Concept 13.2 Fertilization and meiosis alternate in sexual life cycles. A life cycle is the generation-to-generation sequence of stages in the reproductive history of an organism. ○ A life cycle starts at the conception of an organism and continues until the organism produces its own offspring. Human cells contain sets of chromosomes. In humans, each somatic cell (all cells other than the sperm or ovum) has 46 chromosomes. Each chromosome can be distinguished by its size, position of the centromere, and pattern of staining with certain dyes. Images of the 46 human chromosomes can be arranged in pairs in order of size to produce a karyotype display. ○ The two chromosomes in a pair have the same length, centromere position, and staining pattern. ○ These homologous chromosome pairs carry genes that control the same inherited characters. Two distinct sex chromosomes, the X and the Y, are an exception to the general pattern of homologous chromosomes in human somatic cells. ○ The pattern of inheritance of the sex chromosomes determines an individual’s sex.
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This note was uploaded on 01/04/2012 for the course BSC BSC1005 taught by Professor Orlando,rebecca during the Fall '10 term at Broward College.