Genetic and Medical Glossary

absence of fine and sharp appearance of brows, nose, lips, mouth and chin, usually because of rounded and heavy features or thickened skin with or without thickening of subcutaneous and bony tissues

absence of concavity or convexity of the face when viewed in profile

term used to describe a delay in a child's growth or development; usually applied to children up to two years of age whose growth is below the 3rd or 5th percentiles for their age

a gene that does not function properly

autosomal dominant disorder characterized by microcephaly, distal limb malformations (eg, short middle phalanges of the 2nd and 5th fingers), and esophageal/duodenal atresia; usually associated with learning disabilities are common

gradual reduction in girth of the digit from proximal to distal

soft tissue continuity in the A/P axis between two fingers that lies significantly distal to the flexion crease that overlies the metacarpophalangeal joint of the adjacent fingers

abnormal or surgically made passage between a hollow or tubular organ and the body surface, or between two hollow or tubular organs

a form of molecular cytogenetics; an extremely sensitive assay for determining the presence of deletions on chromosomes, which uses a fluorescence-tagged segment of DNA that binds to the DNA region being studied

congenital abnormality where the neurons in an area of the brain failed to migrate in the proper formation in utero; malformation of cortical development, which is the most common cause of medically refractory epilepsy in the pediatric population

“soft spot” on the skull that remains open for the brain to develop and closes during infancy

reduced genetic diversity that results when a population is descended from a small number of colonizing ancestors

small break or constriction of a chromosome that can be visualized after special treatment of the chromosomes (in individuals affected with Fragile X syndrome, a fragile site can often be seen on their X chromosome)

chromosomal disorder caused by mutations in the FMR1 gene on the X chromosome, resulting in an increased number of copies of a portion of the gene called CGG repeats; the greater the number of copies of CGG, the more likely there will be increased severity of the disorder; disorder occurs mostly in males and is characterized by moderate intellectual disability, motor and language delays, and autistic behaviors; facial features include large head, long face, prominent forehead and chin, and protruding ears

a DNA mutation involving the insertion or deletion of one of several nucleotides that are not in multiples of three, resulting in a shift of the codon reading frame; usually produces nonfunctional proteins. Normally, the cell reads a gene in groups of three bases. Each group of three bases corresponds to one of 20 different amino acids used to build a protein. If a mutation disrupts this reading frame, then the entire DNA sequence following the mutation will be read incorrectly

bilateral bulging of the lateral frontal bone prominences with relative sparing of the midline