Genetics Northern California


GalactosemiaA disorder that occurs when the body lacks an enzyme needed to process galactose, or milk sugar. When the enzyme is missing, galactose builds up in the body and causes damage to the brain, liver, eyes, and kidneys. Newborns with untreated galactosemia can die within the first few weeks of life. Galactosemia is treated with a galactose-restricted diet. For infants, this means the use of a soy formula. Early detection and prompt dietary treatment can decrease the problems associated with galactosemia.

Ovum or female egg cell or male sperm. Germ cell.


Units of heredity which control growth, development and function of organisms. Located on chromosomes, genes carry information from one generation to the next. A gene is comprised of a continuous sequence of DNA necessary to encode a functional protein. Our body has about 25,000 to 30,000 genes, each of which contains the code for a specific product, typically, a protein such as an enzyme.

Gene expression

The process by which the information encoded in a gene is converted into protein or some form of RNA. The DNA sequence is first transcribed into RNA and then usually, but not always, translated into protein.

Gene family

Group of closely related genes that make similar products. 

Gene mapping

The ordering of genes on chromosomes according to recombination frequency.

Gene pool

The total of all genes in a population.

Gene therapy

Treating disease by replacing, manipulating, or supplementing nonfunctional genes.

Genetic code

The instructions in a gene that tell the cell how to make a specific protein. A, T, G, and C are the "letters" of the DNA code which stand for the chemicals adenine, thymine, guanine, and cytosine, respectively. The code combines the four chemicals in various ways to spell out 3-letter "words" that specify which amino acid is needed at every step in making a specific protein.

Genetic counseling

An educational counseling process for individuals and families who either have a genetic disease, who are at risk to develop such disease, and/or who are at risk to have a baby with a genetic disease. Genetic counseling provides patients with information about their condition and helps them make informed decisions.

Genetic counselor

Health professionals with specialized education, training, and experience in medical genetics and counseling.

Genetic screening

Testing a population group to identify a subset of individuals at high risk for having or transmitting a specific genetic disorder


Referring to clinical geneticist. An individual with an MD and/or PhD degree with specialized training in diagnosing genetic conditions.


The study of heredity and inheritance of traits.


All the genetic material in the chromosomes of a particular organism.


The actual genes carried by an individual (distinct from phenotype).

Germ cell

Ovum or female egg cell or male sperm. Gamete

GestationSynonymous with pregnancy.
Gestational diabetesCarbohydrate intolerance in a woman during pregnancy, usually resolving after delivery. In general, it does not appear to increase the risk of birth defects in the fetus, except when insulin is used in the 3rd trimester, or when oral hypoglycemic agents are used.
Gonadal mosaicism

Also referred to as germline mosaicism, meaning an individual may carry two or more genetically different types of germline cells.