Chapter 8 pt 2 Flashcards
Some Bases of DNA Are ______________
Methylated
____________ & ____________ e are methylated more often
Adenine and cytosine
_____________ Carry Chemical Energy in Cells
Nucleotides
________________ are Components of Many Enzyme Cofactors
Adenine Nucleotides
________________ (cyclic AMP, or cAMP), formed from ATP in a reaction catalyzed by adenylyl cyclase, an enzyme associated with the inner face of the plasma membrane.
Adenosine 3′,5′-cyclic monophosphate
Cytosine pKa at N3 is
4.5
Thymine pKa at N3 is
9.5
Molecules are neutral molecules at pH 7
but can undergo ______________ from keto to enol form Lactam» lactim > double lactim
tautomerism
Adenine pKa at N1 is
3.8
Guanine pKa at N7 is
2.4
______________ Bond attaches the pentose ring to a nucleobase to form a nucleoside
Beta-N-Glycosidic
Anomeric carbon in _______________ is bonded to N1 or N-9 of base
B configuration (stable toward hydrolysis but cleavage is catalyzed
by acid
– Nearly free rotation around glycosidic bond in
free nucleotides
– Anti conformation is found in normal B-DNA)
Nucleotides are ________ & ________
nucleoside + one or more phosphates (have many cellular roles)
What are the best known nucleotides?
ADP & ATP
Nucleotide deriviate
ADP-Glucose
5-Methylcytosine
common in eukaryotes and found in bacteria
N6-Methyladenosine
is common in bacteria but not in eukaryotes
Epigenetic markers
Differentiate self DNA from
foreign DNA (prokaryotes) or
active genes (eukaryotes)
Epigenetic markers (Minor Nucleosides in DNA: Modification after DNA synthesis)
Differentiate self DNA from
foreign DNA (prokaryotes) or
active genes (eukaryotes) (Environmental conditions affect
gene activation/ deactivation
* Pattern can be inheritable)
Inosine (Minor Nucleosides in RNA)
May occur in the “wobble position” of anticodons in tRNA (De-aminated adenosine; Provides richer genetic code)
Pseudouridine
Found widely in tRNA and rRNA of eukaryotes Made
from uridine by enzymatic isomerization after RNA synthesis
Deamination
100 C U events /day in a mammalian celL
Depurination
10,000 purines lost/day in a mammalian cel
________________, Chemical Mutagenesis, and Radiation Damage of DNA causes aging (No detail discussed)
Accumulated Oxidative
______________ Hydroxylguanine especially in mitochondrial DNA
Oxidative damage
_______________ Methylation of guanine
Chemical alkylation
_____________ induces dimerization of pyrimidines; this may be the main
mechanism for skin cancers.
UV light
_______________ (X-rays and -rays) causes ring opening and strand
breaking which must be repair by complex recombinatio
Ionizing radiation
Nucleic Acid Structure: Polynucleotides are nucleotide “residues” linked by _________________
phosphodiester (3’ –OH of nucleotide-1 linked to 5’ P of
nucleotide-2)
_____________ RNA Hydrolysis under alkaline conditions
Base-catalyzed
______________ Carries the code for the Amino Acid Sequence of Proteins
Messenger RNA
DNA template —–> mRNA —–> single stranded with ribose instead of
deoxyribose and uracil instead of __________
thymine (One mRNA may code for more than one protein
* Transfer RNA (tRNA) transfers genetic information from DNA to
proteins tRNA codon specifies a specific am)
