What does kilobase mean?
A kilobase is a standard unit for describing the length of a nucleic-acid sequence. It equals 1,000 nucleotide bases, although in measurements of double-stranded DNA it generally refers to 1,000 base pairs, with each pair containing two complementary bases. The term is widely used in genetics, genomics, molecular biology, and biotechnology to describe the size of genes, DNA fragments, chromosomes, and complete genomes. For example, a gene might be said to be 2.5 kilobases long, while a genome might contain several million kilobases. The related unit “kilobase pair,” abbreviated kbp, is often used when the distinction between individual bases and paired bases needs to be explicit. Although kilobase and kilobit are sometimes abbreviated similarly as kb, they measure fundamentally different things: a kilobase concerns molecular sequences, while a kilobit concerns digital information.
nounA unit of nucleic-acid length equal to 1,000 nucleotide bases. In measurements of double-stranded DNA, a kilobase usually represents 1,000 base pairs.
- A unit of nucleic-acid length equal to 1,000 nucleotide bases, commonly used to describe the physical size of a DNA or RNA sequence.
"The researchers sequenced a region spanning nearly ten kilobases of human DNA."
"The deletion covered approximately 1.5 kilobases near the end of chromosome 7."
"Each viral genome is several kilobases long and contains a small number of genes."
The plural takes the ordinary English suffix -es, without an apostrophe.
"The two bacterial genes are separated by several kilobases."
A kilobase is DNA's ruler: one short step represents 1,000 nucleotide building blocks.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of kilobase
Kilobase combines the metric prefix kilo-, ultimately from Greek kiliā, “thousand,” with base, the term for a nucleotide building block. The word base comes through French from Latin basis, “foundation,” and ultimately from Greek basis, “step” or “foundation,” in a semantic development unrelated to alkaline chemistry. Kilobase entered use as a scientific unit for expressing the length of nucleic-acid sequences.
How kilobase is actually used
The abbreviation is commonly written as kb, while kb sometimes also means kilobit, so the biological context should be clear. The plural is kilobases.
Easily confused with kilobase
A kilobase measures the number of nucleotide units in a nucleic-acid sequence, whereas a kilobit measures 1,000 bits of digital data.