Do Now 2.8Objectives:

1. Define karyotype, polyploidy, monosomy, trisomy, and nondisjunction

2. Analyze karyotypes to determine what, if any, chromosomal disorders an individual has.

Task:1. List three processes that produce variation and

diversity in sexually reproducing organisms.

Karyotypes: Chromosome Pictures

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.

Monosomy and Trisomy

• Monosomy refers to a missing chromosome from the typical diploid set

• Trisomy refers to an extra chromosome

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

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.

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.)

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.

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)

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.”