What is molecular Genetics?
The study of DNA & RNA structure and function on a molecular level.
_____ is the repeating structural unit of nucleic acids.
What are the three components of a nucleotide?
- Phospate group
- Pentose Sugar
- Nitrogenous base
What is the difference between Deoxyribose and Ribose sugars?
Deoxyribose lacks a hydroxyl group at the 2' position when compared to ribose.
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)
What is a Nucleoside?
A compound where the based is attached only to the sugar. (can be deoxyribose or ribose)
A nucleotide is a nucleoside with one or more phosphates groups covalently attached to _____ and/or _____.
In the structure of a nucleotide, the base is attached at the _____ carbon and the phosphate groups are attached to the _____ carbon.
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.
What gives DNA and RNA it's negative charge?
The backbone of both are negatively charged due to the charge on each phosphate.
Describe the directionality of strand building of DNA.
- Based on the orientation of the sugar 5' to 3'
Nucleotides within a strand are _____ attached to each other, which prevents them from shuffling.
Who is Linus pauling?
Proposed the alpha helix as a secondary structure of some proteins.
Who is Erwin Chargaff?
worked with the chemical composition of DNA; discovered the amount of A=T and C=G.
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.
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.
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.
What is the AT/GC rule (Chargaff ' s rule)?
Purines (A&G) always bond with Pyrimidines (T&C).
How many hydrogen bonds exist between G&C? And A&T?
What is a groove?
Indentation where the atoms of the bases are in contact with surrounding water.
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.
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.
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.)
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.
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.