List the characteristics of DNA molecules.
Characteristics of DNA molecule: The two chains are spirally coiled about around a common axis to form a regular, right-handed double helix. The double helix has a major groove and minor groove alternately. The helix is 20Å wide; it’s one complete turn is 34Å long, and has 10 base pairs, and the successive base pairs are 3.4Å apart. The two chains are complementary to each other with respect to base sequence. The two strands are hydrogen-bonded: A on one chain is joined to T on the other chain by 2 hydrogen bonds; C on one chain is linked to G on the other chain by 3 hydrogen bonds. The two strands run in an antiparallel direction. The amount of A + G = the amount of T + C; the amount of A = the amount of T: the amount of G = the amount of C. Sugar and phosphate groups occur in equal proportion. The DNA molecule is remarkably stable due to hydrogen bonding and hydrophobic interactions. The DNA molecule undergoes denaturation and renaturation easily. The denatured DNA strands are hyperchromic. The DNA molecule can replicate and repair itself, and can also transcribe RNAs. The base sequence of one chain serves as the genetic code. The DNA can function in vitro. The amount of DNA per nucleus is constant in all the body cells of a given species.
