genetics and your mother

remember the passage about phenotype being determined by the mother? what did everyone put for these questions-
1. why does the larvae have brown eyes and then red at adulthood? i put that the pigment k-something is in the oocyte.
2. what happens when brown males and brown females mate? well the problem is that it wasnt clear whether this was a BB x Bb or Bb x Bb or Bb x BB cross. I assumed it was Bb x Bb...as this created a perfect answer choice. Of course, all larvae are brown initially (since the mom is). If it was Bb x Bb...1/4th will be red in adulthood. If its BB x Bb or Bb x BB, 1/2 will be red in adulthood.

 

oh. of course. mental lapse there. so yeah. all red->1/4 brown.

 

I think its b/c the larvae have pigments from the mothers egg. when these run out, the larvae (which is an adult now) loses pigment, unless it has the gene. so the larvae run out of mother's pigment and dont produce anymore b/c they lack the B gene. its hard to say which is a better way of answering this question. they lose pigmentation b/c the pigments fr mom run out, but also b/c they cannot produce more (lack B gene). I guess if u think of it one way (as in asking why they LOSE pigmentation) its b/c mom's runs out. if you think of it as asking why they don't have pigmentation (its b/c they dont have the B gene).

 

it did say the color gets used up. but still, i see that it can be interpretted 2 different ways. colors there = brown larvae. gets used up = red, unless you have the B allele and can produce the pigment urself. so as to why the color changes from red to brown, i can see that either (a) k-pigment from maternal oocyte gets used up and (b) the offspring lacks the B allele BOTH seem right. in fact, it gets used up AND the offspring lacks the B allele.

just having it get used up isn't enough, as even when the mothers pigments are used up, 1/2 of the offspring from Bb (female) x bb (male) cross retain the brown pigment.

however, just "not having the B" allele isn't enough. as in the bb (female) x Bb (male) cross, the offsprings lacking the b allele (bb offspring) do not see a pigment change from brown to red. instead, these offspring start out as red.