ASAM NUKLEAT
Oleh :DR. Ir. Joni Kusnadi, MSi.
DNA structure.
History:• 1868 Miescher – discovered nuclein
• 1944 Avery – experimental evidence that DNA is constituent of genes.
• 1953 Watson&Crick – double helical nature of DNA.
• 1980 X-ray structure of more than a full turn of B-DNA.
Adapted from Molecular Expression (http://micro.magnet.fsu.edu/cells/plantcell.html)
Adapted from the Merck Manuals On-line Medical Library:
http://www.merck.com/mmhe/sec01/ch001/ch001b.html#sec01-ch001-
ch001b-6
Animal cells develop to specific cell types in different organs
(differentiations). Specific cell types are for specific biological functions
(e.g. production and secretion of specific hormones or enzymes).
Nucleus
Five types of bases.
Nucleotides and phosphodiester bond.
Phosphodiester bond
Complementarity of nucleosides – bases for double stranded helical structure
base: thymine(pyrimidine)
sugar: 2’-deoxyribose
monophosphate
no 2’-hydroxyl
(5’ to 3’)
5’
3’
base:adenine(purine)
1’2’
4’
3’ linkage
5’ linkage
DNA
nucleotides (nucleoside mono-, di-, and triphosphates)
base
sugar
phosphate(s)
base
sugar
nucleoside
DNA: terminology
1. DNA is double stranded2. DNA strands are antiparallel3. G-C pairs have 3 hydrogen bonds4. A-T pairs have 2 hydrogen bonds5. One strand is the complement of the other6. Major and minor grooves present different
surfaces7. Cellular DNA is almost exclusively B-DNA8. B-DNA has ~10.5 bp/turn of the helix
DNA: structure
nucleoside
base
sugar
Base Nucleoside (RNA) Deoxynucleoside (DNA)
Adenine Adenosine Deoxyadenosine
Guanine Guanosine Deoxyguanosine
Cytosine Cytidine Deoxycytidine
Uracil Uridine (not usually found)
Thymine (not usually found) (Deoxy)thymidine
RNA: terminology
1. RNA can be single or double stranded2. G-C pairs have 3 hydrogen bonds3. A-U pairs have 2 hydrogen bonds4. Single-stranded, double-stranded, and loop RNA
present different surfaces
RNA: Structure
Double helical structure of DNA.
A- and B-DNA – right-handed helix, Z-DNA – left-handed helix
B-DNA – fully hydrated DNA in vivo,10 base pairs per turn of helix