Problems Homologous chromosome

1. meiosis 2. meiosis ii 3. fertilization 4. zygote nondisjunction when chromosomes fail separate resulting in gain or loss of chromosomes. in left image blue arrow indicates nondisjunction taking place during meiosis ii. in right image green arrow indicating nondisjunction taking place during meiosis i.

there severe repercussions when chromosomes not segregate properly. faulty segregation can lead fertility problems, embryo death, birth defects, , cancer. though mechanisms pairing , adhering homologous chromosomes vary among organisms, proper functioning of mechanisms imperative in order final genetic material sorted correctly.

nondisjunction

proper homologous chromosome separation in meiosis crucial sister chromatid separation in meiosis ii. failure separate known nondisjunction. there 2 main types of nondisjunction occur: trisomy , monosomy. trisomy caused presence of 1 additional chromosomes in zygote compared normal number, , monosomy characterized presence of 1 fewer chromosome in zygote compared normal number. if uneven division occurs in meiosis i, none of daughter cells have proper chromosomal distribution , severe effects can ensue, including down’s syndrome. unequal division can occur during second meiotic division. nondisjunction occurs @ stage can result in normal daughter cells , deformed cells.