Genetics Northern California


RecessiveA trait or gene that is expressed in the offspring only when a copy from each parent is impaired.
Reciprocal translocationThe transfer or exchange of part of two different chromosomes to each other. (ie. Long arm of chromosome # 8 and #10 switch places)
Recombinant DNAArtificially created DNA in which a gene or part of a gene from one organism is inserted into the genome of another.
RepeatsA single or multiple nucleotide base(s) (DNA) that are repeated sequentially in a gene. For example, in Fragile X syndrome, there is a trinucleotide repeat, CGG, in the FMR1 gene that is repeated many times. Individuals without Fragile X have < 30 repeats, but affected individuals have >200 repeats.
RFLPRestriction fragment length polymorphism is polymorphism in a DNA sequence that can be detected on the basis of differences in the length of DNA produced after digestion of the DNA with a specific enzyme.
RhAbbreviation for rhesus in Rh factor; Rhesus type is the symbol for a particular antigen (protein) present on the membranes of red blood cells. Commonly used in the terms Rh positive or Rh negative

The chance that a particular outcome will occur. This is usually used to refer to the chance of a particular genetic condition occurring.

Risk factorA clearly defined occurrence or characteristic that has been associated with the increased rate of a subsequently occurring disease; something that increases the chance of a disease occurring (patched together from Dorland's).
Risk factorsThese are factors that can increase the likelihood of elevated cholesterol and coronary artery disease and are as follows: age, gender, overweight, smoker, elevated blood pressure, lack of exercise, and family history of elevated cholesterol (i.e., low HDL or elevated Lp(a) and/or stroke or heart attack prior to age 55.)

Ribonucleic acid, a nucleic acid formed upon a DNA template using ribose instead of deoxyribose.

Robertsonian translocation

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