Chromosomal Abnormalities and Genetic Disorders

Chromosomal Disorders

Changes in chromosome number or structure.

Aneuploidy

Abnormal number of chromosomes in a cell.

Monosomy

One less copy of a chromosome pair.

Trisomy

An extra copy of a chromosome.

Meiosis Failure

Issues in meiotic chromosome separation.

Karyotype

Complete set of chromosomes in cells.

Metacentric Chromosomes

Centromere near the center of the chromosome.

Submetacentric Chromosomes

Centromere off-center, one arm longer.

Acrocentric Chromosomes

Centromere near one end of the chromosome.

Gene Address

Combination of numbers and letters indicating gene location.

Polyploidy

Presence of more than one pair of chromosomes.

Translocations

Unusual rearrangement of chromosome segments.

Deletions

Missing parts of chromosomes.

Duplications

Extra copies of chromosome segments.

Inversions

Chromosome segment inverted within its original position.

Diploid

Two complete sets of chromosomes.

Triploidy

Complete extra set of chromosomes (69 total).

Down Syndrome

Trisomy 21: 47,XX,+21.

Edwards Syndrome

Trisomy 18: 47,XX,+18.

Patau Syndrome

Trisomy 13: 47,XX,+13.

Turner Syndrome

45,X: single X chromosome.

Klinefelter Syndrome

47,XXY: extra X chromosome.

Cytogenetics

Study of chromosomes and their abnormalities.

Facial Characteristics of Down Syndrome

Upslanting eyelids, protruding tongue, low nasal bridge.

Causes of Chromosomal Disorders

Ionizing radiation, viral infections, chemical toxins.

Giemsa Bands

Banding pattern used to identify chromosomes.

Chromosome Classification

Based on centromere position and structure.

Triploid Fetuses

Typically die shortly after birth.

Dispermy

Fertilization of an egg by two sperm.

Trisomy 21

Presence of an extra chromosome 21 in cells.

Facial Characteristics

Upslanting eyelids, protruding tongue, low nasal bridge.

Intellectual Disability

Mild to moderate; IQ ranges from 40 to 60.

Incidence of Down Syndrome

Occurs in 1 in 700 live births.

Respiratory Disease

Second leading cause of death in Down Syndrome.

Meiotic Nondisjunction

Failure of chromosomes to separate during meiosis.

Cleft Lip and Palate

Common defect in Patau Syndrome patients.

Life Expectancy in Patau Syndrome

Average lifespan of survivors is about 10 years.

Symptoms of Klinefelter Syndrome

Includes low testosterone, gynecomastia, and sterility.

Incidence of Turner Syndrome

Occurs in 1 in 5,000 births.

Jacob's Syndrome

Trisomy XYY; typically normal physical and mental health.

Triple X Syndrome

Females with an extra X chromosome; often taller.

Dosage Compensation

Equal gene expression from X chromosomes in females.

X-Inactivation

Process where one X chromosome is silenced.

Barr Body

Inactivated X chromosome, dense and transcriptionally inactive.

Mary Lyon

Proposed the Lyon hypothesis on X-inactivation.

Mosaicism in Females

Females express genes from both X chromosomes.

Calico Cats

Females with orange and black patches due to X-inactivation.

X Chromosome and Coat Color

Gene for color located on the X chromosome.

Heterozygous Females

Carry two different alleles for coat color.

Chromosomal Abnormalities

Includes numerical disorders and structural rearrangements.

Sex Chromosome Variation

Includes Klinefelter, Turner, Jacob's, and Triple X syndromes.

Nondisjunction

Chromosomal error leading to an abnormal number.

Clinical Characteristics

Observable traits associated with chromosomal disorders.