I posted the following comment on Boaphile's blog post about a possibly parthenogenetic boa litter. Parthenogenesis is so cool! Figured it would be worth posting again over here with a diagram for anyone interested.
Three possible ways a female could produce viable offspring without a male in the ZW/ZZ chromosome system:
1. Meiosis occurs normally, haploid gametes undergo terminal fusion resulting in either WW or ZZ (offspring inheriting two copies of 1/2 of the mother's genome). Since WW is non-viable, all offspring will be male and obviously not clones of mom (documented in birds and Varanids).
2. Meiosis occurs normally, haploid gametes undergo central fusion, resulting in ZW. All offspring will therefore be female, and even though they inherit the complete maternal genome, they will not be exact copies of the mother due to "crossing over". Plausible in this case given two phenotypes (ghost and anerythristic) were expressed in the litter.
3. Pre-meiotic chromosomal doubling occurs so that the 4 resulting gametes would be diploid (instead of the usual haploid) and exact copies of the maternal genotype. The fact that the litter contained two phenotypes suggests this is not the case here.
I would be very interested to know what genetic tests are being conducted to investigate this (microsats? DNA-fingerprinting?)and how retained sperm was ruled out.
