Introduction to Chromosome Disorders

Study Notes

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.

Description

This quiz covers the basics of chromosome disorders, including their causes and types. It explores numerical and structural abnormalities that can lead to various genetic conditions, both at birth and later in life. Understand how these disorders impact individuals differently.