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Chapter 13 - Meiosis and Sexual Life Cycles


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the transmission of traits from one generation to the next
the scientific study of heredity and hereditary variation
hereditary units that hold genetic information; passed on from parent to offspring; segments of DNA
a gene’s specific location along the length of a chromosome
Asexual reproduction
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
a group of genetically identical individuals
Sexual reproduction
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
Life cycle
the generation-to-generation sequence of stages in the reproductive history of an organism, from conception to production of its own offspring
a method of organizing the chromosomes of a cell in relation to number, size, and type; usually prepared using lymphocytes
Homologous chromosomes
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
Sex chromosomes
chromosomes X and Y (nonhomologous chromosomes)
all chromosomes except sex chromosomes
sex cells that contain a single set of chromosomes and is called haploid
another term for fertilization; union of gametes to form a zygote
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
a process during prophase I in which the duplicated chromosomes pair with their homologues
the grouping of the four closely associated chromatids of a homologous pair that are visible through a light microscope
X-shaped regions visible through the light microscope that represent a crossing of nonsister chromatids; physical manifestations of crossing over
Interphase I
stage during which chromosomes replicate, resulting in two genetically identical sister chromatids that remain attached
Prophase I
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
Metaphase I
stage of meiosis in which chromosomes are arranged on the metaphase plate in homologous pairs
Anaphase I
stage of meiosis in which the spindle apparatus moves the chromosomes toward the poles of the cell
Telophase I and cytokinesis
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
Prophase II
stage of meiosis in which the spindle apparatus forms and chromosomes progress toward the metaphase II plate
Metaphse II
stage of meiosis that resembles mitotic metaphase; chromosomes line up at the metaphase II plate
Anaphase II
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
Telophase II and cytokinesis
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
Crossing over
a process the produces individual chromosomes that combine genes inherited from our two parents; occurs during prophase of meiosis I

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