What is the difference bewteen a gene and a chromosone?

Question

. . . And the difference between a phenotype and a karyotype?

Answer 1

A gene is section of the DNA that makes up a chromosome - sort of how a link is one section of a chain. Many, many genes make up a single chromosome.

Phenotype tells the characteristic or behavior that is caused by a gene. It's the form of a trait that an individual has. Examples of phenotypes are: tall, green, wingless, blue eyes, ...

A karyotype is a picture of an individual's chromosomes, all lined up in order from longest to shortest, and paired with their homologous partners. See pictures of karyotypes here:
http://www.altavista.com/image/results?itag=ody&q=karyotype&mik=photo&mik=graphic&mip=all&mis=all&miwxh=all

Answer 2

Chromosones are large structures in cell nuclei, containing DNA. Genes are segments of DNA that describe inheritable traits.