IllnessChromosomen-Aberration, postnatal

Cytogenetic diagnostics, the microscopic analysis of chromosomes, presents karyotypes. Karyotypes of chromosomally inconspicuous individuals comprise 46 chromosomes with 22 pairs of autosomes and 2 sex chromosomes, the gonosomes. Chromosomes are made up of DNA, carrying the genes in the genetic information (6 000 000 000 nucleotide pairs), of proteins and RNA. Chromosome analyses are used to examine the number and structure of the genetic carriers.

Chromosome representations are possible during the metaphase of the cell divisions, the chromosomes are condensed. Therefore, cells capable of division are examined, postnatal blood lymphocytes or amniotic, chorionic villus cells prenatally as well as fetal aborted tissue or in special cases fibroblasts from skin biopsies.

In order to display chromosomes, cells are cultivated, specially prepared and stained (GTG banding, etc.). At least 10 metaphases are evaluated under the light microscope, and karyograms (systematic arrangement of chromosomes) are made of at least 5 cells for structural assessment.

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Chromosomal defects are deviations from the normal number of chromosomes or their structure. All human chromosomes including the sex chromosomes (gonosomes) can be affected.Down syndrome (trisomy 21) is the most common autosomal aberration. Other autosomal trisomies are known as Edwards (trisomy 18) and Pätau syndrome (trisomy 13). Numerical aberrations of the gonosomes include Turner (45X) and Klinefelter syndrome (47XXY) as well as other abnormalities (47XXX, 47XYY etc.). Other autosomal trisomies are known as Edwards (trisomy 18) and Pätau syndrome (trisomy 13).Numerical aberrations of the gonosomes include Turner (45X) and Klinefelter syndrome (47XXY) and other abnormalities (47XXX, 47XYY etc.). Structural chromosome defects are caused by breaks and alterations in one or more chromosomes. Fragments are lost (deletion), inserted upside down (inversion) or doubled (duplication) or chromosomal pieces are exchanged (translocation). Only structural chromosomal changes that lead to DNA loss/gain are unbalanced. In case the regular arrangement of the genes is disturbed the activity might changed.

• Chromosomen-Störung, postnatal
• Chromosomen-Untersuchung
• Chromosomenaberration, postnatal
• Chromosomenstörung, postnatal
• Karyotype analysis
• Karyotyping, postnatal