The terms and descriptions provided in this glossary have been completed with the help of several sources:

• National Human Genome Research Institute - Talking Glossary
• Human Genome Project Information
• PhRMA Genomics (no longer online)
• Word Central's Student Dictionary (Merriam Webster)

Sources are listed with the definitions.

MNO

Meiosis

The process of two consecutive cell divisions in the diploid progenitors of sex cells. Meiosis results in four rather than two daughter cells, each with a haploid set of chromosomes.
Source: Human Genome Project Information

Messenger RNA (mRNA)

"Blueprint" for protein synthesis that is transcribed from one strand of the DNA (gene) and which is translated at the ribosome into a polypeptide sequence. Each set of three bases, called codons, specifies a certain protein in the sequence of amino acids that comprise the protein. The sequence of a strand of mRNA is based on the sequence of a complementary strand of DNA. [Talking Glossary]

Microarray technology

A way of studying how large numbers of genes interact with each other and how a cell's regulatory networks control vast batteries of genes simultaneously. The method uses a robot to precisely apply tiny droplets containing functional DNA to glass slides. Researchers then attach fluorescent labels to DNA from the cell they are studying. The labelled probes are allowed to bind to complementary DNA strands on the slides. The slides are put into a scanning microscope that can measure the brightness of each fluorescent dot; brightness reveals how much of a specific DNA fragment is present, an indicator of how active it is. [Talking Glossary]

Microinjection

Injection of tiny amounts of a substance into a microscopic body, such as a single cell.

Mitochondrial DNA

The genetic material of the mitochondria, the organelles that generate energy for the cell. [Talking Glossary]

Mitosis

The process of nuclear division in cells that produces daughter cells that are genetically identical to each other and to the parent cell.
Source: Human Genome Project Information

Molecule

The smallest particle of a substance having all the characteristics of the substance.
Source: Word Central Student's Dictionary

Monogenic disorder

A disorder which is caused by mutations in just one gene (such as haemophilia), as opposed to polygenic disorders (such as hypertension) which involve the interaction of several genes.
Source: PhRMA Genomics

Mutation

A permanent structural alteration in DNA. In most cases, DNA changes either have no effect or cause harm, but occasionally a mutation can improve an organism's chance of surviving and passing the beneficial change on to its descendants. [Talking Glossary]

Mutagenesis

When a chemical or physical agent is used to cause permanent genetic alterations.
Source: Human Genome Project Information

Nuchal translucency test

The nuchal translucency test is used to determine if a woman is at high risk of having a baby with a chromosomal abnormality, such as Down syndrome.

Nucleotide

One of the structural components, or building blocks, of DNA and RNA. A nucleotide consists of a base (one of four chemicals: adenine, thymine, guanine, and cytosine) plus a molecule of sugar and one of phosphoric acid. [Talking Glossary]

Nucleus

The largest, most prominent organelle in eukaryotic cells, the nucleus is a round or oval body that is surrounded by the nuclear envelope and contains the genetic information necessary for control of cell structure and function. It is the central cell structure that houses the chromosomes and is essential to such cell functions as growth, metabolism, and reproduction. [Talking Glossary]

Oncogene

A gene that is capable of causing the transformation of normal cells into cancer cells. [Talking Glossary]

Organelle

A structure in a single-celled living thing that has a special task as an organ does in a many-celled living thing.
Source: Word Central Student's Dictionary

Organism

An individual living thing that carries on the activities of life by means of organs which have separate functions but are dependent on each other : a living person, plant, or animal.
Source: Word Central Student's Dictionary

Osteoblasts

Osteoblasts are one of four types of bone cell. They synthesize most of the bone proteins.