Fertilization (incomplete this shi boring af) Flashcards
what is isogamy
sexual reproduction by the fusion of similar gametes
what is ansiogamy
sexual reproduction by the fusion of different gametes. anisogamy has evolved independently across most multicellular organisms
how many polar bodies are produced during oogenesis in humans
2 polar bodies are formed during the second stage of meiosis, one for each devision
what are the two types of cell lineages after fertilisation
somatic and germ cells
how are primordial get cells formed
they are either induced by BMP signalling (like in humans). Alternatively the oocytes can contain cytoplasmic determinants that are inherited into some cells
what is the zone pellucida
a thick extracellular coat that surrounds all mammalian oocytes.
- it protects the egg
-enables cell communication
-prevents polyspermy
eggs without this coating are infertile
what is chemotaxis
the chemical attraction between the sperm and the egg
how does a sperm bind to an egg cell and what happens when it does
the sperm cell releases enzymes to digest the egg membrane
sperm then binds to integrins on the egg surface
this triggers a fast change in the eggs surface potential and causes the exocytosis of cortical granolas to prevent polyspermy
what is the animal-vegetal axis
the axis where at one end is animal tissue (the embryo) and the other end is vegetal tissue (yolk) that will not form the embryo
what are the different distributions of egg yolk
Alecithal: little or no yolk
oligolecihtal: small but evenly distributed yolk
isolecithal: yolk that is evenly distributed throughout the cytoplasm
mesolecithal: moderate amount of unevenly distributed yolk
telocithal: large amount of yolk
what are the different cell cleavage patterns and where are they found
Holoblastic cleavage is when the cells divide the yolk completely: mammals and anphibians as well as echinoderms
Meroblastic cleavage: cleavage furrows are incomplete, found in fish and birds
Superficial cleavage: only the nuclei divide initially, found in insects
what are the different cell cleavage patterns as defined by the orientation of mitotic spindles
Radial and Rotational cleavage: mitotic spindles are along the egg axis (deuterostomes)
Spiral cleavage: mitotic spindles are at an oblique angle to the egg axis (annelids, molluscs and flatworms)
