The Odds of Being You: A zoomonster from planet Planktonia
You should have a sense now that the basic principles of heredity can result in a diverse number of phenotypes. If you performed the coin toss project over and over, your zoomonster babies would probably all be different in some way. Similarly, you are different from your siblings and your parents are different from their siblings.
In step 5 of the procedure, you made punnett squares for 4 traits to determine the possible offspring phenotypes. You used the homozygous genotype when the trait was dominant. What did you notice about the offspring that resulted from each pairing? You may have noticed that when one parent has the homozygous dominant genotype for a trait, and the other parent has the recessive trait, the offspring will always have the dominant trait.
Given the information provided in the background section about the 23rd pair of chromosomes in humans, which parent determines the sex of a baby?
The father determines the sex of the baby since he can donate an X or Y chromosome, while the mother can only donate an X chromosome.
What is the probability of having a male baby?
Because it is equally likely that the father will donate an X or Y, the probability of having a male baby is ? or 0.5.
What is the probability of having a female baby?
We know the two probabilities of having a male or female are equal, so the probability of having a female is 0.5. The question can also be approached using the following reasoning. When there are only two outcomes, the individual probabilities of each outcome must sum/add-up to 1. Since the probability of having a male baby is .5, the probability of having a female baby is 1-0.5 = 0.5.
Use your imagination to design your own creatures for breeding experiments. First, pick the planet you will travel to. Next, pick 5 traits for the creature and determine the dominant and recessive phenotype for each trait. Set your table up the same way it was set up for the zoomonsters from Planktonia (see Table 1). Perform five coin tosses, one for each trait, and keep track of your outcomes (ie, heads or tails, dominant or recessive). Draw your creature! Finally, determine the genotypes of each phenotype in your table. Set your genotype table up like table 2. Remember, you can pick any letter of the alphabet to represent the genotype for a given trait, but the dominant form will have the capital letter, while the recessive form will have the lower-case letter. There will be two possible genotypes for each dominant trait. Finished? Excellent work!