Topic 4.2 - Boles
3
Karyotyping In karyotyping, chromosomes are arranged in pairs according to their size and structure. Karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome abnormalities. Non-disjunction can lead to changes in chromosome number. An example of this is Down syndrome (trisomy 21). A trisomy occurs when there are three copies of a chromosome in a cell. This is a result of non- disjunction during meiosis, followed by fertilization with another gamete. Meiosis is a reduction division of a diploid nucleus to form haploid nuclei. NON- DISJUNCTION IB BIOLOGY HL T O P I C 4 . 2 M EIOSIS HOMOLOGOUS CHROMOSOMES Homologous chromosomes are two identical sets of chromosomes that come from the mother and the father. They are the same size and structure, and they contain the same genes in the same locations.
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Transcript of Topic 4.2 - Boles
Karyotyping
In karyotyping, chromosomes are arranged in pairs according to their size and structure. Karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome abnormalities.
Non-disjunction can lead to changes in chromosome number. An example of this is Down syndrome (trisomy 21). A trisomy occurs when there are three copies of a chromosome in a cell. This is a result of non-disjunction during meiosis, followed by fertilization with another gamete.
Meiosis is a reduction division of a diploid nucleus to form haploid nuclei.
NON-DISJUNCTION
I B B I O L O G Y H L
T O P I C 4 . 2
MEIOSIS
HOMOLOGOUS CHROMOSOMES
Homologous chromosomes are two
identical sets of chromosomes that come from the mother and the
father. They are the same size and structure, and they contain the same
genes in the same locations.
Process of Meiosis
Karyotype AnalysisSince there are two X chromosomes and no Y, the person with whom the karyotype corresponds is female. Because there are two of each chromosome and no extras, non-disjunction has not occurred.
