Studied by 56 people
answer with defination
What was the Hershey-chase experiment
They determined that inside genes/cells there was DNA and not proteins by injecting radioactive material into the genes that either would show proteins (35S tag) or DNA (32P tag) of which DNA was present
what are the three components of a nucleotide
phosphate group (5’ end), a nitrogenous base (A,T,C,G) and a sugar (3’ end)
how does complementary base pairing work
A with T
C with G
connected together via hydrogen bonds. there is a template strand that is created which allow for these new bases to be added on
what holds the nucleotides together
phosphodiester bonds
what are the names for the 2 strands of DNA
Parental (template) and daughter strand
why is DNA antiparell
it has 2 strand that run in the opposite direction. one runs 5’→3’ while other runs 3’→5’
what were the three types of DNA syntheses that were looked at to determine how DNA replication occurs
semiconservative replication
conservative replication
dispersive replication
what is semiconservative replication
parental stand separates (unzips) and each on the strand is used as a template foe a new strand
now it has one old strand and one new strand
what is the conservative replication
the parental model serves as a template for an entirely new strand
one daughter has 2 old strand while other has 2 new strands (like cloning)
what is the dispersive replication
the parental strand cuts into sections
one strand has parts of new and old intertwined
what model for DNA replication was supported
semiconservative replication model
what shape does DNA make
double helix
how many replication bubbles does bacteria have
one because it is circular DNA
how many replication bubbles does DNA have
as many as it wants cause it is one long strand
what is the replication fork
location at which the bubble end meets the DNA that is not untwisted yet by helicase
what does DNA helicase do
unzips the DNA parent strand and creates the replication bubble by breaking the hydrogen bonds
what are the SSBPs used for
attach inside he replication bubble that is formed to help keep it open. stabilizes the structure
what does topoisomerase do
while the bubble gets formed, tension is in the still coiled DNA and it cuts and rejoins the DNA to help release this tension. also helps keep the DNA from breaking
what does DNA polymerase do
this is what physically makes the new daughter DNA strand by attaching the new nucleotide bases to its correct match. It only works in the 5’→3’ direction and needs primers to tell it where to start
what does primase do
it places primers on the leading and lagging strand to tell DNA polymerase where to start working at
on leading strand, it only needs to place one primer and it will work continuously
on the lagging strand, it has to place multiple primers as DNA polymerase has to work in the “opposite direction” then DNA is getting unzipped. has to keep moving backwards
what doe DNA ligase do
it glues the Okazaki fragments that are made on the lagging stand together
what is the leading strand
the strand that gets build in the 5’→3’ direction. gets made in one continuous motion
what is the lagging strand
the strand that gets built in the 3’→5’ direction. has to get made in many small fragments called Okazaki fragments
what is the replisome
multiprotein molecular machinery responsible for the replication of DNA
what is a telomere
a tail that is created on the end of the parent strand of DNA where new DNA is not make on the daughter stand. these are caused from the lagging strand getting made in pieces
this is problematic as the DNA keeps getting shorter
what is an example of a telomerase
cancer cells as it allows them to keep growing
what is responsible for proofreading the DNA
DNA polymerase
what error does UV light cause
production of an extra thymine (thymine dimers) which cause a kink in the DNA
What is nucleotide excision repair
fixes errors that occur within the DNA by recognizing the error then removing the damaged section
what is the central dogma of biology
DNA→ RNA→ proteins
who discovered the mRNA was found carrying a copy of the DNA message
Jacob and Monod
what does RNA polymerase do
synthesizes RNA (makes the RNA via the DNA)
what scientist discovered that there was 64 3 codon code for reading the mRNA template strand
Gamow and then Crick and Brenner confirmed
what occurs between DNA and RNA
transcription - making a copy of the information
what occurs between RNA and proteins
translation - interpreting language into proteins
where does transcription occur in eukaryotes
in the nucleus
where does translation occur for eukaryotes
in the cytoplasm
what is a codon
a triplet code that codes for a certain protein. there are 64 possible codons for the 20 amino acids. several codons code for the same amino acid
where is the codon located on
the mRNA strand
who assigned what each codon coded for
Nirenberg and Leder
how does DNA help create the message for these codons
the DNA holds all the information of which the RNA strand is built off of. The DNA base pairs are translated into the RNA base pairs of which now allows the codons to be read to code for the proteins
what is the start codon
AUG (methionine)
what are the stop codons
UGA, UAA, UAG
what does the genetic code entail (4)
redundant - more than one codon for amino acids
unambiguous - only one codon for only that AA
