Reproduction and Gametogenesis

Vocabulary flashcards covering topics on reproduction, gametogenesis, embryonic sex determination, meiosis, and reproductive hormonal control based on the lecture notes.

Asexual Reproduction

A biological process in which unicellular organisms reproduce by mitotic divisions, producing offspring that are genetically identical to the single parent.

Sexual Reproduction

A biological process typically requiring the involvement of two individuals or gametes (egg and sperm), one from each opposite sex, to produce genetically unique offspring.

Egg Cell

A large, non-motile haploid gamete containing a protective outer coat, inner energy-supplying yolk, and abundant stored proteins, RNAs, ribosomes, and mitochondria.

Zona Pellucida

The protective outer coat surrounding an egg cell.

Sperm Cell

A small, motile haploid gamete equipped with a flagellum, abundant mitochondria, centrioles, and an acrosomal vesicle designed to deliver paternal DNA.

Acrosomal Vesicle

A specialized Golgi-derived structure in the head of a sperm cell that allows it to bind to and penetrate the egg coat.

Primordial Germ Cells

Early embryonic cells (gonocytes) originating from the epiblast of the yolk sac that migrate to the bipotent gonads and possess the developmental potential to become gametes.

Genomic Event

A mechanism or process occurring early in development that leads to cell fate specification or differentiation.

P-granules

Complexes of RNA and proteins in C. elegans cytoplasm that localize to the posterior region of the zygote before the first cleavage to specify germ cell fate.

BMP 4

Bone morphogenetic protein 4; a signaling molecule activated downstream of Wnt in mouse embryos that restricts primordial germ cells to a germ-line fate.

SRY Gene

A gene located on the short arm of the Y chromosome that initiates male gonadal development by activating SOX9 transcription and blocking Wnt and Rspo1.

SOX9

A transcription factor upregulated by SRY and FGF9 during male gonadal development that promotes testis differentiation and activates Anti-Müllerian Factor.

FGF9

A signaling factor in male sex determination that promotes the upregulated expression of SOX9.

$\beta$\text{-Catenin}

A protein increased by WNT4 and Rspo1 that interacts with transcription factors to promote ovarian development and inhibit testicular development.

Müllerian Ducts

Embryonic ducts present in undifferentiated gonads that develop into female internal genitalia (uterus, oviducts, cervix) in the absence of AMF and testosterone.

Wolffian Ducts

Embryonic ducts maintained by testosterone that develop into male internal genitalia (epididymis, vas deferens, seminal vesicles).

Anti-Müllerian Factor

A hormone produced by Sertoli cells in fetal testes (activated by SOX9) that causes the regression of Müllerian ducts and prevents female internal genitalia development.

Androgen Insensitivity Syndrome

A condition in karyotypical $XY$ individuals caused by an inability to respond to androgen hormones, leading to impaired male genital development or a full female presenting habitus.

Mitosis

A process of cell division in somatic cells and precursor germ cells where chromosomal number is maintained, producing two identical daughter cells.

Meiosis

A one-way cell division process in germ cells that halves the chromosomal number to produce haploid gametes with varied genotypes.

Meiosis I

The first division round of meiosis in which homologous chromosome pairs separate into two haploid intermediate cells.

Meiosis II

The second division round of meiosis in which sister chromatids separate, resulting in four haploid daughter cells.

Segregation

The random alignment and separation of maternal and paternal homologous chromosome pairs during metaphase I and anaphase I.

Crossing Over

The exchange of DNA between paired homologous chromosomes that occurs during prophase I of meiosis I.

Gametogenesis

The process by which precursor diploid or haploid germ cells undergo division and differentiation to form mature haploid gametes.

Nondisjunction

The failure of homologous chromosomes to separate in meiosis I, or sister chromatids in meiosis II, resulting in cells with abnormal chromosome numbers (aneuploidy).

Klinefelter Syndrome

A genetic condition caused by nondisjunction where an individual inherits an extra X chromosome ($XXY$), leading to symptoms like infertility, reduced testes, and gynecomastia.

Turner Syndrome

A genetic condition where an individual has an $XX$ karyotype with one missing or partial X chromosome, leading to delayed growth, non-developing ovaries, webbed neck, and infertility.

Oogonia

Immature, mitotically active female germ cells in the embryonic ovary that divide to produce primary oocytes.

Primary Oocytes

Female germ cells that begin meiosis during fetal development and remain arrested in prophase I until puberty.

Secondary Oocyte

The large haploid cell resulting from uneven cytokinesis during meiosis I of a primary oocyte, which arrests in metaphase II until fertilization.

Polar Body

A small haploid cell with very little cytoplasm formed during the uneven cytokinesis of oogenesis that does not become a functional gamete and usually degenerates.

Seminiferous Tubules

A network of tubules within the testes where sperm cells develop.

Sertoli Cells

Supporting cells lining the seminiferous tubules that provide nutrients and secrete signaling molecules to support sperm production.

Leydig Cells

Cells located adjacent to seminiferous tubules in the testes that produce androgen hormones, primarily testosterone.

Spermatogonia

Diploids stem cells in the gonads that divide mitotically to self-renew or differentiate into primary spermatocytes.

Primary Spermatocytes

Diploid male germ cells that undergo meiosis I to yield two haploid secondary spermatocytes.

Secondary Spermatocytes

Haploid male germ cells produced from meiosis I that undergo meiosis II to form immature spermatids.

Spermatids

The four haploid, non-motile cells produced at the end of meiosis II during male gametogenesis.

Syncytium

A structure formed by cytoplasmic bridges interconnecting developing male germ cells during incomplete cytokinesis, allowing synchronous cell maturation.

Spermiogenesis

The final stage of spermatogenesis during which haploid spermatids shed excess cytoplasm and form specialized anatomical structures like tails and acrosomes to become spermatozoa.

GnRH

Gonadotropin-releasing hormone; secreted by the hypothalamus to stimulate the anterior pituitary gland to produce FSH and LH.

FSH

Follicle-stimulating hormone; released by the anterior pituitary to stimulate Sertoli cells in males and ovarian follicle growth in females.

LH

Luteinizing hormone; released by the anterior pituitary to stimulate testosterone secretion by Leydig cells in males and trigger ovulation in females.

Corpus Luteum

An endocrine structure formed from the ruptured follicle following ovulation that secretes progesterone to thicken the uterine endometrium.