Question

It shows the possibility of having either a male child, XY, or a female child, XX. The Gordon family has four boys. Mr. and Mrs. Gordon are hoping for a girl. What is the probability that the next child will be a girl?
A 1:4 or 25%
B 2:4 or 50%
C 3:4 or 75%
D 4:4 or 100%
Part B
Pea plants were used by Gregor Mendel in the first genetic crosses that enabled him to formulate the laws of inheritance and genetic probability. Consider the Punnett square for pea seed shape and color.



What is the probability that round peas will be produced, regardless of color?
A 0.50 or 50%
B 0.67 or 67%
C 0.75 or 75%
D 1.00 or 100%

Answer 1

Part A: B — 2/4 or 50%.
Each child's sex is an independent 50/50 event, so the next child has a 1/2 chance of being female.

Part B: C — 0.75 or 75%.
With a typical cross of heterozygous parents (Rr x Rr for seed shape), 3 out of 4 offspring show the dominant round phenotype. If considering both shape and color (RrYy x RrYy), the Punnett-square phenotypic ratio gives 12 round out of 16 total = 75%.