The Inheritance of Retinal Degenerations


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autosomal dominant
a trait (or a disease) that is produced when only one copy of a gene is present

autosomal recessive
a trait (or a disease) that is produced only when two copies of a gene are present

one of the non-sex chromosomes; there are 22 pairs of autosomes

an individual with one mutated gene paired with one normal gene; a carrier of a gene for a recessive disease does not have the disease

carrier detection
using tests to determine who carries a mutated gene for a recessive disease

the smallest unit of living matter; the human body is made up of about 10 trillion cells

the layer of the eye behind the retina that contains major blood vessels

a microscopic, rod-like structure in the cell's nucleus that carries genetic material

the union of an egg and a sperm that forms a cell capable of surviving and maturing, which results in pregnancy

present at birth

deoxyribonucleic acid, the molecule that holds genetic information; it is the biochemical molecule that makes chromosomes and genes

a protein involved in an important biochemical reaction in the body; a defective enzyme can be the result of a mutated gene

family history
information about an individual's family concerning its medical background and usually concentrating on the history of disease, birth defects and reproduction

a unit of heredity; composed of deoxyribonucleic acid (DNA)

gene therapy
the administration of genetic material into cells of a patient to correct or replace a specific gene that is not working properly

the science concerning genes and heredity

genetic counselor
a professional trained to evaluate a family's medical history to determine the presence of genetic diseases or other inherited traits and to assess the risk of these occurring in other family members

inheritance pattern
the way in which a gene or trait is passed through generations of a family

passed through generations of a family, from parents to children

occurring in only one individual in a family

two or more markers that are close enough together on a chromosome to be inherited together

the central area of the retina

a gene or DNA fragment with a known location on a chromosome that is associated with a certain disease; it can be used as a point of reference when looking for disease-causing mutations

medical geneticist
a medical doctor who specializes in the diagnosis and treatment of inherited diseases

a change in a gene


concerning the nervous system

night blindness
inability to see at night or in areas with low lighting

a structure within the cell containing genetic material

a medical doctor who specializes in the diagnosis and treatment of eye diseases

a multigenerational family tree using symbols to denote lineage and genetic information


prenatal diagnosis
the diagnosis of a disease in an unborn baby

presymptomatic diagnosis
the diagnosis of a disease before the onset of clinical symptoms

the layers of cells in the back of the eye that are responsible for sensing light and transmitting light- induced signals to the brain

reduced penetrance
when the effect of a mutated gene for a dominant disease is somehow modified or reduced and does not always cause disease when present

sex chromosome
an X or Y chromosome; the Xx pair determines female and the XY pair determines male

a distinguishing characteristic

not having the disease

variable expressivity
when the effect of a mutated gene for a dominant disease may be severe in one member of the family and mild in another

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Date last modified December 4, 1998