Genetics Chapter 7

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