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CHAPTER 13 – MEIOSIS AND SEXUAL LIFE CYCLES VARIATIONS ON A THEME - The transmission of traits from one generation to the next is called inheritance, or heredity . - Along with inherited similarity, there is also variation . - Genetics is the scientific study of heredity and hereditary variation. 13.1 – OFFSPRING ACQUIRE GENES FROM PARENTS BY INHERITING CHROMOSOMES - Parents endow their offspring with coded information in the form of hereditary units called genes. - In animals and plants, reproductive cells called gametes are the vehicles that transmit genes from one generation to the next. - The DNA of a eukaryotic cell is packaged into chromosomes within the nucleus. - Humans have 46 chromosomes in their somatic cells —all cells of the body except the gametes and their precursors. - A gene’s specific location along the length of a chromosome is called the gene’s locus. - In asexual reproduction , a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes. - An individual that reproduces asexually gives rise to a clone , a group of genetically identical individuals. - In sexual reproduction , two parents give rise to offspring that have unique combinations of genes inherited from the two parents. - In contrast to a clone, offspring of sexual reproduction vary genetically from their siblings and both parents: They are variations on a common theme of family resemblance, not exact replicas. 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, from conception to production of its own offspring. - Karyotype – A display of the chromosome pairs of a cell arranged by size and shape. - Homologous chromosomes – A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother. Also called homologs, or a homologous pair.
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