chapter 15 Flashcards
What is the advantage of multiple origins or replication (DNA)? disadvantage?
What domain of organism uses multiple origins of replication?
allows faster replication, repair and making new things. can make mistakes
archaea
if a cell lost the ability to provide single- stranded binding proteins, how would that mess with the process of DNA
The DNA would snap back close because the the hydrogen bonds, so no replication
if a cell lost the ability to produce ligase, how would that mess with DNA replication?
The nitrogenous bases would be missing phosphodiester bonds and there would just be fragments of DNA
explain why the ends of every DNA molecule become shorter with every replication. How is this problem solved temporarily
solve it by using telomers which are made of unused dna
which kinds of cells have a way to rebuild lost ends? What is the enzyme called
gametes
telomerase
using the idea of how a virus works, explain how we know DNA is a hereditary molecule.
because the viruses can incorporate their DNA into your DNA
Why is there always a leading and a lagging strand while replicating DNA
has to synthesize from 3’ to 5’, away from replication fork
why is DNA semiconservative
suggests that, after DNA replication,
the new DNA duplex consists of one old strand (parental) and one
new strand (daughter).
where does dna replication begin and what does this cause
begins at special sites called origins of replication where the 2 DNA strands are separated, opening up a replication bubble
what is DNA helicase
enzymes that separate the two strand of the double helix at the replication forks
what is single-strand DNA binding protein
bind to and stabilize single stranded DNA until it can be used as a template
topoisomerase who is this bitch
corrects “overwinding” ahead of the replication forks by breaking, swiveling and rejoining DNA strands
describe DNA polymerases
enzymes called DNA polymerases catalyze the elongation of a new DNA at the replication fork
what does DNA polymerase need
needs a primer and DNA template strand
can DNA polymerase initiate the synthesis of a polynucleotide
no, it cannot initiate the synthesis of a polynucleotide they can only add nucleotides to the 3’ end of a polynucleotide
what is the initial nucleotide stand?
is a short RNA primer The RNA primer is short and the 3’ end serves as the starting point for the new DNA strand.
what does primase do
can start an RNA chain from scratch and adds RNA nucleotides one at a time using the parental DNA as a template
what are the 3 components of a nucleotide
nitrogenous base, pentose sugar and phosphate group
how are nucleotides added to growing DNA stands
Each nucleotide that is added to a
growing DNA strand starts as a
nucleoside triphosphate.
o e.g., dATP supplies
__adenine__ to DNA.
What is the difference between ATP and dATP?
d says instead of ribose using deoxyribose
name 3 other nucleoside triphosphates that are used to synthesize DNA
dGTO,dCTP, dTTP
how is DNA built vs how is it read
build 5 to 3 but read 5’ to 3’
what happens when a monomer of dATP joins the DNA strand?
the monomer loses two phosphate groups as a molecule of pyrophosphate
- subsequent hydrolysis of pyrophosphate is coupled with exergonic reactions that help drive the polymerization reaction.
which way does DNA grow
DNA polymerase add nucleotides only to the 3’ end of a growing strand; therefore a new DNA strand can elongate only in the 5’ to 3’ direftion
leading vs lagging stand
leading strand moves continuously towards the replication fork.
DNA polymerase III must work away from the replication fork.
Lagging stand made of series of segments called okazaki fragments that are joint together by DNA ligase
what are the limitation of DNA polymerase in linear DNA
The usual replication
machinery provides no
way to complete the 5’
ends, so repeated rounds
of replication produce
shorter DNA molecules.
function of telomeres
do not prevent the shortening of DNA molecules, but they do postpone the erosion genes near the ends of DNA molecules
