Nucleic Acids

Question 1

Name the Purine Bases

Answer 1

Adenine, Guanine

Question 2

Name the Pyrimidine Bases

Answer 2

Cytosine, Thymine, Uracil

Question 3

Name the constituents of a Nucleotide. How does that differ from a nucleoside?

Answer 3

Nucleotide = Nitrogenous Base + Pentose + Phosphate; Nucleoside loses the phosphate group

Question 4

What is more soluble, pyrimidine or purine?

Answer 4

Pyrimidine

Question 5

What two diseases are due to accumulation of purines in tissue due to insolubility?

Answer 5

Gout (uric acid buildup in joints) and Lesch-Nyhan (severe neurologic symptoms)

Question 6

What two groups on neighboring nucleotides makes up the phosphodiester linkage?

Answer 6

5’ Phosphate and 3’ Hydroxyl groups in the 5’-3’ orientation

Question 7

Explain the experiment that established DNA as the genetic material.

Answer 7

Avery, McCloud, McCarty: Heat-Killed virulent strain pneumococcus mixed with non-virulent pneumococcus still killed mice. There must be something that transferred between them.

Question 8

Explain what Rosalind Franklin and Maurice Wilkins did.

Answer 8

Took X-Ray crystallography of DNA, and showed its structure.

Question 9

Explain what Watson and Crick did, and explain the shape of their model.

Answer 9

Solved the DNA 3D structure: right-handed, Double-stranded Helix, sugars on the outside, bases on the inside (pairing to each other).

Question 10

What are the three chargaff rules?

Answer 10

Total Purines and Total Pyrimidines are roughly equal, A=T and G=C, and GC/AT ratios differ among organisms.

Question 11

Which Bonds are stronger? G=C or A=T

Answer 11

G=C. Its because they bond three times!!!

Question 12

Does increased salt concentration increase or decrease the stability of DNA?

Answer 12

Increase! The ions stabilize charge on the phosphate groups.

Question 13

What is supercoiling in DNA?

Answer 13

Think grandma’s phonecord. Its already spiraled, but now it twists as well! Those twists are supercoils

Question 14

What type of base does methylation generally occur in DNA, and how does it affect activity?

Answer 14

5’ Cytosines of CpG sequences causing decreases to gene activity

Question 15

What agent causes deamination, and what is our greatest concern in deamination?

Answer 15

Nitrous acid; C-T caused by deamination of a methylated cytosine, creating Thymine.

Question 16

Whatrepair mechanism repairs deamination?

Answer 16

Base Excision Repair

Question 17

Why is depurination such a big worry, and what repairs it?

Answer 17

Depurination can cause weakness in the phosphodiester backbone, and with too much, breaks in the DNA backbone.

Question 18

What affect does UV-radiation have on DNA?

Answer 18

Cross-linking of thymines to thymine-dimers (cyclobutane), causing kinks.

Question 19

What repair mechanism is used for thymine dimerization?

Answer 19

Nucleotide Excision Repair and TFIIH

Question 20

What are three major differences between DNA and RNA?

Answer 20

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.

Question 21

Name the structural RNAs.

Answer 21

rRNA (ribosomal), tRNA (transfer), snRNA (small nuclear) and snoRNA (small nucleolar)

Question 22

Name the Regulatory RNAs.

Answer 22

miRNA (micro), siRNA (small interfering)

Question 23

Name the information-containing RNAs.

Answer 23

mRNA (messenger)

Question 24

How do we attempt to utilize properties of Cancer against itself?

Answer 24

If we use intercalating agents, we can stop DNA synthesis in cancer cells

Question 25

How do we stop transcription in cancer cells?

Answer 25

Targeting topoisomerases allows us to bind up the factor required to relax DNA to allow transcription.

Question 26

How does Puromycin work?

Answer 26

Puromycin respembles 3’ end of aminoacyl tRNA and enters the A-site of transcription to cause premature chain release.