Class 7: DNA structure and DNA replication Flashcards
central dogma of molecular biology
3 components of nucleotide
nitrogen base
carbon suger (deoxyribose)
phosphate group
Describe the difference in end of a nucleic acid
- one end has a phosphoryl group attached to the 5’ carbon atom of the sugar
- one end has s free hydroxyl attached to the 3’ carbon of the sugar
in what directions are nucleic acids written
5’ to 3’
are DNA molecules long or short
they are usually extremely long, some consisting of more than 1 billion nucleotides
how is the DNA double helix stabilized
hydrogen bonds + and hydrogen stacking
- edges and base pairs make hydrogen bonds
- planar surfaces are hydrophobic causing an arrangement called ‘base stacking’
Adenine always forms __ hydrogen bonds with thymine while guanine always forms __ hydrogen bonds with cytosine
2, 3
Chargaff’s Rule
the amount of adenine equals the amount of thymine , and the amount of guanine equals the amount of cytosine, and the total amount of purines equals the total amount of pyrimidine
phosphodiester bond
in a polynucleotide, this is the bond between the 3’’ hydroxyl of a sugar group in a nucleotide and a phosphate group attached to the 5’ carbon of another sugar group
glycosidic bond
in DNA, refers to the nitrogen carbon linkage between the 9’ nitrogen of purine bases or 1’ nitrogen of pyrimidine bases and the 1’ carbon of the sugar group
enzymes in purine synthesis
Glutamine:phosphoribosyl pyrophosphate amidotransferase
enzymes in pyrimidine synthesis
oroate phosphoribosyltransferase
melting temp of DNA
the temperature at which half of the DNA strands are in the random coil or single-stranded (ssDNA) state
B form of DNA double helix
most common form
- “Watson-crick” helix
A form of DNA double helix
which is shorter and wider than the B form with the bases at an angle rather than perpendicular to the helix axis. (RNA double helices and in RNA-DNA hybrid helices, structures observed in transcription and RNA processing)
z form of DNA double helix
Z DNA is left-handed and the backbone is zigzagged, accounting for the name “Z DNA.” (Alzheimer’s disease and Systemic lupus erythematosus
B form
A form
Z form
what presence of grooves allows what
allows access to the hydrogen bonding capabilities of the exposed bases
what does hydrogen bonding capability do
this provides means of sequence-specific interactions
what happens since glycosidic bonds aren’t diametrically opposite of each other
a major groove and minor groove side is fomred
intercalating agent names
Ethidium bromide,
Acridine orange,
Actinomycin D
what do intercalating agents do
- hydrophobic molecules containing flat aromatic and fused
heterocyclic rings can insert between the stacked base pairs of DNA. - potential cancer-reducing reagents
