Bert has blonde hair (b). Molly has brown hair (B), but her genotype is Bb, meaning she carries a recessive blonde allele. What is the likelihood of Bert and Molly's second child having brown hair?

50%

Explanation:

Iif you do a punnet square you get Bb, Bb, bb, and bb

since blond is represneted by the recessive bb it's a 50% the child will have blond hair

the unequal cytoplasmic division that  results  in  one egg  and three polar bodies ensures that a fertilized  egg has  ample nutrients  forits journey  to  the uterus.