Answer:
Dichotomous key refers to a utility that allows the classification of living organisms to help you identify specific traits/characteristics of a specific non-living or living being.
We purposefully crossbreed certain individuals with the traits or the alleles for the traits within a species in hopes that the offspring exhibit these desires traits
The newly fertilized egg gains mass only after it is implanted in the uterus wall. Before the implantation, there is no gain in the mass of the fertilized egg. Moreover, the nourishment is not derived from the cell of the uterus. A newly fertilized egg is capable of surviving without the nourishment from mother as long as the nourishment is provided in vitro. Hence, the statements of Nina and Carole are not right.
Hence, the answer is 'the statement of Sarah is correct'.
We can divide this question to two parts: Yy and TT. First, the parents have Yy(1) and Yy(2). The offspring may have four types: Y1Y2, Y1y2, Y2y1, y1y2. So the probability of getting Yy is 1/2. The same, the probability of getting TT is 1/4. So the final probability of YyTT is (1/2)*(1/4)=1/8
