Scientists have decoded the genetic make-up of the rhesus macaque, an Old World monkey.
Macaques diverged from our ancestors 25 million years ago
It is the third primate (after humans and chimps) to have the secrets of its DNA laid bare.
The work, led by the Baylor College of Medicine in Houston, Texas, is reported in the journal Science.
Researchers say the information will help them understand better the evolutionary relationships between humans and their closest relatives.
It will also have major implications for the study of human health and disease.
Macaques are used worldwide as laboratory "models" to study medical conditions as diverse as HIV and heart disease.
The international team behind the sequencing effort incorporates more than 170 scientists from 35 institutions.
They say in their analysis that the rhesus macaque, chimp and humans share about 97.5% of the same genes.
Macaques are used to study heart disease and HIV
The researchers identified about 200 genes that show evidence of positive selection during evolution, making them potential candidates for determining the differences among primate species.
These genes are said to be involved in hair formation, immune response, membrane proteins and sperm-egg fusion.
Also, the geneticists found some instances where the normal form of the macaque protein looks like the diseased human protein.
One example found is phenylketonuria (PKU) which can lead to brain damage and mental retardation because the human lacks an important enzyme.
The research indicates macaques diverged from our ancestors 25 million years ago.