Genetics Northern California



Any chromosome found in the cell nucleus other than the sex chromosomes. Humans typically have 22 pairs.

Balanced translocationA translocation occurs when two or more different chromosomes exchange pieces. It is said to be balanced when no material is either lost or gained during the exchange, and all the genes that make up the exchanged material are still functional.
Chromosome(s)Structures found in the nucleus of a cell which contain the genes. Chromosomes occur in pairs and a normal human cell contains 46 chromosomes, 22 pairs of autosomes and two sex chromosomes.

Having a full set of genetic material consisting of paired chromosomes with one chromosome from each parent. In humans, the diploid chromosome number is 46.

FISH (fluorescence in situ hybridization)

A molecular cytogenetic technique in which labeled probes are hybridized with chromosomes and visualized under a fluorescence microscope. Can detect microdeletion syndromes, trisomies and other genetic conditions.


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 mapping

The ordering of genes on chromosomes according to recombination frequency.


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

HaploidA single set of chromosomes (half the full set of genetic material) present in the egg and sperm cells. Human beings have 23 chromosomes in their reproductive cells. All other cells are diploid.
Human genome project

A large international project to map and sequence all the DNA in human chromosomes.

KaryotypeA microscopic image of an individual's chromosomes arranged in a standard format showing the number, size, and shape of each chromosome.

The ordering of genes on chromosomes according to recombination frequency.

Philadelphia chromosome

A structural abnormality of chromosome 22 typically occurring in a proportion of bone marrow cells in patients with CML (chronic myelogenous leukemia) whereby a reciprocal translocation occurs between chromosomes 9 and 22.


Any multiple of the basic haploid (n=23 chromosomes) other than 2n which is referred to as diploid (ie. 3n, 4n.

Reciprocal translocationThe transfer or exchange of part of two different chromosomes to each other. (ie. Long arm of chromosome # 8 and #10 switch places)
Robertsonian translocation

A rearrangement of chromosomes where the long arms of the chromosomes are fused together and the short arms are lost.

Sex chromosomesChromosomes responsible for sex determination. In humans it is XX in female and XY in males.