1. How many chromosomes should a “normal” human have?
Are females XX or XY?
How do the words: DNA, gene and chromosomes relate?

2. 12.2: Chromosomal Disorders

3. Chromosomal disorders: Errors in the number or structure of a chromosome

4. Non-disjunction
Homologous chromosomes or sister chromatids fail to separate during meiosis.
Result: Gametes with abnormal # of chromosomes

5. Non-disjunction

6. Trisomy Having 3 of a particular chromosome.
Examples
Trisomy 21: Down syndrome
Trisomy 18: Edwards syndrome
- feet with rounded bottom
- crossed legs, clenched hands

7. Trisomies of Sex Chromosomes
XXX Female
XXY: Klinefelter Male
XYY: Male
Turner’s Syndrome
XO Female
45 Chromosomes

8. Chromosomal Duplications
Part of a chromosome is repeated.
Vary from fatal to developmental abnormalities.
Often leads to cancer in somatic cells

9. Chromosomal Deletions
Part of a chromosome is deleted.
Ex: Williams Syndrome
Partial deletion of chromosome 7

10. Chromosome Inversion
Fragment breaks and reverses on the same chromosome.
Not as lethal.

11. Chromosome Translocation
Fragment of one chromosome attaches to ANOTHER, DIFFERENT chromosome.
If there is an UNEQUAL swap of segments, results can serious.
List of Chromosome Disorders

12. Transposons Single genes that can move around.
“Jump” from one chromosome to another.
If they insert in the middle of an existing gene, that gene will be disrupted.