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