Chapter 13 - Meiosis And Sexual Life Cycles

Front 1

Heredity

Back 1

the transmission of traits from one generation to the next

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Genetics

Back 2

the scientific study of heredity and hereditary variation

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Gene

Back 3

hereditary units that hold genetic information; passed on from parent to offspring; segments of DNA

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Locus

Back 4

a gene’s specific location along the length of a chromosome

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Asexual reproduction

Back 5

a process in which a single individual is the sole parent and passes copies of all its genes on to its offspring; offspring is usually genetically identical to parent

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Clone

Back 6

a group of genetically identical individuals

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Sexual reproduction

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a reproductive process that results in greater variation than asexual reproduction; two parents give rise to offspring that have unique combinations of genes inherited from the two parents; offspring differ from both parents and siblings genetically

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Life cycle

Back 8

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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Karyotype

Back 9

a method of organizing the chromosomes of a cell in relation to number, size, and type; usually prepared using lymphocytes

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Homologous chromosomes

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the chromosomes that make up a pair – that have the same length, centromere position, and staining pattern; also called homologues; chromosomes of each pair carry genes controlling the same inherited characteristics

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Sex chromosomes

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chromosomes X and Y (nonhomologous chromosomes)

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Autosomes

Back 12

all chromosomes except sex chromosomes

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Gametes

Back 13

sex cells that contain a single set of chromosomes and is called haploid

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Syngamy

Back 14

another term for fertilization; union of gametes to form a zygote

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Meiosis

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a form of cell division in which the number of a haploid number of chromosomes is passed on from cell to cell; occurs only in the ovaries and testes

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Synapsis

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a process during prophase I in which the duplicated chromosomes pair with their homologues

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Tetrad

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the grouping of the four closely associated chromatids of a homologous pair that are visible through a light microscope

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Chiasmata

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X-shaped regions visible through the light microscope that represent a crossing of nonsister chromatids; physical manifestations of crossing over

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Interphase I

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stage during which chromosomes replicate, resulting in two genetically identical sister chromatids that remain attached

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Prophase I

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stage of meiosis that involves the disintegration of the nuclear envelope, condensation of the chromosomes and synapsis; centrosomes also move apart and begin to form spindle fibers; composes roughly 90% of the time required for meiosis

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Metaphase I

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stage of meiosis in which chromosomes are arranged on the metaphase plate in homologous pairs

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Anaphase I

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stage of meiosis in which the spindle apparatus moves the chromosomes toward the poles of the cell

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Telophase I and cytokinesis

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stages of meiosis that generally occur concurrently; each pole has a haploid chromosome set, but each chromosome still has two sister chromatids; cleavage furrows form in animal cells and cell plates form in plant cells

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Prophase II

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stage of meiosis in which the spindle apparatus forms and chromosomes progress toward the metaphase II plate

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Metaphse II

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stage of meiosis that resembles mitotic metaphase; chromosomes line up at the metaphase II plate

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Anaphase II

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stage of meiosis in which the centromeres of sister chromatids separate and the sister chromatids of each pair move toward opposite poles of the cell

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Telophase II and cytokinesis

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stage of meiosis in which nuclei form at opposite poles of the cell and cytokinesis occurs; results in four daughter cells which each possess a haploid number of unreplicated chromosomes

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Crossing over

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a process the produces individual chromosomes that combine genes inherited from our two parents; occurs during prophase of meiosis I