers are synthesized where on the lagging
strand?
at the beginning of every okazaki fragment
Helicase
unwinds the DNA
Single-Strand-Binding Proteins
protect the single nucleotide strands and prevent secondary structures
DNA Gyrase
remove strain ahead of the replication fork
DNA Polymerase I
removes and replaces primers
DNA Polymerase III
carries out elongation
Ligase
connects nicks (Okazaki fragments) after RNA primers are removed
Termination
when the replication fork meets or by a termination protein
DNA Polymerase II
DNA repair; restarts replication DNA; halts synthesis
DNA Polymerase IV
DNA repair
DNA Polymerase V
DNA repair; translesion DNA synthesis
Polymerase generally
synthesized the leading and lagging strands
Which bacterial enzyme removes the primers?
DNA polymerase I
Proofreading
DNA polymerase I: 3’ - 5’ exonuclease activity removes the incorrectly paired nucleotide
Mismatch Repair
corrects errors after replication is complete
Which mechanism requires the ability to
distinguish between newly synthesized and
template strands of DNA?
mismatch repair
In comparison with prokaryotes, what are some
differences in the genome structure of eukaryotic
cells that affect how replication takes place?
The size of eukaryotic genomes, the linear
structure of eukaryotic chromosomes, and the
association of DNA with histone proteins
Some of the eukaryotic DNA polymerases have a
tendency to make errors in replication.
Why would a cell use an error-prone DNA
polymerase instead of one that is more accurate?
Error-prone DNA polymerases can bypass lesions
in the DNA helix that stall accurate, high-speed
DNA polymerases
What would be the result if an organism’s
telomerase were mutated and nonfunctional?
Chromosomes would shorten each generation
Why is recombination important?
Recombination is important for genetic variation
and for some types of DNA repair.
What is the function of resolvase in recombination?
It cleaves the Holliday structure
Ribozymes
catalytic RNA
Ribosomal RNA (rRNA)
structural and functional components of
the ribosome
Messenger RNA (mRNA)
carries genetic code for proteins
Transfer RNA (tRNA)
helps incorporate amino acids into
polypeptide chain
Transcription requires
DNA template, raw materials (ribonucleotide triphosphates), transcription apparatus
Transcribed strand is
template strand
The transcription unit is composed of
a promoter, RNA-coding sequence, and terminator
What is the difference between the template strand
and the nontemplate strand?
The template strand is the DNA strand that is copied
into an RNA molecule, whereas the nontemplate strand
is not copied
Which of the following phrases does NOT describe
a function of the promoter?
signals where transcription ends
Sigma Factor
binding to the promoter when transcription starts
In transcription, nucleotides are added to the
3’ end
What is the function of the sigma factor?
The sigma factor controls the binding of RNA
polymerase to the promoter
What binds to the −10 consensus sequence found
in most bacterial promoters?
holoenzyme (core enzyme + sigma factor)
What characteristics are most commonly found in
rho-independent terminators?
inverted repeats followed by a string of adenine
nucleotides
The promoters of genes transcribed by RNA
polymerase II consists of two primary parts
a core promoter and a regulatory promoter
What is the difference between the core promoter
and the regulatory promoter?
Both b and c above
What is the role of TFIID in transcription initiation?
RNA polymerase over the transcription start site
How are the processes of RNA polymerase II
termination in eukaryotes and rho-dependent
termination in bacteria similar, and how are
they different?
Both processes use a protein that binds to the RNA
molecule and moves down the RNA toward the RNA
polymerase.
They differ in that rho does not degrade the RNA,
whereas Rat1 does.
