DNA Structure and Function Flashcards
What are the types of nucleic acids?
DNA
RNA
What type of bonds hold deoxynucleotides together?
Phosphodiester Bonds
Where is DNA located in humans?
Chromosomes
Mitochondria
What are the forms of DNA in prokaryotes?
Chormosomes
Non-chromosomal DNA (e.g. plasmids)
What are the functions of DNA?
Storage and Transmission of Genetic Information
Control Selective Protein Synthesis
Outline of the central dogma
DNA can replicate itself
DNA is transcribed to RNA
RNA is translated to form proteins
Primary structure of DNA
Sequence of nucleotide bases which are covalently linked by 3’~5’ phosphodiester bonds
Purines
Double ring nitrogenous bases
Adenine and Guanine
Pyramidines
Single ring nitrogenous bases
Cytosine and Thymine
Describe the polarity of the DNA 1ry structure
Free phosphate group at 5’ end binds to OH group at the other 3’ end
Secondary structure of DNA
Two polynucleotide chains wrapped around one another to form a double helix
How many base pairs does each turn contain?
10 base pairs
DNA associated with protein is called …
nucleoprotein
Chargaff Rule
In a DNA sample:
1. Adenine equals Thymine
2. Guanine equals Cytosine
3. Purines equals Pyrimidines
Number of H-bonds between adenine and thymine
2 electronegative atoms
Number of H-bonds between cytosine and guanine
3 electronegative atoms
Major and Minor Grooves
What causes major and minor grooves?
Difference in size due to asymmetry of deoxyribose rings
Structurally distinct nature of upper surface of base-pairs relative to the bottom surface
Purpose of major and minor grooves
Provide access for binding of regulatory proteins
Anticancer drugs such as dactinomycin bind to these regions
What factors stabilize the DNA helix?
Stacking Interaction of bases by hydrophobic interactions between bases
Hydrogen Bonds between nitrogenous bases
Polymorphism of DNA
B-DNA
A-DNA
Z-DNA
Differences between the types of DNA
Tertiary Structure of DNA
Three-Dimensional shape of Nucleic Acid polymer
Which DNA has a Double Stranded Linear 3ry structure?
Eukaryotic Nuclear Chromosomes
Which DNA has a Double Stranded Circular 3ry structure?
Mitochondrial
Plasmid
Viral
Chloroplast
What is denaturation?
Separation of DNA strands by disruption of H-bonds
What factors lead to denaturation?
Change in pH
Heating
Why does changing pH cause denaturation?
Causes ionization of bases
Disruption of H-bonds
Why does heating cause denaturation?
Heating disrupts H-bonds
A-T base pairs are less stable than G-C base pairs
What is Melting Temperature (TM)?
Temperature at which 50% of DNA molecule exists as single strand
How can DNA denaturation be measured?
Measuring absorbance at 260nm
Single stranded DNA has a higher relative absorbance at this wavelength
What is renaturation?
Cooling enables complementary base pairs to reform double helix
