DNA Structure and Function

Question 1

What are the types of nucleic acids?

Answer 1

DNA
RNA

Question 2

What type of bonds hold deoxynucleotides together?

Answer 2

Phosphodiester Bonds

Question 3

Where is DNA located in humans?

Answer 3

Chromosomes
Mitochondria

Question 4

What are the forms of DNA in prokaryotes?

Answer 4

Chormosomes
Non-chromosomal DNA (e.g. plasmids)

Question 5

What are the functions of DNA?

Answer 5

Storage and Transmission of Genetic Information
Control Selective Protein Synthesis

Question 6

Outline of the central dogma

Answer 6

DNA can replicate itself
DNA is transcribed to RNA
RNA is translated to form proteins

Question 7

Primary structure of DNA

Answer 7

Sequence of nucleotide bases which are covalently linked by 3’~5’ phosphodiester bonds

Question 8

Purines

Answer 8

Double ring nitrogenous bases
Adenine and Guanine

Question 9

Pyramidines

Answer 9

Single ring nitrogenous bases
Cytosine and Thymine

Question 10

Describe the polarity of the DNA 1ry structure

Answer 10

Free phosphate group at 5’ end binds to OH group at the other 3’ end

Question 11

Secondary structure of DNA

Answer 11

Two polynucleotide chains wrapped around one another to form a double helix

Question 12

How many base pairs does each turn contain?

Answer 12

10 base pairs

Question 13

DNA associated with protein is called …

Answer 13

nucleoprotein

Question 14

Chargaff Rule

Answer 14

In a DNA sample:
1. Adenine equals Thymine
2. Guanine equals Cytosine
3. Purines equals Pyrimidines

Question 15

Number of H-bonds between adenine and thymine

Answer 15

2 electronegative atoms

Question 16

Number of H-bonds between cytosine and guanine

Answer 16

3 electronegative atoms

Question 17

Major and Minor Grooves

Answer 17

Question 18

What causes major and minor grooves?

Answer 18

Difference in size due to asymmetry of deoxyribose rings
Structurally distinct nature of upper surface of base-pairs relative to the bottom surface

Question 19

Purpose of major and minor grooves

Answer 19

Provide access for binding of regulatory proteins

Anticancer drugs such as dactinomycin bind to these regions

Question 20

What factors stabilize the DNA helix?

Answer 20

Stacking Interaction of bases by hydrophobic interactions between bases
Hydrogen Bonds between nitrogenous bases

Question 21

Polymorphism of DNA

Answer 21

B-DNA
A-DNA
Z-DNA

Question 22

Differences between the types of DNA

Answer 22

Question 23

Tertiary Structure of DNA

Answer 23

Three-Dimensional shape of Nucleic Acid polymer

Question 24

Which DNA has a Double Stranded Linear 3ry structure?

Answer 24

Eukaryotic Nuclear Chromosomes

Question 25

Which DNA has a Double Stranded Circular 3ry structure?

Answer 25

Mitochondrial
Plasmid
Viral
Chloroplast

Question 26

What is denaturation?

Answer 26

Separation of DNA strands by disruption of H-bonds

Question 27

What factors lead to denaturation?

Answer 27

Change in pH
Heating

Question 28

Why does changing pH cause denaturation?

Answer 28

Causes ionization of bases
Disruption of H-bonds

Question 29

Why does heating cause denaturation?

Answer 29

Heating disrupts H-bonds

A-T base pairs are less stable than G-C base pairs

Question 30

What is Melting Temperature (T_M)?

Answer 30

Temperature at which 50% of DNA molecule exists as single strand

Question 31

How can DNA denaturation be measured?

Answer 31

Measuring absorbance at 260nm
Single stranded DNA has a higher relative absorbance at this wavelength

Question 32

What is renaturation?

Answer 32

Cooling enables complementary base pairs to reform double helix