Post on 18-Jan-2018
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Mistakes in Meiosis
Non-Disjunction•a type of mistake in meiosis that happens to the CHROMOSOME
•It is the failure of homologous chromosomes to separate properly
2 things can happen
•a) Have extra chromosomes
•b) Missing chromosomes
Extra Chromosomes•EX: Down Syndrome•When chromosome # 21 does not fully separate, and there is an additional chromosome
•A person with down syndrome has 3 chromosomes instead of 2, which is called Trisomy 21
Extra Chromosome
•EX: Polyploidy•Polyploidy is when there is a total LACK of separation of homologous chromosomes
•The gamete (sperm/egg) inherits an entire EXTRA set of chromosomes
Polyploidy•Polyploidy is rare in animals, but if it occurs it will result in death of a zygote
•BUT, it is frequent in PLANTS•Plants that have polyploidy are larger, healthier, and are of greater commercial value
Polyploidy
Missing Chromosomes•If a chromosome is missing, the organism will most likely not survive
•It is referred to as “monosomy”
•EX: Turner syndrome
Turner Syndrome•Human females have only 1 single X chromosome instead of 2 X’s
How to detect Genetic Disorders•Cells are extracted from a
person•The Cells are stained to reveal a banding patterns
•Chromosomes are identified, and arranged in homologous pairs
•This chart is called a Karyotype, and is used to detect chromosomal abnormalities
•Chromosome PAIRS 1 -22 are called Autosomes
•Chromosome Pair 23 is called the sex chromosome
•XX is female•XY is Male •Sperm determines the sex of a baby (meaning it’s either X or Y), while the Egg is always X