Genes and Health: Mammalian Gametes and Fertilization

Vocabulary-style flashcards covering the cellular structure, specialized adaptations, and fertilization processes of mammalian sperm and egg cells as described in the Unit 2 Topic 3 lecture notes.

Acrosome

A specialized organelle in the sperm head containing hydrolytic enzymes, such as acrosin, used to break down the zona pellucida.

Zona Pellucida

A jelly-like protective layer surrounding the oocyte that forms the fertilization membrane to prevent polyspermy.

Cortical Granules

Vesicles containing enzymes that are released by exocytosis into the zona pellucida, cause it to harden, and create the fertilization membrane.

Mitochondria (in sperm)

Organelles located in the mid-piece that produce $ATP$ through aerobic respiration to provide energy for the movement of the flagellum.

Flagellum

The tail of the sperm that produces whip-like movements to propel the cell through the female reproductive tract.

Corona Radiata (Follicle Cells)

A protective coating consisting of follicle cells that surround the secondary oocyte.

Haploid Nucleus

A nucleus containing highly condensed chromosomes ($23$ in humans) to restore the diploid number ($46$) upon fusion during fertilization.

Capacitation

Processes occurring in the female reproductive tract that make the sperm membrane more fluid by removing surface proteins and cholesterol, increasing motility (hyperactivation).

Acrosome Reaction

The process where sperm bind to receptors on the zona pellucida, causing the acrosome to swell and rupture, releasing acrosin to digest a path to the egg cell membrane.

Cortical Reaction

The release of calcium ions inside the egg following membrane fusion, triggering cortical granules to fuse with the cell membrane and harden the zona pellucida.

Polyspermy

The entry of more than one sperm cell into a single egg cell, prevented by cell membrane depolarization and the hardening of the zona pellucida.

Zygote

The diploid cell formed by the fusion of male and female gamete nuclei, containing a full set of $46$ chromosomes.

Cytoplasm (Egg Cell)

A large region containing food reserves and nutrients for the growth of the developing embryo, measuring approximately $100\,\mu\text{m}$.

Spermatogenesis

The process of male gamete formation originating from germinal epithelial cells and transitioning through spermatogonia, primary, and secondary spermatocytes.

Oogenesis

The process of female gamete formation that involves the production of a secondary oocyte and polar bodies from oogonia and primary oocytes.

Spermatozoa (Characteristics)

Defined by the phrase 'Many, Mini, Motile', these cells are streamlined for easy movement and are approximately $50\,\mu\text{m}$ in length.

Secondary Oocyte (Characteristics)

Defined by the phrase 'Few, Fat, Fixed', these cells have no independent motility and are moved by cilia in the oviduct.

Genetically Variable Gametes

A source of genetic variation in offspring produced during meiosis; their random fusion during fertilization further increases diversity.