In life, a lot of organisms pass on their genes to their offspring. Then that offspring passes their genes to their offspring, and it keeps going on and on. There are two forms of reproduction, sexual and asexual. Each form of reproduction has their own type of cell division consisting of either mitosis or meiosis. For asexual reproduction, cells undergo mitosis. For sexual reproduction, cells go through meiosis. In the process of meiosis, that is when a cell, specifically a diploid cell which contains two sets of chromosomes, one from the mother, one from the father, divides into two separate cells twice. Thus, resulting in a total of four haploid cells (gametes).
In meiosis, there are eight phases total, but are split into two sets of four. The first set is called Meiosis I and the second set is called Meiosis II. The main difference between Meiosis I and Meiosis II is that Meiosis I begins with 46 chromosomes and 92 chromatids. Meiosis II begins with 23 chromosomes, 46 chromatids, and finishes with both chromosomes and chromatids at 23. In lab, we learned about the four stages:
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There are some that are born a human genetic disorder. One of those disorders is called Trisomy 18, otherwise known as edward syndrome. In a lot of cases, Trisomy 18 is the result of having 3 copies of chromosome 18 in each cell. Normal healthy people without any genetic disorders only have 2 copies of chromosomes in each cell. Trisomy 18 is not a disorder that is inherited, it is random and occurs during the formation of egg and sperm in a cell division error called nondisjunction. Some major phenotypical characteristics of this disorder are small mouth, jaw and neck, and overlapping fingers when the hands are clenched. It is not common to see someone with Trisomy 18 because they all usually die before they reach their first year. If one was able to survive past age 1, then that individual would have severe intellectual