1. Nucleotides, Nucleic Acids, & DNA Flashcards
different “codes”
single letter code for DNA, transcripted to single letter code for RNA, tranlsated to triple letter codon for amino acids (and ultimately proteins)
central dogma
DNA—RNA—> protein
via transcription, then translation
base
fundamental unit of nucleic acid
planar, stack together in a double helix
purines
A, G
larger
pyrimidines
C, U, T
smaller
nucleoside
based attached to a ribose sugar
nucleotide
nucleoside attached to a phosphate
adenine example
adenine= base
adenosine=nucleoside
adenylate=nucleotide
ribose
aldose, exists in cyclic form
attaches molecules via 5’ hydroxyl
DNA v. RNA
DNA: H at position 2, thymine
RNA: OH at position 2, uracil
DNA is aways written
5’ to 3’
if not labeled on exam, assume 5’ to 3’
AT v. GC linkages
AT: 2 H bonds
GC: 3 H bonds
How many base pairs per turn in DNA double helix?
10.5
bases hydrogen bond on the interior, phosphate bonds on the outside
DNA complementarity
allows each strand to serve as a template during replication
DNA undergoes?
HEMIconservative replication
each new strand produced consists of 1 parent strand & 1 daughter strand
forms of DNA?
A form: right handed double helix w/11 bp turns
B form: MOST COMMON, right handed double helix w/10.5 bp turns
Z form: least common, left-handed double helix with 12 bp turns
palindrome
2 sequences that are identical when read 5’ to 3’
mirror repeat
symmetry occurs on the same strand
DNA secondary structure: hairpin
formed from a palindrome sequence, with each base binding with its complement on the other side of the palindrome
RNA structure
single stranded (can be double stranded) double stranded RNA is more stable than double stranded DNA more relaxed helix than DNA can form hairpins, secondary structure is protein-like
complementarity (2 things)
- aspect for both double stranded DNA & double stranded RNA
2. basis for anti-parallel stability in the nucleic acid
what stabilizes nucleic acids?
weak, non-covalent bonds & the exclusion of water
what destabilizes nucleic acids?
heat & salt
melting (denaturing) curve for nucleic acids
melting temperature (Tm) = temperature at which 50% of the strands are separated
as melting temp goes up, GC content goes up
“DNA” breathing
in AT rich regions of DNA, we observe transient strand separation occurring even at physiological temperatures
