🧪 General Principles🟢 BasicChromosomal Disorders

Chromosomal Abnormalities in Disease

Changes in the number or structure of chromosomes that cause inherited syndromes and drive some cancers.

Key points

Chromosomal abnormalities are changes in the number or the structure of chromosomes, and they can disturb development or drive cancer.
Having an extra or a missing whole chromosome (aneuploidy) usually arises from faulty separation during cell division (non-disjunction).
Down syndrome is caused by an extra chromosome 21 (trisomy 21), Edwards syndrome by an extra 18, and Patau syndrome by an extra 13.
Sex-chromosome examples are Turner syndrome (a single X, written 45,X) and Klinefelter syndrome (an extra X, written 47,XXY).
Structural changes include deletions, duplications and translocations, in which a piece of one chromosome joins another.
Certain translocations drive cancer: the Philadelphia chromosome t(9;22), producing BCR-ABL1, in chronic myeloid leukaemia, and t(8;14), moving MYC beside the IGH gene, in Burkitt lymphoma.

Memory trick

Count and structure: trisomy 21 (Down), 18 (Edwards), 13 (Patau); 45,X (Turner), 47,XXY (Klinefelter); translocations drive CML (Philadelphia) and Burkitt.

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🧪 General Principles🟢 BasicChromosomal Disorders

Chromosomal Abnormalities in Disease

Changes in the number or structure of chromosomes that cause inherited syndromes and drive some cancers.

Key points

Chromosomal abnormalities are changes in the number or the structure of chromosomes, and they can disturb development or drive cancer.
Having an extra or a missing whole chromosome (aneuploidy) usually arises from faulty separation during cell division (non-disjunction).
Down syndrome is caused by an extra chromosome 21 (trisomy 21), Edwards syndrome by an extra 18, and Patau syndrome by an extra 13.
Sex-chromosome examples are Turner syndrome (a single X, written 45,X) and Klinefelter syndrome (an extra X, written 47,XXY).
Structural changes include deletions, duplications and translocations, in which a piece of one chromosome joins another.
Certain translocations drive cancer: the Philadelphia chromosome t(9;22), producing BCR-ABL1, in chronic myeloid leukaemia, and t(8;14), moving MYC beside the IGH gene, in Burkitt lymphoma.

Memory trick

Count and structure: trisomy 21 (Down), 18 (Edwards), 13 (Patau); 45,X (Turner), 47,XXY (Klinefelter); translocations drive CML (Philadelphia) and Burkitt.

All of Pathology More General Principles