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What is molecular Genetics?
The study of DNA & RNA structure and function on a molecular level.
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_____ is the repeating structural unit of nucleic acids.
Nucleotides
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What are the three components of a nucleotide?
- Phospate group
- Pentose Sugar
- Nitrogenous base
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What is the difference between Deoxyribose and Ribose sugars?
Deoxyribose lacks a hydroxyl group at the 2' position when compared to ribose.
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What are the two types of Nitrogenouse bases, what is the difference between them, and what bases fall in each catagory?
- Purines: Have two Carbon rings. (Adenine and Guanine)
- Pyrimidines: have one carbon ring. (Uracil, Thymine, Cytosine)
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What is a Nucleoside?
A compound where the based is attached only to the sugar. (can be deoxyribose or ribose)
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A nucleotide is a nucleoside with one or more phosphates groups covalently attached to _____ and/or _____.
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In the structure of a nucleotide, the base is attached at the _____ carbon and the phosphate groups are attached to the _____ carbon.
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What is a Phosphodiester linkage and how are they formed?
- A linkage between two carbons and phosphate group through two oxygens.
- Formed through successive dehydration synthesis reactions.
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What gives DNA and RNA it's negative charge?
The backbone of both are negatively charged due to the charge on each phosphate.
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Describe the directionality of strand building of DNA.
- Antiparallel
- Based on the orientation of the sugar 5' to 3'
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Nucleotides within a strand are _____ attached to each other, which prevents them from shuffling.
Covalently
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Who is Linus pauling?
Proposed the alpha helix as a secondary structure of some proteins.
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Who is Erwin Chargaff?
worked with the chemical composition of DNA; discovered the amount of A=T and C=G.
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Who is Rosalind Franklin?
X-ray difraction of DNA was consistent with a helical structure and diameter too wide to be only a single stranded helix. She suggested DNA was composed of two or more strands with 10 bases per turn.
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What did James Watson, Francis Crick, and Maurice wilkins do?
put together the pieces and were awarded the 1962 nobel prize for discovery of the double helix DNA molecule.
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What are the key features of the DNA Helix?
- Double (two strads twisted together around a common axis)
- There are 10 bp within a complete twist (360 around the backbone)
- Double strand is stabilized by hydrogen bonding between base pairs.
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What is the AT/GC rule (Chargaff ' s rule)?
Purines (A&G) always bond with Pyrimidines (T&C).
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How many hydrogen bonds exist between G&C? And A&T?
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What is a groove?
Indentation where the atoms of the bases are in contact with surrounding water.
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What is BDNA?
- Predominant in living cells.
- 10 base pairs per 360.
- Bases tend to be centrally located.
- Hydrogen bonds between base pair occur relatively perpendicular to central axis.
- Right handed.
- Watson and Crick.
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What ia ADNA?
- Right handed.
- 11 base pair per 360.
- Hydrogen bonds between base pair are substantially tilted and relatively central to axis.
- Occurs under low humidity conditions.
- Not biologically significant in DNA.
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What is ZDNA?
- Left handed.
- 12 base pairs per 360.
- Substantially tilted hydrogen bonds between base pairs.
- Occurs at high ionic strength (high salt concentration).
- Favored by sequence that alternate between purines and pyrimidines.
- At lower ionic strength methylation of cytosine bases favors ZDNA.
- Recently determined to be biologically important (only in rare cases, acting as an editor for certain genetic messangers.)
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What is Triplex DNA?
- Triple helix.
- Synthetic DNA binds into the major grooves of natural double stranded DNA in a sequence specific way.
- T in synthetic DNA will bind to an AT pair in the natural DNA strands and C in Synthetic DNA binds to a GC pairing site in natural DNA.
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What is the structure of RNA?
- Shorter than DNA.
- One strand of DNA is used as a template to make one complementary copy of single stranded RNA during transcription.
- Can become double stranded.
- Secondary structures are important to the function of RNA.
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