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Chromosomal Disorders. Chromosomal disorders Having mild to severe (fatal) mental and/or physical deformities due to: 1.Adding or deleting part of a chromosome.

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Presentation on theme: "Chromosomal Disorders. Chromosomal disorders Having mild to severe (fatal) mental and/or physical deformities due to: 1.Adding or deleting part of a chromosome."— Presentation transcript:

1 Chromosomal Disorders

2 Chromosomal disorders Having mild to severe (fatal) mental and/or physical deformities due to: 1.Adding or deleting part of a chromosome 1.Having extra or missing chromosomes

3 How do these disorders happen? Mistakes before and during Parents never have the disorders! Can happen to anyone. Family history does not matter! Must follow: *Replication rules: Make an exact copy of the DNA with A-T and G-C *Law of segregation: homologous chromosomes must separate into different gametes *Crossing over- homologous chromosomes exchange pieces DNA meiosis!!!

4 Telophase II Anaphase II Metaphase II Prophase II Anaphase I Metaphase I Telophase I Starting cellInterphase Meiosis Prophase I

5 The cell grows bigger and a copy of each chromosome is made Interphase

6 Chromosomes condense and crossing-over occurs Prophase I

7 The homologous pairs line up in the middle Metaphase I

8 The homologous pairs are pulled away to opposite sides Anaphase I

9 Cell has split in two Telophase I

10 New spindle fibers begin to form Prophase II

11 Chromosomes line up in the middle Metaphase II

12 Sister chromatids are pulled apart Anaphase II

13 Each cell separates leaving 4 unidentical haploid cells Telophase II

14 How do these disorders happen? 1.Adding or deleting part of a chromosome Causes: Mistakes during DNA replication Or Mistakes during Crossing over

15 How do these disorders happen? 2. Having extra or missing chromosomes Causes: Nondisjunction: homologous chromosomes pairs or sister chromatids do not separate during meiosis. This leads to gametes (sperm or egg) that contain more or less than 23 chromosomes

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17 Common Chromosomal Disorders Down Syndrome = an extra 21 st chromosome

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19 Turners Syndrome = Missing X or Y chormosome

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21 Klinefelters Syndrome = having extra X chromosomes XXY or XXXY

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