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ProfessorNondisjunction is a process during cell division where chromosomes fail to separate correctly. In Trisomy 21, an individual has three copies of chromosome 21 instead of the usual two, which is caused by nondisjunction during either meiosis I or meiosis II in the formation of gametes. When a gamete with an extra copy of chromosome 21 is fertilized, it results in an individual with Down syndrome.
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What is a common autosomal trisomy?
A common autosomal trisomy is trisomy 21, also known as Down syndrome. It occurs when a person has three copies of chromosome 21 instead of the usual two, resulting in characteristic physical features and developmental delays.
How many chromosomes will a zygote with trisomy have?
Meiotic nondisjunction. In meiosis I or II, chromosome pair 21 fail to separate correctly, leaving one gamete with an extra chromosome 21.
Is Down syndrome more severe in mitotic nondisjunction or meiotic nondisjunction?
Down syndrome is typically more severe in meiotic nondisjunction, as it is associated with an extra copy of chromosome 21 found in each cell of the affected individual. Mitotic nondisjunction can result in a mosaic pattern with some cells having the extra chromosome and others not.
What is a chromosomal disorder that could result from nondisjunction?
Disorders, such as Down's Syndrome, are caused by nondisjunction.
What are nondisjunction genes?
Nondisjunction is the failure of homologous chromosomes or chromatids to segregate during mitosis or meisos with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none. An example is Trisomy 21, which is also called Down's Syndrome. This person has 3 chromosome #21.Nondisjunction of genes occur during meiosis I when homologous chromosomes fail to separate or during meiosis II when there is unequal distribution of chromosomes. This leads to aneuploidy.
