7. In the year 2213, earth will be taken over by aliens.  The leader of the aliens will force certain humans to procreate in an attempt to create a “perfect” human while also giving the aliens’ underpaid geneticists an opportunity to test Mendel’s laws.  Big-mouthed and small-mouthed humans were crossed in different combinations.  It is unknown which phenotype is dominant. The genotypes of the individuals are also unknown.

For parts a through d, if possible, determine which phenotype is dominant and the genotype of each individual.  If there are multiple possibilities, list them all.

Note: the genetic control of mouth size may be different for each of the four crosses!

(a) Big mouth x small mouth.  All 51 progeny have big mouths.

(b) Big mouth x small mouth. Progeny segregate 24 big mouths to 27 small mouths.

(c) Small mouth x small mouth. Progeny segregate 12 big mouths to 35 small mouths.

(d) Big mouth x big mouth.  All progeny have big mouths.

(ii) If the progeny from cross d are then crossed with small-mouthed individuals, all the resulting progeny have big mouths.  Can you now determine which phenotype (for part d) is dominant and what are the genotypes of the original parents in cross d?