nearly universal - shared by all organisms
without punctuation - no breaks in-between the code
what is it called when information flows backwards from RNA back to DNA
reverse transcriptase which is problematic
define point mutation
one or a a small number if base changes that occur. they are permeant changes to the DNA
what are the types of point mutation and define all (4)
Missense mutations - change an amino acid in the protein. codes for wrong amino acid
silent mutations - does not change what amino acid gets coded for from reduadancy
frameshift mutations - shift the reading frame altering all the following codons (base gets added or removed)
nonsenses mutations - change in codon that codes for a stop codon when it should not
how do point mutations impact the fitness of an organism (3) and what are most common
1. beneficial - increase the fitness of the individual
2. neutral - have no effect on the individual
3. deleterious - mutations decrease the fitness of the organism
most of the point mutations are neutral or deleterious
what are the chromosome mutations and their definitions (4)
Inversion - segment breaks off of chromosome, flips around and rejoins on
Translocation - a section breaks off and reattached to another chromosome
Deletion - a segment of chromosome is lost
Duplication - a segment is present in may copies
How can chromosome mutations be seen
karyotype
what does transcription do
RNA molecule is made from DNA in a similar fashion that DNA replication is done. Only the template strand is needed in order to create the RNA molecule
decodes the message hidden in DNA into RNA
How does the RNA polymerase work
De novo - does not need template strand to get going
what much attach to the DNA in bacteria before it can start having an mRNA strand built off of it
a sigma must bind
what are the three stages of transcription and translation
initiation, elongation, termination
describe what happens in initiation in transcription
the RNA polymerase attaches to the promoter (part of the DNA that allows the RNA polymerase to attach before the part that gets coded)
describe what happens in elongation in transcription
the RNA strand starts to be be build and grows longer. As it grows longer it peals away from the template strand and exits the RNA polymerase. The DNA now recoils and exits the polymerase too
describe what happens in termination in transcription
the RNA polymerase reaches a set of bases in the DNA template called the terminator which tells it to stop coding. the RNA polymerase detaches from the DNA and the new RNA molecule
what is mRNA
Messenger RNA which is the carrier of information that encodes the amino acid sequence. (this was the RNA that was created in transcription)
besides the code for the amino acids what is mRNA made of
introns (white noise) and exons (physical code)
what is the process of removing the introns
RNA splicing via spliceosomes
explain the process of RNA splicing
introns are removed via spliceosomes, a cap is placed on the 5’ end and poly A-tail are placed on the 3’ end. this is no the completed mRNA molecule ready to go to translation
how is transcription different in prokaryotes and eukaryotes
prokaryotes - a sigma is required for the RNA polymerase to bind to the promoter. it allow occurs in the cytoplasm which is the same place where translation take place
eukaryotes - occurs in the nucleus and RNA polymerase is able to just bind to promoter
what are ribosomes used for
they are used in the process of translation to take the code out of mRNA to amino acids. comprised of a small and large subunit. small subunit attaches to the mRNA
what are polyribosomes
when many ribosomes attach to the same mRNA stand to make the same AA chain more than once
what is tRNA
transfer RNA that uses anticodons to pull the code out of mRNA and make the protein chain
consisted of loops and stem the house the anticodon to the mRNA. additionally has a CCA sequence that is able to grab the corresponding AA to the sequence
what is the anticodon
the opposite code (bases) than is on the mRNA
what is translation
taking mRNA into the amino acid sequence with the use of tRNA in the ribosome
how many tRNAs are there
only 40 because of redundancy. found from crick in the wobble hypothesis
what are the sites that tRNA go into in the ribosome
A site - acceptor site
P site - where peptide bonds form
E site - where tRNA exits
explains what happens in initiation in translation
starts with the AUG codon, the small subunit binds to the mRNA strand via ribosomal binding site (rRNA) upstream of start codon, large subunit attaches on top, a tRNA is in the A-site and starts to move to the P-site
explains what happens in elongation in translation
tRNA works its way through the A, P, E sites building the AA chain longer and longer. everything moves one at a time to the empty site (not an all at once movement)
explain what happens in termination in translation
stop codon is reached which NO tRNA codes for but rather a protein aka release factor enters the A site and causes the 2 subunits of ribosomes to detach.
what is translocation
how the ribosome moves down the mRNA strand from elongation factors
after termination in translation, what is the last thing that happens
the amino acid chain is now folded into a protein with the help of molecular chaperones to help complete the chain
Note 
Flashcard (24)