Nucleic Acids Flashcards
Name the Purine Bases
Adenine, Guanine
Name the Pyrimidine Bases
Cytosine, Thymine, Uracil
Name the constituents of a Nucleotide. How does that differ from a nucleoside?
Nucleotide = Nitrogenous Base + Pentose + Phosphate; Nucleoside loses the phosphate group
What is more soluble, pyrimidine or purine?
Pyrimidine
What two diseases are due to accumulation of purines in tissue due to insolubility?
Gout (uric acid buildup in joints) and Lesch-Nyhan (severe neurologic symptoms)
What two groups on neighboring nucleotides makes up the phosphodiester linkage?
5’ Phosphate and 3’ Hydroxyl groups in the 5’-3’ orientation
Explain the experiment that established DNA as the genetic material.
Avery, McCloud, McCarty: Heat-Killed virulent strain pneumococcus mixed with non-virulent pneumococcus still killed mice. There must be something that transferred between them.
Explain what Rosalind Franklin and Maurice Wilkins did.
Took X-Ray crystallography of DNA, and showed its structure.
Explain what Watson and Crick did, and explain the shape of their model.
Solved the DNA 3D structure: right-handed, Double-stranded Helix, sugars on the outside, bases on the inside (pairing to each other).
What are the three chargaff rules?
Total Purines and Total Pyrimidines are roughly equal, A=T and G=C, and GC/AT ratios differ among organisms.
Which Bonds are stronger? G=C or A=T
G=C. Its because they bond three times!!!
Does increased salt concentration increase or decrease the stability of DNA?
Increase! The ions stabilize charge on the phosphate groups.
What is supercoiling in DNA?
Think grandma’s phonecord. Its already spiraled, but now it twists as well! Those twists are supercoils
What type of base does methylation generally occur in DNA, and how does it affect activity?
5’ Cytosines of CpG sequences causing decreases to gene activity
What agent causes deamination, and what is our greatest concern in deamination?
Nitrous acid; C-T caused by deamination of a methylated cytosine, creating Thymine.
Whatrepair mechanism repairs deamination?
Base Excision Repair
Why is depurination such a big worry, and what repairs it?
Depurination can cause weakness in the phosphodiester backbone, and with too much, breaks in the DNA backbone.
What affect does UV-radiation have on DNA?
Cross-linking of thymines to thymine-dimers (cyclobutane), causing kinks.
What repair mechanism is used for thymine dimerization?
Nucleotide Excision Repair and TFIIH
What are three major differences between DNA and RNA?
DNA has no 2’-OH, uses Thymine, is double stranded, and is more stable. RNA is hydroxylated at the 2’ position, uses uracil, and is single stranded.
Name the structural RNAs.
rRNA (ribosomal), tRNA (transfer), snRNA (small nuclear) and snoRNA (small nucleolar)
Name the Regulatory RNAs.
miRNA (micro), siRNA (small interfering)
Name the information-containing RNAs.
mRNA (messenger)
How do we attempt to utilize properties of Cancer against itself?
If we use intercalating agents, we can stop DNA synthesis in cancer cells
How do we stop transcription in cancer cells?
Targeting topoisomerases allows us to bind up the factor required to relax DNA to allow transcription.
How does Puromycin work?
Puromycin respembles 3’ end of aminoacyl tRNA and enters the A-site of transcription to cause premature chain release.
