The Inheritance of Retinal Degenerations

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

autosome

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

carrier

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

cell

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

choroid

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

chromosome

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

conception

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

congenital

present at birth

DNA

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

enzyme

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

gene

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

genetics

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

inherited

passed through generations of a family, from parents to children

isolated

occurring in only one individual in a family

linked

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

macula

the central area of the retina

marker

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

mutation

a change in a gene

myopia

nearsightedness

neurologic

concerning the nervous system

night blindness

inability to see at night or in areas with low lighting

nucleus

a structure within the cell containing genetic material

ophthalmologist

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

pedigree

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

peripheral

side

prenatal diagnosis

the diagnosis of a disease in an unborn baby

presymptomatic diagnosis

the diagnosis of a disease before the onset of clinical symptoms

retina

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

trait

a distinguishing characteristic

unaffected

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

Date last modified December 4, 1998