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Down Syndrome
Also known as Trisomy 21, causes developmental challenges.
Trisomy 21
Extra chromosome 21 leading to Down Syndrome.
Maternal Age Effect
Older mothers have higher risk for Trisomy 21.
Nondisjunction
Failure to separate chromosomes during meiosis.
Gamete Formation in Males
Begins at puberty, producing 1 billion sperm daily.
Sperm Production
Approximately 2.56 x 10^13 sperm in 70 years.
Genetic Combinations
Humans can produce 8,388,608 unique gametes.
Spindle Fibers
Formed during meiosis, critical for chromosome separation.
Meiosis Duration
Takes about three days in human males.
Prophase I Duration
Roughly 48 hours in male meiosis.
Anaphase I Timing
Spindle fibers about 48 minutes old in 48-year-old male.
Prophase II Duration
Approximately 90 minutes in male meiosis.
Anaphase II Timing
Spindle fibers about 90 minutes old in males.
Female Meiosis Complexity
Begins in utero, paused at Metaphase I until puberty.
Spindle Fiber Age in Females
In Anaphase I, spindle fibers are 1-2 days old.
Oogenesis
Egg formation, more complex than spermatogenesis.
Spermatogenesis
Sperm formation, continuous process in males.
Risk Factors for Nondisjunction
Older women and men equally likely to produce extra chromosome.
Nondisjunction Timing
Most likely during Anaphase I and II in egg formation.
Mitosis vs Meiosis
Mitosis does not form tetrads; meiosis does.
Crossing Over
Occurs during meiosis, increasing genetic variation.
Chromosome Count
Humans have 23 pairs of chromosomes.
Chromosome Abnormalities
Can lead to conditions like Down Syndrome.
Cell Cycle Regulation
Critical for normal cell division and cancer prevention.
