1. GENETIC DISORDERS

2. Mutation –change in a gene resulting in change in genetic information
may be spontaneous or caused by a mutagen
Somatic mutations are usually not noticed
Gametic mutations are more severe
Not all mutations are bad!

3. SINGLE-GENE DEFECTS Congenital Defects: Inherited
Misplacement, insertion or deletion of one base pair
May result in incorrect amino acid
May result in shift of reading frame
Congenital Defects:
Visible at birth(club foot, spina bifida, congenital heart defects)
Caused by environmental factors (FAS, German measles)
Inherited
Sickle Cell Anemia, Cystic Fibrosis

4. INVERSIONS
Part of chromosome is flipped around 180° from its normal orientation.
Happens when chromosome breaks occur.
Broken piece may reattach, but not necessarily in the same orientation as before

5. TRANSLOCATIONS
Detachment of a segment of a chromosome, and reattachment to another non-homologous chromosome.
Some genes wind up on a completely different chromosome

6. ANOMALIES OF CHROMOSOME NUMBER
Polyploidy is common in plants
Gametes don’t reduce chromosome #
Result in cells with multiple copies of the genome

7. ANOMALIES OF CHROMOSOME NUMBER
Aneuploidy – more common in humans
Usually lethal before or shortly after birth
Monosomic and Trisomic

8. NONDISJUNCTION
Occurs when homologous chromosomes fail to separate after synapsis
Most nondisjunction events are lethal to the fetus

9. DOWNS SYNDROME Results from a third copy of chromosome 21
Called a trisomy
Individuals have 47 chromosomes in every body cell

10. SEX CHROMOSOME NONDISJUNCTION DISORDERS
TURNER SYNDROME
Occurs when nondisjunction causes a gamete to have a missing sex chromosome (X O)
Sterile females
1 in live births

11. SEX CHROMOSOME NONDISJUNCTION DISORDERS
KLINEFELTER’S SYNDROME
Genotype of XXY (extra sex chromosome)
Sterile males, breast development
1 in 800 live births

12. SEX CHROMOSOME NONDISJUNCTION DISORDERSXY
½ gamete lacking a sex chromosome
XO ¼
Turner’s syndrome
YO ¼
Will not survive
(LETHAL CONDITION)
½ gamete formed from nondisjunction
XXX ¼
“super female” usually normal
XXY ¼
Klinefelter’s syndrome X Y O XX XX