Nuclei Acids

Question 1

What is a nuclei acids structure and how formed

Answer 1

• poly nucleotides essential for all forms of life
• present in 2 forms ( DNA and RNA )
• sugar phosphate bound at phosphodiester bond
• condensation reaction using up ATP
• phosphate bond on 5’ of one sugar and 3’ of another

Question 2

Nuclei acid polarity

Answer 2

5’ end has phosphate and 3’ -OH- so has polar ends

Question 3

DNA structure and function

Answer 3

• Polynucleotide which forms chemical basis for hereditary. -Genetic info codedd along length of DNA molecule
• 2 antiparallel but complimentary nucleic acids stands coil around common axis forming a double helix structure.
• complimentary bases form as many H2 bonds with each other as possible

Question 4

DNA supercooling, types and enzyme mediator

Answer 4

• twisting of DNA molecules into a more compact form
• positive - DNA twisted by topoisomerase In direction of helix. Bases held more tighter
• negative - DNA twisted in opposite direction ( bases came apart more easily )

Question 5

Double helix forms

Answer 5

1 Z form - left handed, deep minor groove and major hardly existent 12 base pairs per rotation. Depxyribo phosphate backbone zig zags. Found naturally in DNA in regions with tandem Purins and pyrimidins eg poly GC

2 A form - right handed , common for RNA , deep minor groove, shallow major groove, favored in low water conditions. 11 bases per turn. Planes of bases tilted 20 degrees to the perpendicular to helix. Formed by moderately dehydration of B form

3 B form - right handed , smooth backbone. Common form. 10 bases per turn. Planes of bases perpendicular to helix axis

Question 6

Basic Building blocks of Nuclei acids

Answer 6

1 pentase - ribose or deoxyribose

2 Bases - Purines ( 2 rings ) of pyrimidines ( 1 ring )

3 inorganic phosphates

Question 7

Nucleosides

Answer 7

-covalent linkage is base to sugar

Question 8

Nucleotide

Answer 8

-phosphate added to sugar of nucleoside

Question 9

Use of grooves in DNA

Answer 9

Provide access for the binding of regulatory proteins to their specific recognition sites along DNA chain

Question 10

How does anti-Cancer drugs work

Answer 10

-they intercalate into minor groove inhibiting RNA synthesis and subsequently protein synthesis or replication

Question 11

Example of anti-cancer drug

Answer 11

Actinmysin D

Question 12

Separation of dsDNA and causes

Answer 12

-when the H2 bonding between bases is disrupted

• heat breaks the bonds
• if PH is altered such that the bases ionize

Question 13

What is melting temperature Tm

Answer 13

Temp at which 1/2 of he helical structure is lost

Question 14

What is DNA denaturation

Answer 14

-loss of helical structure of DNA through disrupting of H2 bonding