BIOL 1000 Lecture Notes - Lecture 5: Chromosome Segregation, Allosome, Y Chromosome
Document Summary
Prokaryotic cell division and mitosis produce 2 daughter cells. Sexual reproduction produces unique offspring by union of male and female gametes (sperm and egg) Meiosis produces gametes with half the total chromosome number (46 -> 23). Mitosis, meiosis and fertilization are the stages of the animal life cycle. Animal follows mitosis, sperm/egg after meiosis and zygote after fertilization. Alleles are different versions of the same gene. Each gamete contains a different mix of alleles. Gene"s crossing over can happen anywhere along the chromosome length. It is more likely that it will happen the further apart, though. Human x chromosome is large (2350 genes) Human y chromosome is small, contains sry gene. Nondisjunction: failure of chromosome segregation at either meiosis i or meiosis ii. Euploid (normal # of chromosomes), aneuploids (extra/missing chromosomes) and. Polyploids (extra sets of all chromosomes (triploids, tetraploids etc. )) are results. Aneuploids usually prevent embryo development (down syndrome in humans is an exception)