Teresa wrote:What would happen if two whites mated? would all the babies be white?
Since white pigmentation seems to be a recessive trait only those that are homozygous express it; therefore, 100% of the offspring from a cross of white monarchs would be white. Take a look at the table at
and replace the heterozygous (Oo) parents with homozygous (oo) ones - this should help you visualize what's going on.
You can liken the white form of the monarch to the classic (though somewhat oversimplified) genetic example of blue eyes in humans...simply speaking, blue eye color is recessive (represented by a lowercase "b") and brown is dominant (represented by an uppercase "B") so individuals can be described as:
BB = homozygous dominant (genotype) = brown-eyed (phenotype)
Bb = heterozygous dominant = brown-eyed
bb = homozygous recessive = blue-eyed
Using the simple 2x2 table referenced above, you can illustrate the following crosses:
BB x BB = 4BB (genotype) or 100% brown-eyed (phenotype)
Bb x Bb = 1BB:2Bb:1bb or 75% brown-eyed & 25% blue-eyed
bb x bb = 4bb or 100% blue-eyed
QUIZ: Can you figure out which crosses I left out and what the expected resulting progeny ratios would be?
As you can see, two brown-eyed parents can have blue-eyed children, but two blue-eyed parents cannot have a brown-eyed child; similarly, two orange monarchs may mate and give rise to white offspring, but matings between two white monarchs cannot result in orange offspring. Make sense?! Ok, class dismissed.