translation and transcription Flashcards
Griffith’s experiment
step- by- step
he used 4 different treatments on mice and saw how they reacted to each
worked with two strains of bacteria
one pathogenic(S cells) and one harmless(R cells)
when he gave a mouse living S pathogenic cells it dies
when he gave a mouse living R, nonpathogenic cells, it lived
mice given heat killed S cells, survived
lastly, he gave mice a mixture of heat-killed S cells and living R cells
mice died
the heat killed remains of the pathogenic strain made some of the living non pathogenic cells become pathogenic
called this transformation
hershey-chase experiment
Radioactive sulfur was used to determine if proteins carried genetic material and radioactive phosphorus was used to determine if DNA used genetic material
experiment tested which macromolecule was going to enter into the bacteria and act like a blueprint for more phage(which carries the genetic material to facilitate this)
result: dna entered and the protein stayed outside the bacteria so dna has to be the genetic material
hershey-chase experiment
step by step
two different batches of experiments
one batch where phage were labeled with radioactive protein and another with radioactive DNA
the phage were allowed to interact with bacteria cells and centrifuged to be detached once done
then the material found in bacterial cells were determined (whether protein or dna entered)
If we conducted the Hershey-Chase experiment again using radioactive N15, where would you expect to find the radioactive signal (and what part of the macromolecule is being labelled?
both inside the bacteria and outside the bacteria since both protein and dna macromolecules contain N
why do cells divide
growth
repair
to reproduce
conservative model of dna rep
idea that both of the parental strands remained after replication
the parental dna strands acetic as a template for daughter strands and then reassembled into original parent double helix
after second replication = three daughter double helix’s and one parental double helix
semiconservative model
the true model of dna rep
the two parental strands separate and each individual strand acts as a template for the synthesis of a new complementary strand
after first rep, two double helix’s each with one parental strand and one daughter strand
after second rep, two double helix’s with one parental one daughter strand, and then two double helix’s with just daughter strands
dispersive model
replication results in strands of dna with a mixture of both daughter and parental strand sections
sections of daughter and parental strands after replication
meselson-stahl experiment
bacteria cultured in medium with 15N(heavy isotope) was transferred into a medium with 14N(lighter isotope)
DNA sample was centrifuged after the first replication and there was one weighted band of DNA
DNA sample centrifuged after the second replication revealed two bands, one heavier weighted band and one lighter weighted band
semi conservative model is the only model that would have one band in the first replication and two in the second
Looking at the experimental result after the first replication of the DNA, where there is one uniform weighted band of DNA, what model of DNA replication can be ruled out?
conservative
where does DNA replication start
at origins of replication
- short section of DNA with specific sequence of DNA
proteins that recognize these sequence attach to the DNA to separate the two strands, opening a replication bubble
replication fork
replication of DNA proceeds in both directions after the two dna strands are opened and create a replication bubble
each end of the replication bubble has a replication fork where DNA is being unwound to enable replication
what does the extension of the polymer of nucleic acids require
a dehydration reaction per each monomer added
the dehydration reaction between each nucleotide monomer results in the lengthening of DNA strand, and a phospho-dyester bond between each monomer
DNA polymerases
responsible for catalyzing the formation of the phosphodiester bond
add nucleotides to chain of dna strands
can only read/move from 3’ to 5’ direction (adds from 3’ to 5’)
can only add a new nucleotide at the 3’ end
requires a primer to start adding nucleotides
how does dna replication begin
helical unzips/unwinds DNA and creates replication fork
topoisomerase releases tension from the helicase unzipping DNA so that the DNA strands don’t break apart
single-strand binding proteins act as anchors to hold DNA open
primase attaches to parental strand to write the RNA primer that DNA polymerase can attach to
the leading strand
dna polymerase III attaches to the RNA primer and moves from 3’ to 5’ on the parental strand to add nucleotides to primer
creates a continuous 5’ to 3’ daughter strand towards the replication fork
the lagging strand
dna polymerase moves from 3’ to 5’ on the parental strand so for the lagging strand its moving away from the replication fork
makes okazaki fragments
dna polymerase iii attaches to rna primers and detaches once it reaches another rna primer ahead of it on the parental strand
dna polymerase i replaces the rna primer fragments with dna
dna ligament forms bonds between the dna fragments
purpose of telomerase
every time you replicate DNA you lose a chunk of DNA at the end
when a DNA strand gets too short, it signals the cell to die —> apoptosis
some cells need to keep being replicated to keep us functioning
avoid damage to such DNA and DNA shortening by making sure the strands don’t get too short
Telomerase is the enzyme responsible for replacing the DNA that is lost to replication
telomeres —> arms of DNA that telomerase is adding DNA to
