1. Chromosomal Disorders

2. Chromosomal disorders
Having mild to severe (fatal) mental and/or physical deformities due to:
Adding or deleting part of a chromosome
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. Meiosis Starting cell Interphase Metaphase I Anaphase I Telophase I
Prophase I
Prophase II
Metaphase II
Anaphase II
Telophase II

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

6. Chromosomes condense and crossing-over
Prophase I
Chromosomes condense and crossing-over
occurs

7. The homologous pairs line up in the middle
Metaphase I
The homologous pairs line up in the middle

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

9. Telophase I
Cell has split in two

10. New spindle fibers begin to form
Prophase II
New spindle fibers begin to form

11. Chromosomes line up in the middle
Metaphase II
Chromosomes line up in the middle

12. Sister chromatids are pulled apart
Anaphase II
Sister chromatids are pulled apart

13. Each cell separates leaving 4 unidentical haploid cells
Telophase II
Each cell separates leaving 4 unidentical haploid cells

14. How do these disorders happen?
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

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

19. Turners Syndrome =
Missing X or Y chormosome

21. Klinefelters Syndrome =
having extra X chromosomes
XXY or XXXY