Biology  5/e   Raven/Johnson
	Student   Online Learning Center

DNA: DNA is a double helix of linked nucleotides. The nucleotide sequences of DNA code for specific amino acid sequences of polypeptides essential for the cell's function. The sum of all of these codes makes up the heredity information of the cell.

Chromosomes: Chromosomes are packages of DNA and protein containing the cell's heredity information.

Nuclear membrane: The nuclear membrane (sometimes called nuclear envelope) contains the nucleus and consists of two membranes penetrated by pores. The outer membrane is continuous with the ER. The pores are dispersed over the surface of the nuclear membrane and form where the outer and inner membranes pinch together.

Microtubules: Microtubules are hollow tubes, about 25 nm in diameter, composed of a ring of 13 protein protofilaments, arranged side by side, around a central core giving them a characteristic tubular shape

Copyright ©1998 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use and Privacy Policy.
McGraw-Hill Higher Education is one of the many fine businesses of The McGraw-Hill Companies.
For further information about this site contact mhhe_webmaster@mcgraw-hill.com.