Molecular Biology Midterm Exam 1 2025

Griffith's experiment - Correct Ans-genetic material could be transferred between dead bacteria and living bacteria Avery, McLeod and McCarty - Correct Ans-Proved that DNA is the hereditary material. DNase, Protease, RNase experiment Hershey-Chase Experiment - Correct Ans-confirmed that DNA is the genetic material because only Phosphorous radiolabeled DNA could be found in bacteriophage-infected bacteria (in the pellet) versus the radioactive sulfur labeled protein coats in the supernatant Structure of nucleotides - Correct Ans-5 carbon sugar, phosphate group, nitrogenous base. Phosphate and sugar linked by phosphodiester bonds, bases by H bonds Purine - Correct Ans-Adenine and Guanine, 2 ring Pyrimidine - Correct Ans-Cytosine and Thymine, 1 ring Differences between DNA and RNA - Correct Ans-RNA contains uracil DNA contains thymine DNA has deoxyribose RNA has ribose other roles of nucleotides - Correct Ans-electron carrier, methyl carrier, and for signalling (e.g. NAD+, NADP+, FAD, adoMet, cAMP) DNA structure - Correct Ans-double stranded, antiparallel, helical, with a major and a minor groove. helix of DNA - Correct Ans-10.5 bp per turn in B form DNA, with each bp being 3.4 angstrom or 1/10 nm apart. B-form DNA - Correct Ans--the most common form of DNA in which molecular configuration spirals to the right A form DNA - Correct Ans-Condensed form of DNA. Deeper major groove and shallower minor groove. right handed helix. 11 bp per turn. seen in low water content environments. Z form DNA - Correct Ans-Left-handed helical form of DNA. 12 bp/turn. may form in high salt environments, unclear A-tracts - Correct Ans-sequences of 4-6 As or Ts seperated by Gs and Cs, repeated. This causes bends in the DNA moleclule. incr interaction with proteins, usually transcription factors Inverted repeats - Correct Ans-sequence followed by sequence that is its inverted repeat. form hairpin or cruciform structures. palindrome - Correct Ans-Same sequence on both strands read from 5' to 3' direction. restriction enzyme binding site. RNA structure - Correct Ans-usually A form helix. can form non-typical bps e.g. A-A and G-U. 2'OH allows for more complicated secondary structures. Also can become riboswitches Denaturation - Correct Ans-breaking of H bonds between strands of DNA at high pH or Temperature Annealing - Correct Ans-strands reattach together at neutral pH and temp heteroduplex - Correct Ans-a DNA double helix composed of single strands from two different DNA molecules. used as molecular genetics tool for comparing sequence similarity (northern and southern blotting) northern blotting - Correct Ans-DNA-DNA interaction (as ssDNA) southern blotting - Correct Ans-ssRNA transcript, ssDNA interaction. deamination - Correct Ans-loss of an amino group, e.g. Cytosine deaminated to Uracil. lots of cytosine deaminated but repaired. Methylation - Correct Ans-addition of a methyl group, most often on C and A. makes DNA more compact, roles in DNA repair, and restriction-modification systems. RNA methylation - Correct Ans-at 2' OH, interferes with the extra bonds that it could otherwise form. RNA acetylation - Correct Ans-tend to occur in tRNAs and rRNAs, etc. e.g. acetyl cytidine, inosine, pseudouridine cloning steps - Correct Ans-1) select cloning vector 2) isolate DNA to clone 3) join vector and DNA fragments 4) introduce recombinant vector to host 5) use selective pressure to favor recombinant hosts cloning vector requirements - Correct Ans-origin of replication, selectable marker, cloning sites (1 of each type) types of cloning vectors - Correct Ans-pBR322 (plasmid) BAC (bacterial artificial chromosome) YAC (yeast artificial chromosome) bacterial artificial chromosome - Correct Ans-A large plasmid that acts as a bacterial chromosome and can carry inserts of 100,000 to 300,000 base pairs. low copy, so it has par genes so all daughter cells contain it. yeast artificial chromosome - Correct Ans-A cloning vector that combines the essentials of a eukaryotic chromosome—an origin for DNA replication, a centromere, and two telomeres—with foreign DNA. shuttle vector shuttle vectors - Correct Ans-can exist in several different species restriction enzymes - Correct Ans-Enzyme that cuts DNA at a specific sequence of nucleotides (palindromic sequence). can cut to sticky or blunt ends. transformation - Correct Ans-uptake of foreign DNA from the surrounding environment chemical transformation - Correct Ans-making host cells membranes permeable by heat shocking it and then introducing CaCl2 electroporation - Correct Ans-A technique to introduce recombinant DNA into cells by applying a brief electrical pulse to a solution con