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| The transmission of traits from one generation to the next is called inheritance, or heredity. |
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| Offspring differ somewhat in appearance from parents and siblings. |
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| The scientific study of heredity and hereditary variation. |
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| Parents endow their offspring with coded information in the form of hereditary units called genes. |
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| A single individual is the sole parent and passes copies of all its genes to its offspring. |
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| Results in greater variation than does asexual reproduction; two parents give rise to offspring that have unique combinations of genes inherited from the two parents. |
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| The generation-to-generation sequence of stages in the reproductive history of an organism, from conception to production of its own offspring. |
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| Homologous chromosomes (homologues) |
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Definition
| The chromosomes that make up a pair - that have the same length, centromere position, and staining pattern. The two chromosomes of each pair carry genes controlling the same inherited characters. |
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| Chromosomes besides the X and Y. |
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| Reproductive cells that have a single set of the 22 autosomes plus a single sex chromosome, either X or Y. |
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| A cell with a single chromosome set. |
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| The union of gametes when a haploid sperm cell from the father reaches and fuses with a haploid ovum of the mother. |
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| The resulting fertilized egg, from fertilization, that contains the two haploid sets of chromosomes bearing genes representing the maternal and paternal family lines. |
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| The zygote and all other cells having two sets of chromosomes. |
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| Alteration of generations |
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Definition
| Plants and some species of algae exhibit a third type of life cycle. It includes both diploid and haploid multicellular stages. |
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| The multicellular diploid stage of the alteration of generations. |
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Definition
| Meiosis in the sporophyte produces haploid cells called spores. |
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| A spore divides mitotically to generate a multicellular haploid stage called the gametophyte. |
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| During prophase I of meiosis, the duplicated chromosomes pair with their homologues, a process called synapsis. |
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| When the synaptonemal complex disappears in late prophase, the four closely associated chromatids of a homologous pair are visable in the light microscope as a tetrad. |
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Definition
| Also visable in the light microscope are X-shaped regions called chiasmata. |
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| The process called crossing over produces recombinant chromosomes, which combine genes inherited from our two parents. |
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