DNA structure

DNA is the chemical that makes up the genetic material in a cell nucleus. In the nucleus, DNA is contained in structures called chromosomes.

A DNA molecule consists of two long strands that twist around each other to form a double helix. Each strand is a chain of repeating units called nucleotides. A long molecule made from repeating units is called a polymer, so DNA is a polymer.

Genes

A gene is a small section of DNA on a chromosome. The DNA in a gene contains a sequence of bases. The order of these bases provides the information for the order in which amino acids are joined.

Amino acids are the building blocks of proteins. When they are joined in the order specified by a gene, they form a specific protein. Different base sequences can specify different amino acid sequences, producing different proteins.

Human genome research in medicine

An organism’s genome is all of its genetic material. In humans, it includes genes as well as DNA that does not form part of genes. A gene is a section of DNA that contains information for making a functional product, often a protein.

The human genome has been studied as a whole. This provides a basis for investigating whether particular versions of genes are linked to particular diseases. Researchers can compare genetic information from people with and without a disease to look for such links. A link alone does not prove that a gene causes the disease, so further investigation is needed.

Identifying a gene linked to an inherited disorder can help explain how the disorder arises. For example, an inherited change in a gene may alter the protein it produces, affecting how cells function. Understanding this connection can help researchers develop treatments that address the effects of the genetic change.

Human genome research and migration

People inherit their DNA from their ancestors. When human populations share genetic similarities, those similarities can provide evidence that they share ancestors. Researchers compare genetic patterns across populations to investigate how closely their histories are connected.

Using genetic patterns to infer migration

When groups from a population move to different places, they carry inherited genetic variants with them. Over many generations, populations may develop different patterns of variants. Researchers can compare patterns across present-day populations to infer which populations share ancestry and how their ancestors may have moved between regions.

For example, if populations in two regions share many inherited variants, this may suggest a connection between their ancestors. Comparing several populations can help researchers build a possible picture of movement between regions.

Genetic similarity alone does not reveal an exact route or prove when a migration happened. Populations may also mix after migrating, so researchers use patterns across many genetic variants rather than relying on a single similarity.