Genetic and Medical Glossary


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There are currently 22 names in this directory beginning with the letter B.
Balanced translocation
rearrangement of the chromosomes with no apparent loss or gain of chromosomal material; hence, a person with this rearrangement is not affected in any way; reciprocal translocation

Bannayan–Riley–Ruvalcaba syndrome
genetic condition characterized by a large head size (macrocephaly), multiple noncancerous tumors and tumor-like growths called hamartomas, and dark freckles on the penis in males; many have intellectual disability or delayed development, particularly the development of speech and of motor skills

Base pair (bp)
measure of the size of a DNA fragment or the distance along a DNA molecule between markers

Bechçet syndrome
disorder that causes inflammation in blood vessels throughout the body, leading to mouth sores, eye inflammation, skin rashes and lesions, and genital sores; may have an autoimmune basis

Beckwith-Wiedemann syndrome
overgrowth disorder caused by paternal duplications (imprinting) of 11p15.5 on chromosome 11; characterized by above-average birth weight and increased growth after birth, an usually large tongue (macroglossia), enlargement of certain internal organs (visceromegaly), and protrusion of a portion of the intestines and abdominal organs through a tear in the wall of the stomach or bellybutton (abdominal wall defects)

refers to a uterus that is divided into two parts, usually separate at the upper end and joined at the lower end

Bicuspid aortic valve
aortic valve in the heart that has two flaps (cusps) that open and close, instead of the three flaps of a normal heart

Bifid uterus
an abnormal uterus that may be either a single or a double organ with two horns, or branches

Bifid uvula
bifurcation of the uvula, an incomplete form of cleft palate

Biliary atresia
condition in which the bile ducts inside or outside the liver do not develop normally, causing bile that normally flows from the liver to the gallbladder to be blocked, which can lead to liver damage and cirrhosis

Bipolar disorder
a mental disorder marked by alternating periods of elation and depression

Blackfan–Diamond syndrome
blood disorder, characterized by a failure of the bone marrow (the center of the bone where blood cells are made) to produce red blood cells

Blaschko’s lines
pattern of distribution of skin lesions or pigmentary anomalies, linear on the extremities, S-shaped curves on the abdomen, and V-shaped on the back; thought to result from genetic mosaicism and interplay of transverse clonal proliferation and longitudinal growth and flexion of the embryo

lax, wrinkled, and baggy eyelid skin

fixed reduction in the vertical distance between the upper and lower eyelids with short palpebral fissures; often associated with epicanthus inversus

cephalic index (ratio of head width expressed as a percentage of head length) greater than 81%; shortened antero-posterior dimension (length) of the head compared to width

Brachydactyly of the hand
angulation of a digit toward the anterior axis (radial

short distance from the end of the finger to the most distal interphalangeal crease or DIPJ flexion point (ie, short fingers)

central trunk of the brain, consisting of the medulla oblongata, pons, and midbrain, and continuing downward to form the spinal cord

Branchial fistula
congenital epithelial cyst that arises on the lateral part of the neck due to failure of obliteration of the second branchial cleft in embryonic development

Branchio–oculo–facial syndrome
autosomal dominant genetic disorder characterized by the proliferation of blood vessels (hemangiomatous) in the lower neck or upper chest, low birth weight, retarded growth and degrees of intellectual impairment; patients may have a pseudo cleft of the upper lip resembling a poorly repaired cleft lip, a malformed nose with a broad bridge and flattened tip, blockage of the tear ducts, malformed ears, lumps in the area of the neck or collarbone and/or linear skin lesions behind the ears

Buschke–Ollendorf syndrome
hereditary disorder of connective tissue characterized by benign, connective tissue nevi (hamartomas) in the skin, and the formation of small, round spots of increased bone density (osteopoikilosis)

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