The Nucleus in the Cell
The nucleus contains the cell's genetic information
- in other words, the DNA. The DNA in eukaryotes is
found in several pieces.
Each piece is associated with
various proteins and is called a chromosome. So when
we talk about chromosomes, we're really just talking
about the pieces of DNA in the nucleus of a cell.
Notice that we specified eukaryotes. Prokaryotes have
DNA too, even though they don't have a nucleus. Their
DNA is found as one large circular chromosome floating
around in the cytoplasm. The DNA is still a double helix;
the double helix is just joined at both ends to make
Even though all chromosomes contain DNA, it is not
true that all chromosomes are identical. The nucleotide
base sequences in two different pieces of DNA - two
different chromosomes - can be (and are) different.