Spermatogenesis. I) Spermatocytogenesis: Spermatogonium Spermatid (2N, 4C) (1N, 1C) Genetic

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4 Spermatogenesis I) Spermatocytogenesis: Spermatogonium Spermatid (2N, 4C) (1N, 1C) Genetic II) Spermiogenesis: Spermatid Spermatozoan (1N, 1C) (1N, 1C) Metamorphic - loss of cytoplasm - addition of flagellum - addition of acrosome

5 SPERMATOGENESIS OÖGENESIS ANAPHASE I ANAPHASE II

6 SPERMATOGENESIS OÖGENESIS ANAPHASE I

7 ANAPHASE II

11 Fetus OOGENESIS (MAMMALIAN) 1. Oogonium (lx) (2n) undergoes cell growth and mitotic division to produce oogonia (nx) (2n). 2. Start of Meiosis I (Prophase I). Transformation of oogonium (1x) (2n) to 1º (primary) oocyte (1x) (2n) by passage through Prophase I up to zygotene/pachytene and cell growth. Birth 3. 1º oocyte (2n) arrested in Prophase I (zygotene/pachytene). 4. Growth of follicle, 1º oocyte (2n), and zona pellucida.

12 Puberty 5. Pre-ovulatory surge of luteinizing hormone (LH). 6. Resumption of Meiosis I. 7. 1º oocyte (lx) (2n) transformed to 2º oocyte (1x) (1n) and first polar body (1x) (1n) after completion of Meiosis I. 8. 2º oocyte arrested in Meiosis II (Metaphase II). Fertilization 9. Sperm (ln) penetration. 10. Meiosis II resumes. 11. Formation of zygote (2n). 12. Formation of second polar body (1n). 13. First polar body (1n) completes mitotic division to produce two more polar bodies (1n). 133

13 Fetus and after birth (before puberty) Oogonium 1 oocyte (Zygotene/Pachytene of Prophase I) 1 * LH surge - puberty Immature 2 oocyte (Prophase II) ovulation and 1 st polar body Movement of 2 oocyte to reproductive tract After puberty Mature 2 oocyte (Metaphase II) 2 * Fertilization (sperm penetration) Ootid (completion of Meiosis II; Metaphase II end of Telophase II) and 2 nd polar body Ootid Ovum differentiation

18 THEORIES OF SEX DETERMINATION 1. Sex is dependent upon genes on the chromosomes. 2. Sex is dependent upon the environment. 1) Examples of sex determination dependent upon genes on the chromosomes: A. Chromosomes Autosomes - all chromosomes other than sex chromosomes (same in diploid males and females). Sex chromosomes - Chromosomes particularly concerned with the determination of sex (X and Y and Z & W)

19 B. Normal chromosome compliment in some organisms. Organisms Sex chromosomes Autosomes Male Female Protenor X XX 6 pairs Humans XY XX 22 pairs Drosophila melanogaster XY XX 3 pairs Chickens XX XY 38 pairs Honey bee Male 16 Female 32 N 2N C. Sex chromosome types: Female Male XX and XO Male 1 less than female XX and XY Female has like sex chromosomes (homogametic) Male has unlike sex chromosomes (heterogametic) (i.e., mammals) XY and XX Male has like sex chromosomes (homogametic) (ZW) (ZZ) Female has unlike sex chromosomes (heterogametic) (i.e., chickens)

20 D. Some abnormalities: Drosophila Female Fertile Male Fertile Normal XX Yes XY Yes Abnormal XXY Yes X No Humans Female Fertile Male Fertile Normal XX Yes XY Yes Abnormal X No XXY No Turner's Klinefelter's Syndrome Syndrome 146

21 E. Method of sex determination: Protenor: 1X = male, 2X = female Humans: presence of Y = male (XY, XXY) absence of Y = female (X, XX, XXX ) Honey bee: male produced from an unfertilized egg (Parthenogenesis). Female produced from fertilized egg Chicken: male 2X, female XY Drosophila melanogaster a) Genetic balance theory: It is the ratio of the genes in the X chromosome(s) (which are female determining) to the genes in the autosomes (which are male determining) that determines sex in Drosophila melanogaster. b) The Y chromosome is necessary for fertility in Drosophila melanogater males.

22 Sex Determination Environmental: External Stimuli Ex. light, moisture, temperature, chemical. Internal Stimuli Ex. hormonal Genetic: Autosomes Gonosomes (sex chromosomes)

23 Terms: i) Homogametic sex: produces one kind of gamete in reference to the sex chromosomes. ii) Heterogametic sex: produces two kinds of gametes in reference to the sex chromosomes. 147

24 Bonellia viridis Green Spoon Worm Dinophilus taeniatus No Common Name Equisetum sp. Horsetail Plant Cucumis sativus Cucumber Cucumis melo Muskmelon Alligator mississippiensis

Gametogenesis. To complete this worksheet, select: Module: Continuity Activity: Animations Title: Gametogenesis. Introduction

Gametogenesis. To complete this worksheet, select: Module: Continuity Activity: Animations Title: Gametogenesis. Introduction Gametogenesis To complete this worksheet, select: Module: Continuity Activity: Animations Title: Gametogenesis Introduction 1. a. Define gametogenesis. b. What cells are gametes? c. What are the two cell