BIO152H5 Lecture Notes - Lecture 5: Homologous Chromosome, Sister Chromatids, Nuclear Membrane
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There are 23 types of chromosomes and 2 chromosomes of each type (homologous chromosomes, one from each parent). X and y are sex chromosomes: xx" represent female, xy" represent male. Sexual reproduction involves the alternation of meiosis and fertilization. Meiosis is a mechanism for diversity: the parent nucleus produces four haploid daughter nuclei, each different from the parent and from its sister. A) each chromosome replicates prior to undergoing meiosis, similar as mitosis, where chromosomes replicate before undergoing cell division. B) during meiosis, chromosomes number in each cell is reduced. Will have 4 daughter cells as a result. C) a full complement of chromosomes in restored during fertilization. Via meiosis, you produce gametes, which will produce diploid gametes. Meiosis 1 is the first division of meiosis. Meiosis 1 begins with a diploid parent cell and produces two daughter cells that will then progress through meiosis 2.
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Which statements pertaining to genetic variability are correct? Check all that apply (note that wrong answers will be deducted from right answers)!
Crossing over is defined by the exchange of chromosome pieces during metaphase one of meiosis. |
If a germ cell (i.e. parent cell before meiosis) had only two pairs of homologous chromosomes (i.e. 4 chromosomes total) there are 2 possible combinations of maternal and paternal chromosomes in gametes. |
Siblings produced by sexual reproduction are different because sperms are different from one another and eggs are different from one another, and the combination of an egg and sperm is basically unique. |
Random fertilization means that all possible combinations of eggs and sperm are equally likely, i.e. it is pure chance which sperm fuses with which egg. |
Individual chromosomes contain thousands of genes. This means that during each crossing over event, more than one gene is exchanged between paternal and maternal chromosomes. |