Coin Sex Lab Relate and Review

         In this lab we looked at how the probability of having a child with a certain trait was related to actually predicting how many children would actually have that trait. In order to illustrate how genes separate during meiosis, we used coins as props. We determined what possible genotypes we had by looking at our phenotypes; for example if a person had a phenotype of brown hair their genotype could be either BB (homozygous dominant) or Bb. One each side of the coin we wrote one allele (if an individual was heterozygous for brown hair they would write "B" on one side of the coin and "b" on the other.) When we dropped the coins onto the table, it was random which allele landed face side up. This is a simulation of meiosis. When we subsequently paired our coin with our partner's coin to find out the offspring's genotype, we simulated sexual recombination.
         We did a dihybrid cross--we looked at the gene for having brown vs. blonde hair, and the gene for having brown vs. eyes at the same time. We crossed two individuals who were double heterozygous. Their genotypes were BbEe (B=brown hair, b=blonde hair, E=brown eyes, e=blue eyes). The expected phenotypic ratio was 9 brown hair brown eyes: 3 brown hair blue eyes: 3 blonde hair brown eyes: 1 blonde hair blue eyes. Our results were 8 brown hair brown eyes: 3 brown hair blue eyes: 4 blonde hair brown eyes: 1 blonde hair blue eyes. Probability says how likely something is to happen, but the certainty of something actually happening is different. Our results were close to the expected, but slightly different.

Probability is a prediction of the likelihood of an event occurring. If thousands of trials were to be done, the law of averages would ensure that the probability of getting a certain trait was met. However, if a person were to flip a coin 5 times, it is entirely possible that they could flip 10 heads in a row, even though the probability of flipping a head is 50%. Most humans don't have that many offspring compared to other species, and often times probability is inaccurate in predicting offspring's traits.

Genetics can be seen everywhere in our life. Genes are the reason why people have certain traits and the reason why people look the way that they do. I have wondered in the past why some children have completely different traits, such as blonde hair or blue eyes (autosomal inheritance), than their parents do. Now, with the knowledge of punnett squares and different alleles, I can answer that question. Also, knowing how X-linked inheritance works, I can understand why certain people I know are colorblind, even if neither of their parents are.