Introduction to Nanotechnology

12.3. NUCLEIC ACIDS 321
Figure 12.10. Model of the DNA double helix. The width (2nrn). the spacing beween nucleorides
(0 34 nm), and the lengzh of the repeat unil or pitch (3.4 nm) of the helix are indicaled in the
upper left, The sugar-phasphate backbones. the arrangemenis 01 the nucleotides (C, T, G, A),
and Ihe four cases of nucleotide base pairing are sketched in the lower right. [From Mrlader
(2001), p. 225.1
of proteins. The final condensed shcbre of the metaphe chrommomc, sketched
in Fig. 12. I 1 f, is small enough tu fit inside the nucleus of a cel1.
The genome is thc complete set of hcreditary units callcd genex, each of which is
responsible for a particular structure or function in the body, such as determining the
color of one's eyes. In human beings the genome consists of46 chmmsomcs (two
haploid sets of 23 chromosomes), with an average of about 1600 genes arranged
lengthwise along each chromosome. The human haploid genome contains about
3.4 x IO" base pairs, an average of about 1 SO x IO6 basc pairs pes chromosome.