LSCI 204 Lecture Notes - Lecture 5: Dystrophin, Barr Body, Xxxo
8 Feb 2018
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Chapter 4: extensions and modifications of basic principles. Sex is determined by a number of different mechanisms. There are several different mechanisms of sex determination. The x and y chromosomes pair during meiosis, even though they are not homologous (the genes located on each are different) Sexual reproduction: alternates between haploid and diploid states. Most organisms have two sexual phenotypes, male and female. Sexual reproduction consists of an alternation of haploid and diploid cells. Fertilization (fusion of gametes) produces a diploid zygote. Male and female gametes differ in size. Every species has a different number of chromosomes. Composed of chromatin a complex of dna and proteins. The x and y chromosomes are homologous only at the pseudoautosomal region (the extremes of the chromosomes), which are essential for x y chromosome pairing in meiosis in the male. Equal number of male and female offspring. No sex chromosomes, only the sex-determining genes. Found in some plants, fungi, protozoans, and fish.
