Chromosomal Abnormalities - Vocabulary Review (Video Lecture)

A set of vocabulary flashcards covering key concepts: aneuploidy, euploidy, specific syndromes, and common chromosomal rearrangements and diagnostic concepts from the notes.

Aneuploidy

Abnormal number of chromosomes, not a whole multiple of the haploid set.

Euploidy

A cell with a whole multiple of the haploid chromosome number (e.g., 23, 46, 69). Polyploidy falls under this category.

Monosomy

Loss of one chromosome; autosomal monosomies are usually incompatible with life.

Trisomy

Addition of one chromosome (three copies instead of two); example: Down syndrome (47, +21).

Tetraploidy

Four complete sets of chromosomes (92 total); usually lethal in humans.

Polyploidy

More than two complete sets of chromosomes in a cell.

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate properly during meiosis or mitosis.

Down syndrome (Trisomy 21)

Aneuploidy with three copies of chromosome 21 (47, +21); characterized by intellectual disability and distinctive features.

Edwards syndrome (Trisomy 18)

Trisomy 18; severe congenital abnormalities and early mortality.

Patau syndrome (Trisomy 13)

Trisomy 13; midline defects, severe congenital anomalies, high mortality.

Turner syndrome

Monosomy X (45,X) in females; short stature, infertility; may be mosaic (45,X/46,XX) or have X structural abnormalities.

Klinefelter syndrome

Sex chromosome trisomy 47,XXY in males; small testes, gynecomastia, infertility.

Triple X syndrome

Sex chromosome trisomy 47,XXX in females; often asymptomatic.

XYY syndrome

Sex chromosome trisomy 47,XYY in males; tall stature and sometimes behavioral traits.

Trisomy 16

Autosomal trisomy typically not compatible with life; often aborts spontaneously.

Robertsonian translocation

Translocation between acrocentric chromosomes with fusion of long arms at the centromere; carriers may be normal but have recurrence risk for unbalanced offspring (e.g., t(14;21)).

Reciprocal translocation

Exchange of segments between non-homologous chromosomes; carriers usually healthy but offspring may be balanced or unbalanced.

Ring chromosome

Chromosome ends fuse to form a ring after terminal deletions; can be unstable and lead to variable phenotypes.

Inversion

A chromosome segment is inverted; can be paracentric (not including centromere) or pericentric (includes centromere). Can disrupt genes.

Paracentric inversion

Inversion that does not include the centromere.

Pericentric inversion

Inversion that includes the centromere.

Deletion

Loss of a chromosome segment; can be terminal (end) or interstitial (internal). If the centromere is lost, segregation is affected.

Terminal deletion

Deletion at the end of a chromosome.

Interstitial deletion

Deletion of a segment within the interior of a chromosome.

Duplication

Copying of a chromosome segment; can arise from unequal crossing over; often less deleterious than deletions.

Isochromosome

Chromosome with two identical arms due to misdivision at the centromere; typically results in distal loss of one arm.

Cri du Chat syndrome

Deletion of the distal short arm of chromosome 5 (5p-); cat-like cry and intellectual disability.

Williams syndrome

Microdeletion at 7q11.23 (including ELN and LIMK1); distinctive facial features and a sociable personality; cardiovascular issues.

Mosaicism

Presence of two or more cell lines with different karyotypes within one individual.

Hall criteria (Down syndrome)

Clinical criteria for Down syndrome; includes major signs (e.g., hypotonia, upslanting palpebral fissures, flat facial profile) and minor signs.

FISH (fluorescence in situ hybridization)

A molecular cytogenetic technique used to detect specific DNA sequences on chromosomes; helpful for identifying microdeletions or duplications.

CGH (comparative genomic hybridization)

A genome-wide technique to detect copy-number variations across the genome.

Recurrence risk (chromosomal rearrangements)

Probability that a chromosomal abnormality will recur in offspring due to parental rearrangements (e.g., translocations).