1. MISTAKES IN MEIOSIS

2. MISTAKES IN SEPARATION
Aneuploidy:
Error during meiosis
Separation of chromosomes doesn't take place properly resulting in cells have too many or too few chromosomes
Caused by: NONDISJUNCTION
-Failure of homologous chromosomes to separate in meiosis I
-Failure of sister chromatids to separate in meiosis II

3. EXAMPLES
MONOSOMY:
Sex cell missing one chromosome (in place of a homologous pair)
POLYSOMY:
Condition where there are more chromosomes than required (in place of a homologous pair)
POLYPLOIDY:
Non-disjunction of all of the chromosomes in a gamete that unites with a haploid gamete to produce 3 sets of chromosomes (3n)

5. MISTAKES IN CROSSING OVER
Pieces of genetic information are exchanged but do not re-attach properly
Deletion: When exchanged information does not reattach to the chromosome
Inversion: Segment of DNA reattaches to chromosome but in the reverse order
Duplication: The exchanged information is repeated on the chromosome
Translocation: Movement of information from one chromosome to a non-homologous chromosome

7. KARYOTYPES:
A karyotype is an organized picture of a person’s chromosomes
Test to examine chromosomes
Can help identify genetic problems by:
Counting the number of chromosomes (too many or too few)
Looking for structural changes in chromosomes
The test can be performed on almost any tissue:
Amniotic fluid
Blood
Bone marrow
Tissue from the placenta

8. KLINEFELTER SYNDROME Not inherited Genetic Changes:
Male with extra copy of X chromosome (XXY)
Problem:
Nondisjunction causes polysomy
Symptoms:
-Low levels of testosterone
-Breast development
-Decreased body and facial hair
-Abnormal sexual development
-Learning disabilities

9. TURNER SYNDROME Not inherited Genetic Changes:
Note - cannot have Y0, fetus will not survive
TURNER SYNDROME
Not inherited
Genetic Changes:
Missing/damaged X chromosome (X0)
Problem:
-Monosomy caused by nondisjunction
-Deletion or inversion
Symptoms:
-Shorter
-Webbed neck
-Skeletal abnormalities
-Heart defect
-Kidney problems

10. TRIPLE X: Not inherited Genetic Changes:
Female with 3 X chromosomes (XXX)
Problem:
Nondisjunction causes polysomy
Symptoms:
Taller
Increased incidence of learning disabilities
Normal otherwise

11. 47 XYY Not inherited Genetic Changes:
Extra Y chromosome in males (XYY)
Problem:
Nondisjunction causes polysomy
Symptoms:
Taller
No physical problems
Some risk of learning disabilities