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genes were known to be associated with specific traits and that mutations can alter gene function, the one gene one enzyme hypothesis (genes determine the structure of proteins), genes are carried on chromosomes, chromosomes are made of DNA and protein, DNA is the genetic material
what 5 things were known about DNA and genes before the structure of it was known
bacterial transformation (heated kill S bacteria with live R bacteria killed the mouse)
what did Frederick Griffith discover
DNA is the genetic material in bacteria
what did Avery, MacLeod, and McCarty discover
virulent S cells lost its ability to be transformed when the DNA in the mixture was destroyed and no live S strain was recovered
how did Avery, MacLeod, and McCarty discover that DNA is the genetic material
DNA is the genetic material in phage
what did the Hershey-Chase experment prove
they incorporated radioactive 32P into DNA and 35S into proteins of separate phage cultures. 32P was found inside the infected bacterial cells while 35S remained in the phage ghosts
how did Hershey and Chase confirm that DNA is the genetic material in phage
must allow accurate replication, must have information content (encode proteins), must be able to change on rare occasion
what are three key properties of hereditary material
a phosphate, a sugar, and one of 4 nitrogenous bases
what are the building blocks of DNA (deoxynucleotides)
a sugar and a nitrogenous base
what is a nucleoside made of
rules of base composition: the total amount of purines equals the total amount of pyrimidines, there are equal amounts of A + T and G + C
what did Chargaff find
the X-ray diffraction pattern of DNA showed that it is a long and skinny, double helix
what did Rosalind Franklin find
they knew that A pairs with T and G pairs with C from Chargaff and this supports the diameter of a double helix found by Rosalind Franklin as a purine with a pyrimidine leads creates that diameter leading to the proposed model of DNA
how did Watson and Crick combine what was already known about DNA to propose a structure for it
hydrogen bond
what bond forms between the purine and pyrimidine bases of each strand in a DNA double helix
phosphodiester linkage
what bond forms between the alternating phosphate and deoxyribose sugar units that compose the backbond of each strand in a DNA double helix
5’ carbon of one deoxyribose to the 3’ carbon of another deoxyribose
what carbons does a phosphodiester bond attach in the backbone of a DNA double helix
phosphate group
what does the 5’ end of a DNA strand end with
hydroxyl
what does the 3’ end of a DNA strand end with
3
how many hydrogen bonds do G-C base pairs have
2
how many hydrogen bonds do A-T base pairs have
one parental DNA helix containing nucleotides of one density replicated with nucleotides of a lighter density. After one round of replication each strand had an equal mix of N14 and N15 nucleotides and after the second round there were two strands with N14 and N15 and two strands with only N14 proving replication is semiconservative
how did the Meselson-Stahl experiment work
replicating DNA in bacterial cells incorporated tritiated thymidine (a nucleoside labeled with a radioactive hydrogen isotope). When analyzed a ring of block spots appeared looking like a loop of DNA and when analyzed during replication a theta was observed thus proving replication forks (and origins of replication) in bacterial DNA
how did the Cairns experiment work
helicase
what protein opens the helix in DNA replication
topoisomerase
what protein prevents overwinding in DNA replication
2 nm
what is the diameter of a DNA double helix
Bind DnaA protein to DnaA box at oriC locus, open at AT rich region, bind DnaB protein (helicases), assemble replisome, synthesize DNA and forks move
steps of initiation of replication in bacteria
single-strand DNA binding proteins
what stabilizes unwound DNA in bacteria replication
origin of replication
where does the replisome assembly at in a bacterial cell
5’ to 3’
in what direction does DNA replication occur
catalyzes DNA chain growth in the 5’ to 3’ direction, a 3’ to 5’ exonuclease activity that removes mismatched nucleotides, a 5’ to 3’ exonelcease activity that degrades single strands of DNA or RNA (too slow and not processive)
functions of DNA polymerase I
primer
a short chain of nucleotides that forms a segment of duplex nucleic acid
synthesized by a set of proteins called a primosome
primase
what is the central RNA polymerase component of a primosome
DNA polymerase I
what DNA polymerase removes RNA from okazaki fragments and fills and proofreads gap
DNA polymerase III
what DNA polymerase replicates DNA and proofreads at fork
5’ to 3’ polymerase activity that adds nuclotides, 3’ to 5’ exonuclease activity that removes nucleotides
what are the functions of DNA polymerase III
ligase
what enzyme joins the 3’ end of the gap-filling DNA to the 5’ end of the downstream Okazaki fragment
semidiscontinuous
DNA replication is ___ because it has both a leading and lagging strand
primase synthesizes short RNA primers using DNA as a template, DNA polymerase III synthesizes DNA starting at the 3’ end of RNA primers, DNA polymerase I removes RNA primers and fills the gap, DNA ligase connects adjacent DNA fragments
steps in DNA synthesis
many
does eukaryotic DNA replication have one or many origins of replication
synthesis (s)
what phase of a eukaryotic cell cycle does DNA replication occur
11 basepair consensus sequence binds to the origin recognition complex, helicase binds, opens helix at neighboring AT rich region and helicase slides down, DNA polymerase binds
steps for initiation of eukaryotic DNA replicationt
telomere
the end of a chromosome
a terminal gap forms because DNA replication requires a primer upstream
what is the telomere problem
telomerase anneals to the 3’ terminal gap, this overhang is extended via the RNA contained in the telomerase and the reverse transcriptase protein, primase and DNA polymerases then use the 3’ overhang as a template to fill in the other end of the DNA strand
the steps of telomere formation
reverse transcriptase, it uses RNA as a template to synthesize DNA
what type of DNA polymerase is telomerase
telomeric loop
a protective structure that sequesters the 3’ single-stranded overhang to avoid it being mistaken for a double-stranded break
somatic cells contain very little telomeres so they shorten as the body ages and has been linked to premature aging
why are telomeres likely related to aging
