Genes

Prokaryotes

-Prokaryotes do not have a nucleus

-DNA is found in the cytoplasm as a circular DNA (plasmids)

-prokaryote DNA not associated with Histones

Eukaryotes

-Eukaryotic cells have a true nucleus

-Eukaryotic DNA is long, linear and associated with histone proteins

Mitochondria contain prokaryotic like DNA: short circular no histones

Gene

-base sequence of DNA

this code for either:

• the amino acid sequence of a polypeptide

• a functional RNA (tRNA and rRNA)

A gene occupies a fixed position called a locus. e.g. the BRCA1 gene is located on chromosome 17

Triplet-a sequence of a three base code

these codes are degenerate and therefore more than one codon codes for an amino acid

Intron-Non coding region of a gene

Exon-Coding region