Chromosomal anomalies or abnormalities changes in number or structure of chromosomes

Chromosomal anomalies—also known as chromosomal abnormalities or disorders—are changes in the number or structure of chromosomes that can lead to developmental issues, birth defects, or genetic diseases.

🧬 Types of Chromosomal Anomalies
1. Numerical Abnormalities
These involve a change in the number of chromosomes:

Trisomy: An extra chromosome (e.g., Trisomy 21 = Down syndrome)

Monosomy: Missing a chromosome (e.g., Turner syndrome = single X chromosome)

Polyploidy: More than two complete sets of chromosomes (e.g., triploidy, tetraploidy)

2. Structural Abnormalities
These involve changes in the chromosome’s shape or content:

Deletions: Loss of a chromosome segment

Duplications: Extra copies of a chromosome segment

Translocations: Segment moves to a different chromosome

Inversions: Segment flips within the same chromosome

Ring chromosomes: Ends of a chromosome join to form a ring

⚠️ Causes
Errors during meiosis or mitosis

Environmental factors (e.g., radiation, toxins)

Inherited mutations

Spontaneous genetic changes during early development

🧪 Diagnosis
Karyotyping: Visual analysis of chromosomes

FISH (Fluorescence In Situ Hybridization): Detects specific DNA sequences

Noninvasive prenatal testing (NIPT): Screens fetal DNA in maternal blood

Chromosomal microarray: Detects small deletions/duplications

👶 Common Examples
Syndrome Chromosomal Change Key Features
Down syndrome Trisomy 21 Intellectual disability, facial features
Turner syndrome Monosomy X (45,X) Short stature, infertility
Klinefelter syndrome XXY (47 chromosomes) Male infertility, learning difficulties
Patau syndrome Trisomy 13 Severe intellectual and physical issues
Edwards syndrome Trisomy 18 Growth restriction, organ defects
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