Lecture 2: NUCLEIC ACIDS Flashcards
(21 cards)
Chemical repositories of genetic information and located inside the ___________ (for eukaryotes) or in the ____________ (for prokaryotes
Nucleic acids nucleus; nucleoid region
Nucleic acids are of _______________ nucleotides linked together by _______________.
biopolymers; phosphodiester bonds
Main difference between NUCLEOTIDES and
NUCLEOSIDES?
A nucleoside consists of a nitrogenous base (either a purine or pyrimidine) attached to a sugar molecule (ribose in RNA or deoxyribose in DNA).
A nucleotide is a nucleoside with one or more phosphate groups attached to the sugar.
What is in a Nucleotide Structure?
purine or pyrimidine base + pentose + phosphate group
Pentoses in Nucleotides
β-D-2’-deoxyribose (in DNA)
β-D-ribose (in RNA)
What are the Nitrogenous bases?
Purine: A / G
Pyrimidine: C / T (DNA) / Uracil (RNA)
These are:
- Flat aromatic rings
- Basic
- Have conjugated double bonds
- Have multiple sites for hydrogen bonding
Nitrogenous Bases
Purines
- Adenine (A) : 6- aminopurine
- Guanine (G) : 2-amino-6 oxypurine
Pyrimidines
- Cytosine (C) : 2-oxy-4-aminopyrimidine
- Thymine (T) : 2,4-dioxy-5 - methylpyrimidine (or 5-methyluracil)
- Uracil (U) : 2,4-dioxy-pyrimidine
What is Tautomeric Shift in Bases? It is also called as ___________?
- Rapid interconversion of isomeric forms
- amino-imino forms of cytosine
- keto-enol forms of guanine
Tautomerization
Tautomeric forms of bases can result to ____________.
anomalous base pairing
Anomalous base-pairing arrangements
Thymine
Guanine
Cytosine
Adenine
Thymine- enol
Guanine- keto
Cytosine- imino
Adenine- amino
Formation of Nucleotides
Two moles of water are liberated upon formation of a nucleotide
Linkages in Nucleotides
Phosphoester bond; β-N-glycosidic bond
Nucleosides
Sugar + base only
How Nucleotides are being named? Cite Example
Nucleoside + phosphate
Sugar: 2’-deoxyribose
Base: adenine
2’-deoxyadenosine-5’-monophosphate (dAMP) a 2’-deoxyribonucleotide
Cite another example for naming nucleotides
Nucleoside + phosphate
Sugar: ribose
Base: cytosine
cytidine-5’-diphosphate (CDP) a ribonucleotide
This form the backbone of the polynucleotide
together with the pentose
Phosphate groups
Phosphate Groups imparts _______ charge to DNA. And Enables DNA to associate with the
_________ charged histones.
Negative ( - ) ; positively ( + )
Primary Structure of DNA: Incoming dNTP is attacked at the ___________ by the ___________ of the growing DNA chain.
a- phosphate ; 3 hydroxyl
By convention, the base sequence is read from the __________ direction.
5’ to 3’ direction
