Introduction to Chromosome Disorders

Introduction to Chromosome Disorders

• Chromosome disorders are genetic conditions arising from abnormalities in chromosome structure or number.
• These abnormalities can occur during the formation of reproductive cells (meiosis) or early stages of embryonic development.
• They can result in a wide range of physical, mental, and developmental issues.
• Some disorders are evident at birth, while others may not manifest until later in life.
• The severity of symptoms varies greatly between individuals with the same disorder.

Types of Chromosome Disorders

• Numerical abnormalities: Involve extra or missing chromosomes.
  • Trisomy: Presence of an extra chromosome (e.g., Down syndrome - Trisomy 21).
  • Monosomy: Absence of a chromosome (e.g., Turner syndrome - Monosomy X).
• Structural abnormalities: Affect the structure of a chromosome.
  • Deletions: Loss of a segment of a chromosome.
  • Duplications: Presence of an extra copy of a segment.
  • Inversions: Rearrangement of a segment within a chromosome.
  • Translocations: Exchange of segments between different chromosomes.
• Mosaicism: A combination of cells with normal and abnormal chromosomes.

Causes of Chromosome Disorders

• Errors during meiosis: The process of cell division that produces egg and sperm cells is susceptible to errors like non-disjunction, where chromosomes fail to separate properly.
• Environmental factors: Certain exposures (e.g., radiation) may increase the chance of chromosome damage but are not the primary cause.
• Parental age: The risk of chromosome abnormalities increases with maternal age.
• Unknown factors: Some cases appear to arise from unknown causes.

Down Syndrome (Trisomy 21)

• Characteristics: Intellectual disability, characteristic facial features, heart defects, and other health issues, are common.

Turner Syndrome (Monosomy X)

• Characteristics: Affecting females, short stature, ovarian failure, and often other physical features.

Cri-du-chat Syndrome

• Characteristics: A deletion on chromosome 5, high-pitched cry, and intellectual disability are key features.

Klinefelter Syndrome

• Characteristics: Affecting males, presence of an extra X chromosome, reduced fertility, and some physical characteristics.

Genetic Testing for Chromosome Disorders

• Karyotyping: Examination of chromosomes under a microscope to identify structural or numerical abnormalities.
• FISH (Fluorescent in situ hybridization): Uses probes to detect specific genetic material on chromosomes.
• Array Comparative Genomic Hybridization (aCGH): A powerful technique that looks for tiny changes in chromosomes.

Management and Support for Chromosome Disorders

• Therapies can address specific problems.
• Support groups provide emotional and practical assistance for families.
• Early intervention programs help maximize development for some individuals.