ZZ-ZW SEX DETERMINATION

The female is heterogametic, and the male is homogametic. The ZZ-ZW system is found in birds, some reptiles, butterflies, some amphibians, and some fishes. 

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#Id: 4745

#Unit 5. Developmental Biology

PKC-3 restricts PAR-1 and PAR-2 to the internal cytoplasm by phosphorylating them.

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#Id: 4746

#Unit 5. Developmental Biology

Sperm microtubules contacts the cortical cytoplasm and initiates cytoplasmic movements that push the male pronucleus to the nearest end of the oblong oocyte.

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#Id: 4747

#Unit 5. Developmental Biology

Sperm microtubules protect PAR-2 protein from phosphorylation, allowing it to enter the cortex along with its binding partner, PAR-1.

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#Id: 4748

#Unit 5. Developmental Biology

Once PAR-1 is in the cortical cytoplasm, it phosphorylates PAR-3 causing PAR-3 and its binding partners PAR-6 and PKC-3 to leave the cortex.

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#Id: 4749

#Unit 5. Developmental Biology

At the same time, the sperm microtubules induce the contraction of the actin-myosin cytoskeleton toward the anterior, thereby clearing PAR-3, PAR-6, and PKC-3 from the posterior of the 1-cell embryo.

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#Id: 4750

#Unit 5. Developmental Biology

During first cleavage, the metaphase plate is closer to the posterior, & fertilized egg is divided into two cells:

one having the anterior PARs (PAR-6 and PAR-3)

one having the posterior PARs (PAR-2 and PAR-1)