CELS 191 Lecture 13 Flashcards
DNA is always synthesised in the 5’ to 3’ direction. therefore the parental template strands are said to be read/run in the ______direction
3’ to 5’
humans have ___ pairs of large linear chromosomes
23
true or false: DNA replication has multiple origins and is unidirectional
false - replication has multiple origins and is BIDIRECTIONAL
humans have about 2 meters of DNA in each cell if you pull it out and line it up. because of this there needs to be multiple points of relocation along the chromosome what are these points called
origins of replication
what is the name of the place where DNA replication is actively happening
the replication fork
what are origins of replication
where we are going to start to split the DNA apart - they all have TATA boxes to make splitting the DNA easier
what are the names of the places where DNA has been split apart for replication
replication bubbles
what is needed to make a DNA copy
progressive addition of new nucleotides
a starting point for nucleotide addition
unwinding of the helical double stranded DNA
release of tension generated by the unwinding DNA helix
prevention of unwound double-stranded helical DNA
joining of ends of newly synthesised fragments together
how is the leading strand synthesised
continuously in its 5’ to 3’ direction
how is the lagging strand synthesised
discontinuously in its 5’ to 3’ direction as Okazaki fragments
that is primase
primase is an enzyme (not Ann enzymatic function of polymerase), a type of RNA polymerase that’s makes an RNA primer. primer will act as a starting point for DNA polymerisation
can DNA polymerase 3 bind to a single stranded DNA and start copying it
no
what does DNA polymerase 3 need in order to start DNA synthesis
an OH group into which the phosphate group of the incoming nucleotide can be attached
what is the name of the enzyme that synthesises a new DNA strand by adding nucleotides complementary to the parental template strands
DNA polymerase 3
what is the first step in DNA replication
helicase pulls the two strands apart
why are single stranded DNA binding proteins needed during DNA replication
they protect the DNA from being degraded as well as preventing the strands which have complementary bases from snapping back together
what is the function of primase in DNA replication
after the single stranded binding proteins are attached the primase introduces an RNA primer in the 5’ to 3’ direction
what do we have on the 5’ and 3’ ends of DNA
3’ has a hydroxyl
5’ has a phosphate
what enzyme adds nucleotides one at a time to the 3’ end of the RNA primer
DNA polymerase 3
what happens when DNA polymerase 3 runs into a single stranded binding protein
it physically pushes it off
what is the function of of DNA polymerase 1 in DNA replication
is recognises the RNA-DNA hybrids and degrades the RNA component and uses it’s polymerase activity to fill the gap using the 3’ hydroxyl group on the next Okazaki fragment
what is the function of DNA ligase in DNA replication
it joins together the newly synthesised Okazaki fragments - creates a phosphodiester bond - it also joins together the newly synthesised fragments from the multiple replication bubbles including the leading strands
what is the function of topoisomerase is DNA replication
it is used to unwind/release the supercoil in the DNA strands
what is a nuclease
an enzyme that can break down RNA or DNA
