Chapter 10: Meiosis and Sexual Reproduction

what is meiosis?

a special type of cell division used only for sexual reproduction that reduces the chromosome number by half, resulting in four genetically unique daughter cells.

when are chromosomes replicated?

before meiosis 1

what are the steps of meiosis 1?

prophase 1, metaphase 1, anaphase 1, telophase 1, and cytokinesis

what happens in prophase 1?

a spindle forms, the nuclear envelope fragments, the nucleolus disappears, each chromosome is duplicated and consists of two identical sister chromatids, homologous chromosomes pair up and physically align themselves side by side in a process called synapsis, crossing-over

what happens in metaphase 1

homologous pairs are arranged at the metaphase plate and bivalents align independently of one another

what happens in anaphase 1?

homologous chromosomes of each bivalent separate from one another and move towards opposite poles, sister chromatids do not separate

what happens in telophase 1?

daughter cells have one duplicated chromosome from each homologous pair

what happens in prophase 2?

chromosomes condense

what happens in metaphase 2?

chromosomes align at the metaphase late; they are no longer in pairs

what happens in anaphase 2?

sister chromatids separate and become daughter chromosomes that are not duplicated and move to opposite poles

what happens in telophase 2 and cytokinesis?

four haploid cells are produced, all genetically unique

what is crossing-over?

exchange of genetic material between non sister chromatids occur, resulting in genetic recombination

what is independent assortment?

random orientation and subsequent separation of maternal and paternal homologues during anaphase 1 leads to different combinations of chromosomes in the resulting of haploid cells.

what is the fundamental purpose of meiosis in sexually reproducing organisms?

produce haploid gametes that contain half the number of chromosomes as the parent cells. This reduction in chromosome number is essential for maintaining the correct diploid number in offspring and fertilization.

explain the concept of homologous chromosomes and their significance in meiosis.

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