Chromosomes
Chromosomes...
- are comprised primarily of DNA in
association with various proteins and RNA
- are located in the nucleus
- are not usually visible in non-dividing cells but condense into
visible structures as the cell prepares to
divide
- occur in pairs, one member derived from the female parent and
the other from the male parent; members of a chromosome pair are
called homologs
- number 46 in humans, with 22 pairs of autosomes and a
pair of sex chromosomes (2 X's in females; an X and a
partially homologous Y in males)
- in cells that contain pairs of homologous chromosomes are
designated as diploid cells and the 46 chromosomes are
referred to as 2n; in gametic cells—eggs (females) and
sperm (males)—there is only one copy of each chromosome, and these
cells are referred to as haploid with n number
of chromosomes (n = 23 in humans)
- have a specialized region called the centromere to
which fibers attach during cell division. The location
of the centromere gives a chromosome its characteristic shape
- may be stained to bring out distinctive features that allow the identification of each chromosome.
Related Information
Last updated Thursday, February 22, 2001.
© 2001 by PRR, Inc. All rights reserved.