Fertilization Flashcards
consists of a series of events, which begins with the contact of a sperm with the egg envelope and ends with the union of the male and female pronuclei.
Fertilization
The transformation of the ? has stripped the cell of
non-essential materials and produced a swiftly moving, flagellated sperm
spermatid
is not self propelled (in most species) and waits for the arrival of the sperm
egg
Most ? are covered by one or more protective envelopes
unfertilized eggs
Most unfertilized eggs are covered by one or more protective envelopes, the ? must penetrate these coverings before contacting the egg plasma membrane and fusing with it.
sperm
The contents of the sperm’s ? aid in penetrating the envelopes of unfertilized egg
acrosome
is a change in the electrical potential of the egg plasma membrane. This electrical response occurs within one second after sperm contact.
The first response (fast block to polyspermy)
Another response occurs about 40 sec later; an impenetrable, non-cellular fertilization membrane (fertilization envelope) is formed around the egg ( what is this mechanisms to block the entrance of further sperm? _
the slow block to polyspermy
After entering the egg cytoplasm, the sperm head changes shape and assumes the typical form of a nucleus (spherical with chromatin indistinct). The sperm nucleus is now called the ?. It moves toward the center of the egg.
male pronucleus
the eggs of some species like? having already completed meiosis when the sperm enters
sea urchin (Strongylocentrotus purpuratus)
the eggs of some species still have to complete meiosis
I and II like?
Ascaris ( Ascaris lumbricoides )
the eggs of other species still have to complete meiosis
I and II (Ascaris) or meiosis II only like?
Dog: Canis lupus familiaris
Cat: Felis catus
At the completion of meiosis the egg assembles a nuclear envelope around its chromosomes to form the?
female pronucleus
The fusion of the pronuclei completes fertilization and produces the?
zygote, the diploid, single-celled embryo
The process of fertilization starts with a collision between the oocyte and a spermatozoon and when their pronuclei have merged, the resulting diploid cell containing the genetic code for a new individual is contained in the?
zygote
