1. Do Now 2.6 (HW check 8.14, 18) New Week (23)
Objectives:
Define karyotype, polyploidy, monosomy, trisomy, and nondisjunction
Analyze karyotypes to determine what, if any, chromosomal disorders an individual has.
Task:
1. List three processes other than mutation that produce genetic variation and diversity in sexually reproducing organisms.

2. Karyotype: Picture of chromosomes arranged by type

3. Polyploidy = more than 2n (i.e. 3n, 4n etc.)
In many organisms, (especially plants), polyploidy is common and normal. Every banana you eat is triploid, for example.
In humans and most animals, polyploidy is a dangerous condition associated with tumors and cancer.
The tetraploid mouse karyotype shown is from a tumor.

4. Monosomy and Trisomy
Monosomy refers to a missing chromosome from the typical diploid set
Trisomy refers to an extra chromosome

5. Nondisjunction: The cause of trisomy and monosomy
Nondisjunction: a mutation that occurs during meiosis I. Homologous chromosomes do not separate, which produces gametes with extra and missing chromosomes

6. Monosomy and Trisomy Disorders in Humans
Most instances of monosomy and trisomy produce an unviable zygote that spontaneously aborts (miscarries) very early in pregnancy.
With a few exceptions, the effects of nondisjunction mutations are very serious.

7. Sex Chromosome Nondisjunction is the Least Debilitating
47 XXX female: “super female.” Most individuals are unaware of the condition. They are at a high risk of producing offspring with sex chromosome trisomy however.
47 XYY males: “double Y males.” Many are unaware of the condition. Is associated with increased height, acne, and- perhaps- aggressive behavior
45 X females: “Turner Syndrome.” The only viable monosomy in humans
47 XXY: “Klienfelter Syndrome.” Male, with female secondary sex characteristics (breasts, less body hair, small testes, etc.)

8. Autosomal Trisomy Disorders
Trisomy 21: “Down Syndrome.” Significantly reduced IQ, characteristic features.
Trisomy 18: “Edwards Syndrome.” Severe disorder of heart and kidneys. If a fetus survives to birth, the median lifespan is 5-15 days
Trisomy 13: “Patau Syndrome.” Severe birth defects, including heart and kidney disorders, as well as malformations. 80% of infants do not survive beyond 1 year.

9. Recap
Karyotype: a picture of an organism’s chromosomes, arranged for analysis.
Polyploidy: a condition of three or more copies of each chromosome. Common in plants, associated with cancer in animals
Nondisjunction: the failure of a pair of homologous chromosomes to seperate during meiosis, producing gametes where n=22 or n=24
Monosomy – missing a chromosome (1 of a pair)
Trisomy – extra chromosome (3 of a pair)

10. Viable Nondisjunction Disorders
47 XXX female: “super female.”
47 XYY males: “double Y males.”
45 X females: “Turner Syndrome.”
47 XXY males: “Klienfelter Syndrome.”
Trisomy 21: “Down Syndrome.”
Trisomy 18: “Edwards Syndrome.”
Trisomy 13: “Patau Syndrome.”