Glossary of Genetic Terminology
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G BANDS:
Banding patterns on chromosomes make it easier
to examine the chromosomes under the microscope for abnormalities in structure
and number. G bands are one type of banding pattern, induced to appear on
chromosomes by staining them with a special chemical called Giemsa.
GAMETE:
Refers to the sperm cells in males and the egg cells in females.
GENE:
The basic unit of heredity; a segment of DNA which contains the information for a specific characteristic or function.
GENE CLONING:
Isolating a gene and then making multiple copies of
it by inserting it into a bacterial cell or another
organism.
GENE MAPPING:
Determining the relative locations of different genes on chromosomes.
GENE THERAPY:
Treating genetic conditions and diseases by replacing, manipulating or supplementing genes that are not working properly (see Genetics Fact Sheet 27).
GENETIC CARRIER:
Please see 'Carrier of a mutated gene'.
GENETIC CODE:
The information contained in the DNA which is 'interpreted' by the cells to produce
proteins. The chemicals (nucleotides) which
make up the DNA can be described by the letters A (Adenine), T (Thymine), C
(Cytosine) and G (Guanine). Thus the genetic code can be written as a series of
letters (for example AAA CGT TTC).
GENETIC CONDITION:
A genetic condition is caused by a change in the genetic information. Genetic conditions may be caused by a mutation in a single gene or may be caused by a change in chromosome structure or number (see Genetics Fact Sheet 2).
GENETIC COUNSELLING:
The provision of diagnosis, information and support by health professionals with specialised training in genetics and counselling (see Genetics Fact Sheet 3).
GENETIC COUNSELLOR:
A health professional with specialised training in genetics and counselling who
can provide information and support to individuals or families with concerns
about a genetic condition which may run in their family.
GENETIC ENGINEERING:
Laboratory techniques used to alter or manipulate the genetic make-up of cells
or an organism by deliberately removing, changing or inserting individual genes.
GENETIC HETEROGENEITY:
Different mutations in a gene causing the same condition.
GENETIC MAPPING:
Determination of the relative positions of genes on a chromosome and a measure of the distance between them.
GENETIC PREDISPOSITION:
Having some genetic factor(s) that may make an individual more likely to develop a particular condition than the general population.
Analysis of an individual's genetic make-up to determine predisposition to a particular health condition or to confirm a diagnosis of a genetic condition. Other applications for genetic testing include forensic DNA analysis (used in criminal investigations) and paternity testing (to determine the father of an individual) (see Genetics Fact Sheets 21 and 22).
The study of genes and inheritance patterns.
GENOME:
The complete set of genes carried by an individual or a cell.
Please see 'Imprinting' (see Genetics Fact Sheets 14 and 15).
The genetic constitution of an individual
GERM CELLS:
The cells of the body that are used in reproduction (egg and sperm).
GERMLINE:
The family of cells that divide to produce new germ cells.
GERMLINE MOSAICISM:
When the germ cells (sperm or egg cells) have a different genetic make-up to the cells in the rest of the body.
A heritable change in the DNA that occurred in a germ cell (a cell destined to become an egg or in the sperm).
GONADAL MOSAICISM:
Please see 'germline mosaicism'.
One of the four basic building blocks (nucleotide bases) that makes up the genetic code (DNA). It is represented by the letter G.