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Chromosomal Abnormalities Changes in chromosome structure or number.

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Presentation on theme: "Chromosomal Abnormalities Changes in chromosome structure or number."— Presentation transcript:

1 Chromosomal Abnormalities Changes in chromosome structure or number

2 Alteration of chromosome number ▫Nondisjunction- homologous chromosomes don’t separate during meiosis I or sister chromatids don’t separate during Meiosis II ▫trisomy  cells have 3 copies of a chromosome ▫monosomy  cells have only 1 copy of a chromosome

3 Alteration of chromosome number all with incorrect number1/2 with incorrect number error in Meiosis 1 error in Meiosis 2

4 Karyotyping Somatic cells are isolated Treat with a chemical to stimulate mitosis Photograph taken of metaphase chromosomes Arrange chromosomes according to: ▫ Size ▫Banding pattern ▫Centromere position Observe the patterns karyotype/http://learn.genetics.utah.edu/content/begin/traits/ karyotype/

5 What observations can you make? Normal Human MaleNormal Human Female

6

7 Down syndrome Trisomy 21 ▫3 copies of chromosome 21 ▫1 in 700 children born in U.S. Chromosome 21 is the smallest human chromosome ▫but still severe effects Frequency of Down syndrome correlates with the age of the mother

8 Down syndrome & age of mother Mother’s age Incidence of Down Syndrome Under 30<1 in in in in in in in in in in in in in 12

9 Human chromosome disorders High frequency in humans ▫most embryos are spontaneously aborted ▫alterations are too disastrous Certain conditions are tolerated ▫upset the balance less = survivable ▫but characteristic set of symptoms = syndrome

10 Alterations of chromosome structure deletion ▫loss of a chromosomal segment duplication ▫repeat a segment inversion ▫reverses a segment translocation ▫move segment from one chromosome to another

11 Alterations of Chromosome Structure


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