Fertilization and Early Development (Video notes)

Vocabulary flashcards covering fertilization concepts from the lecture notes.

Fertilization

Formation of a diploid zygote from haploid egg and sperm; involves recognition at a distance, contact recognition and binding, egg and sperm fusion, blocks to polyspermy, and egg activation.

Zygote

Diploid cell formed when haploid egg and sperm unite during fertilization.

Resact

Soluble glycoprotein from the sea urchin egg jelly layer that guides sperm by chemotaxis toward higher concentrations; species-specific.

Chemotaxis

Migration of cells toward a chemical gradient; in sea urchin, movement toward resact.

Recognition at a distance

Initial sperm-egg interaction where chemical cues guide sperm toward the egg before contact.

Recognition at contact

Binding between sperm and egg mediated by surface molecules; in sea urchin, jelly coat components and receptors.

Jelly coat

Outer egg layer containing molecules that participate in sperm recognition (e.g., resact, fucose sulfate).

Fucose sulfate

Carbohydrate in the sea urchin jelly layer that binds to a receptor on the sperm for contact recognition.

Sperm plasma membrane receptor

Receptors on the sperm surface that bind egg jelly layer components during recognition.

Acrosomal reaction

Release of hydrolytic enzymes from the acrosome; formation of the acrosomal process that penetrates the jelly coat and binds to egg receptors.

Acrosomal process

Actin-rich projection formed during the acrosomal reaction that penetrates the jelly coat and contacts egg receptors.

Bindin

Sperm acrosomal protein that binds specifically to the egg’s vitelline layer, enabling species-specific fertilization.

Vitelline layer

Egg envelope just outside the egg plasma membrane that binds the acrosomal process during sea urchin fertilization.

Fast block to polyspermy

Rapid depolarization of the egg plasma membrane after sperm-egg fusion, preventing additional sperm from fusing.

Depolarization

Change in membrane potential making the inside of the egg more positive; part of the fast block to polyspermy.

Cortical reaction

Fusion of cortical granules with the egg plasma membrane releasing enzymes that modify the fertilization apparatus and form the fertilization envelope.

Cortical granules

Vesicles in the egg that release enzymes and other molecules to modify the vitelline layer and harden the fertilization envelope.

Fertilization envelope

Hard, extracellular layer formed after cortical granule release that blocks polyspermy.

Slow block to polyspermy

Permanent barrier to additional sperm created by cortical reaction and changes to the egg’s extracellular layers.

Zona pellucida

Extracellular matrix surrounding the mammalian oocyte; composed of ZP1, ZP2, ZP3; receptors on sperm bind ZP3.

ZP3

Zona pellucida glycoprotein that binds sperm receptors to initiate fertilization; mediates sperm binding.

ZP1 and ZP2

Zona pellucida glycoproteins contributing to the structure of the zona pellucida.

Zona pellucida receptors

Sperm surface receptors that bind to ZP3 on the zona pellucida to initiate acrosomal reaction in mammals.

Sperm capacitation

Process by which the sperm’s glycoprotein coat and seminal proteins are removed in the female tract, increasing metabolism and motility; triggered by bicarbonate.

Microvilli

Projections on the egg plasma membrane that help facilitate sperm fusion in mammals.

Calcium influx

Rise in intracellular calcium in the egg that triggers cortical granule fusion and other activation events.

Polar body

Small cell produced during meiosis that is extruded; in mammals, the second meiotic division yields a polar body.

Second meiotic division

Completion of meiosis II after fertilization, producing the haploid ovum and a polar body.

Egg activation

Early events (increased metabolism) and late events (initiation of protein and DNA synthesis) that prepare the zygote for cleavage.

First cell division

Initial mitotic division of the zygote after fertilization; timing: sea urchin ~90 minutes; humans ~12–36 hours.