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  2. Genetics of Down syndrome - Wikipedia

    en.wikipedia.org/wiki/Genetics_of_Down_syndrome

    During meiosis, the chromosomal arrangement interferes with normal separation of chromosomes. Possible gametic arrangements are (see translocation karyotype figure): Offspring from one parent with a balanced translocation and the other parent who has normal chromosomes 1. translocated 14/21 and normal 14; 2. normal 14 and normal 21;

  3. Extrachromosomal DNA - Wikipedia

    en.wikipedia.org/wiki/Extrachromosomal_DNA

    Mitochondrial inheritance in humans: the mtDNA and its mutations are maternally transmitted. Inheritance of extrachromosomal DNA differs from the inheritance of nuclear DNA found in chromosomes. Unlike chromosomes, ecDNA does not contain centromeres and therefore exhibits a non-Mendelian inheritance pattern that gives rise to heterogeneous cell ...

  4. Down syndrome - Wikipedia

    en.wikipedia.org/wiki/Down_syndrome

    The extra chromosome content can arise through several different ways. The most common cause (about 92–95% of cases) is a complete extra copy of chromosome 21, resulting in trisomy 21. [92] [97] In 1–2.5% of cases, some of the cells in the body are normal and others have trisomy 21, known as mosaic Down syndrome.

  5. Polysomy - Wikipedia

    en.wikipedia.org/wiki/Polysomy

    Polysomy of chromosomes 1, 2, 4, 5, and 25 are also frequently involved in canine tumors. [16] Chromosome 1 may contain a gene responsible for tumor development and lead to changes in the karyotype, including fusion of the centromere, or centric fusions. [16] Aneuploidy due to nondisjunction is a common feature in tumor cells. [17]

  6. XXYY syndrome - Wikipedia

    en.wikipedia.org/wiki/XXYY_syndrome

    48,XXYY syndrome is a condition related to the X and Y chromosomes (the sex chromosomes). People normally have 46 chromosomes in each cell. Two of the 46 chromosomes, known as X and Y, are called sex chromosomes because they help determine whether a person will develop male or female sex characteristics. Females typically have two X chromosomes ...

  7. Human genetics - Wikipedia

    en.wikipedia.org/wiki/Human_genetics

    A karyotype is picture of all the chromosomes in the metaphase stage arranged according to length and centromere position. A karyotype can also be useful in clinical genetics, due to its ability to diagnose genetic disorders. On a normal karyotype, aneuploidy can be detected by clearly being able to observe any missing or extra chromosomes. [1]

  8. Chromosome abnormality - Wikipedia

    en.wikipedia.org/wiki/Chromosome_abnormality

    A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder is a missing, extra, or irregular portion of chromosomal DNA. [1] [2] These can occur in the form of numerical abnormalities, where there is an atypical number of chromosomes, or as structural abnormalities, where one or more ...

  9. International System for Human Cytogenomic Nomenclature

    en.wikipedia.org/wiki/International_System_for...

    [1] [2] Three chromosomal abnormalities with ISCN nomenclature, with increasing complexity: (A) A tumour karyotype in a male with loss of the Y chromosome, (B) Prader–Willi Syndrome i.e. deletion in the 15q11-q12 region and (C) an arbitrary karyotype that involves a variety of autosomal and allosomal abnormalities. [3]