Do Now 2.8. 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 that produce variation and diversity in sexually reproducing organisms.
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Do Now 2.8 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 that produce variation and diversity in sexually reproducing organisms.
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.)
AutosomalTrisomy 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.”