Exercise 1 solution

from itertools import product
from fractions import Fraction

def dominant_fraction(n):
    gam = list(product("Aa", repeat=n))
    total = 0
    hits = 0
    for g1 in gam:
        for g2 in gam:
            total += 1
            if all("A" in (x, y) for x, y in zip(g1, g2)):
                hits += 1
    return hits, total

for n in (1, 2, 3):
    h, t = dominant_fraction(n)
    print(n, h, t, Fraction(h, t), Fraction(3, 4) ** n == Fraction(h, t))

Output:

1 3 4 3/4 True
2 9 16 9/16 True
3 27 64 27/64 True

Reading it: every gamete of an all-heterozygous parent is a choice of A or a for each gene. A child shows the dominant form of every gene only if at least one of its two gametes carries A at each position, and counting those cases gives (3/4) to the power n.