L22: Fertilization and Sex Determination in Mammals

Imprinting

Heritable epigenetic control of gene expression.

Polyspermy

Condition of multiple sperm fertilizing one egg.

Totipotency

Ability of a cell to differentiate into any cell type.

Oocyte

Female germ cell involved in reproduction.

Acrosome

Cap-like structure on sperm containing enzymes.

Zona Pellucida

Clear outer layer surrounding the oocyte.

Sperm Izumo protein

Protein that binds to oocyte Juno for fusion.

Juno protein

Oocyte protein that interacts with sperm Izumo.

Meiosis II

Second meiotic division completed after fertilization.

Cortical granules

Oocyte structures that prevent polyspermy post-fertilization.

Ovastacin

Enzyme that digests zona proteins to prevent polyspermy.

SRY gene

Sex-determining region of the Y chromosome.

Klinefelter syndrome

Condition of males with extra X chromosomes (XXY).

Turner syndrome

Condition of females with a single X chromosome (X0).

Sertoli cells

Cells essential for testes formation.

Sox9

Gene induced by SRY for male development.

Fgf9

Gene that represses female development signals.

Wnt4

Gene that promotes female development.

Testosterone

Hormone produced by testes for male development.

Müllerian ducts

Structures that develop into female reproductive organs.

Wolffian ducts

Structures that develop into male reproductive organs.

Müllerian inhibiting substance

Substance secreted by Sertoli cells to degrade Müllerian ducts.

Germ cells

Cells that give rise to gametes (sperm and eggs).

Retinoic acid (RA)

Signal that induces meiosis in female germ cells.

Cyp26b1

Protein that degrades retinoic acid in male germ cells.

Barr body

Inactivated X chromosome in female mammals.

Xist RNA

RNA that induces X chromosome inactivation.

Dosage compensation

Equalization of gene expression from sex chromosomes.

Epigenetic changes

Modifications that affect gene expression without altering DNA.

Histone methylation

Modification affecting chromatin structure and gene expression.

Histone acetylation

Modification that generally promotes gene expression.

Prophase of meiosis I

Stage where vertebrate oocytes arrest development.

Sperm nucleus fusion

Process where sperm nucleus combines with oocyte nucleus.

Intracellular Ca++ release

Trigger for zygote activation post-fertilization.

Sperm centrioles

Structures used for first zygote division.

Sex reversal

Condition where chromosomal sex does not match phenotype.

Primordial germ cells

Early cells that develop into gametes.

Mosaic X inactivation

Random inactivation of one X chromosome in females.

Calico cats

Example of mosaicism due to X-linked genes.

Epigenetic control

Regulation of gene expression through chemical modifications.

Fertilization process

Multistep interaction between sperm and egg.

Hyaluroidinase

Enzyme that digests hyaluronic acid in cumulus layer.

Acrosome reaction

Release of enzymes to penetrate the zona pellucida.

Sperm binding

Initial interaction of sperm with zona pellucida.

Meiosis timing

Differential timing of meiosis in male and female germ cells.