Genetics Northern California


Base PairA pair of complementary nucleotide bases, as in double-stranded DNA. Used as the unit of measurement of the length of a DNA sequence.
Homeobox gene

A short stretch of nucleotides whose base sequence is virtually identical in all the genes that contain it. Found in many organisms from fruit flies to human beings.

Kilobase (kb)Unit of length for DNA fragments equal to 1000 nucleotides. 
MRNA (messenger ribonucleic acid)

An RNA molecule transcribed from the DNA of a gene, and from which a protein is translated by the action of ribosomes. The basic function of the nucleotide sequence of mRNA is to determine the amino acid sequence in proteins.


Building blocks of DNA or RNA consisting of a base(adenine, guanine, cytosine and thymine)a molecule of sugar and a phosphate group.


A short sequence of single stranded DNA or RNA. It is often used as a probe for detecting complementary DNA or RNA.

RepeatsA single or multiple nucleotide base(s) (DNA) that are repeated sequentially in a gene. For example, in Fragile X syndrome, there is a trinucleotide repeat, CGG, in the FMR1 gene that is repeated many times. Individuals without Fragile X have < 30 repeats, but affected individuals have >200 repeats.
Triplet repeat (trinucleotide repeat)

A pattern where a given set of nucleotides is repeated multiple times ( many times more than in an individual without the condition)which causes a specific disease.