Sexual Reproduction and Meiosis

[Pages:71]Sexual Reproduction and Meiosis

Ultrasound: ? Chad Ehlers/Glow Images Copyright ? McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

Meiosis Overview

The form of cell division by which GAMETES, with HALF the number of CHROMOSOMES, are produced.

DIPLOID (2n) HAPLOID (n) Meiosis is SEXUAL reproduction. TWO divisions (MEIOSIS I and MEIOSIS

II).

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Meiosis Overview

Sex cells divide to produce GAMETES (sperm or egg).

Gametes have HALF the # of chromosomes.

Occurs only in GONADS (testes or ovaries).

Male: SPERMATOGENESIS -sperm

Female: OOGENESIS - egg or ova

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Diploid Cells Contain Two Homologous Sets of Chromosomes

Most cells in a sexually reproducing organism have two sets of chromosomes: one from the father and one from the mother.

Section 9.2

All karyotype photos: ? CNRI/Science Source

Figure 9.3

Diploid Cells Contain Two Homologous Sets of Chromosomes

Cells with two sets of chromosomes are called diploid cells. The image to the right shows all of the chromosomes from a diploid human cell.

Section 9.2

All karyotype photos: ? CNRI/Science Source

Figure 9.3

Diploid Cells Contain Two Homologous Sets of Chromosomes

The numbered chromosomes are called autosomes. These chromosomes are the same for both sexes.

Section 9.2

All karyotype photos: ? CNRI/Science Source

Figure 9.3

Diploid Cells Contain Two Homologous Sets of Chromosomes

The chromosomes denoted by a letter are the sex chromosomes. In humans, an individual with two X chromosomes is female, and an individual with one X and one Y chromosome is male.

Section 9.2

All karyotype photos: ? CNRI/Science Source

Figure 9.3

Diploid Cells Contain Two Homologous Sets of Chromosomes

Notice that each chromosome is paired with an equally-sized chromosome (except for when the X chromosome pairs with the smaller Y chromosome).

Section 9.2

All karyotype photos: ? CNRI/Science Source

Figure 9.3

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