Part 1- DNA Structure

Question 1

DNA, RNA and Proteins

Answer 1

DNA- Stores Information
RNA- Filter and transmit information
Proteins- Execute information

Question 2

Types of Nucleic Acid

Answer 2

• Ribonucleic acid (RNA)
• store of genetic information in some viruses
• Intermediary between DNA and protein
  synthesis
• messenger and structural for translation
• Deoxyribonucleic acid (DNA)
• store of genetic information (blue print) in all
  cellular forms of life and in some viruses

Question 3

Exampoles of Half Lives

Answer 3

mRNA half-life in Salmonella enterica – less than 1 min
mRNA half-life in Humans – around 10 hours
DNA half-life = 521 years

Question 4

Building Blocks

Answer 4

Sugar + nitrogenous base = nucleoside
Sugar + nitrogenous base + phosphate = nucleotide

Question 5

The two structural forms of 2’-deoxyribose

Answer 5

• Fischer Structure (linear)
  -Haworth Structure (Ring)

Question 6

Nitrogenous Bases

Answer 6

Purines: two carbon-nitrogen
rings (A and G)
Pyrimidines: a single carbon-
nitrogen ring (C, T and U)

Question 7

Hydrogen Bonding

Answer 7

hydrogen bond is an
interaction in which a
hydrogen atom bridges
two electronegative
atoms (in biological
systems, usually
nitrogen or oxygen).

Hydrogen Bonds is an intermolecular force (IMF) that forms a special type of dipole-dipole attraction when a hydrogen atom bonded to a strongly electronegative atom
exists in the vicinity of another
electronegative atom with a lone pair
of electrons

*Purine to pyrimidine base pair
width is the same
* Keeps DNA molecule width
consistent
* G - C H bonds stronger
* 3 H bonds between G and C
* 2 H bonds between A and T

Question 8

Joining Nucleotides Together

Answer 8

Phosphodiester Bond
Unit length = base pair (bp)
1000 bp = 1 kilobase pair (1 kb)
1 000 000 bp = 1 megabase pair (1Mb)
DNA molecules > 1 Mb
Chromosome 1 = 247 Mb

Question 9

DNA Double Helix

Answer 9

• Ordered and regular
  structure externally
• Base pairing central to the
  helix
  Because the two glycosidic bonds are not diametrically opposite each
  other, each base pair has a larger side that defines the major groove
  and a smaller side that defines the minor groove. The grooves are lined
  by potential hydrogen-bond donors (blue) and acceptors (red)

Question 10

Complimentary base pairing and replication

Answer 10

Complementary base pairing
provides a means for making
two copies of a double helix

Question 11

Histones

Answer 11

Histones = core of
nucleosomes:
DNA winds around octamer
of histones
DNA held in place by
another histone (H1) – a
group of proteins
Histone packaging reduces
~ 4cm DNA to ~ 0.67 cm

Question 12

Higher Level Packaging

Answer 12

• Nucleosomes packed further together
• Structures are proposed
• Final level of structure
  = chromosome
  seen during cell division

Question 13

Bacteria

Answer 13

1)Circular Chromosomal DNA
2)Formation of looped chromosomal DNA with associated proteins (has looped domains)
3)Supercoiled and looped DNA