Biology: Homologous Chromosomes

http://www.mindbites.com/lesson/1468-biology-homologous-chromosomes Professor Wolfe proposes two problems that have to be overcome during meiosis. One problem is that offspring have to have the same number of chromosomes as the parents, which means that the cells used in sexual reproduction need to have half the number of chromosomes as normal somatic cells. This means that meiotic division has to produce haploid cells. The second problem is the sorting of chromosomes. Each offspring will have to have not just the correct number of chromosomes, but also all the correct types of chromosomes. These two problems can be overcome by understanding that humans don't just have 46 chromosomes, but 23 pairs of chromosomes. A diploid cell is a cell with two copies of each chromosome. Sexual reproduction uses homologous chromosomes, which are chromosome pairs that have the same genetic composition but are derived from different parents. Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at http://www.thinkwell.com/student/product/biology. The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.