# Punnett Squares Lab Report

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The independent variable and dependent variable for steps four and five are the opposite of steps one through three. After identifying the variables a hypothesis is to be conducted, and the hypothesis states, “ If either parent mouse passes a dominant allele, the offspring will have black fur.” Having this hypothesis allows us to begin the experiment and come to the conclusion as to whether or not the results will either support or refute the hypothesis. For the first part of the experiment students are to predict and confirm the offspring of two mice homozygous for black fur. Now, in order to proceed identifying an unfamiliar term is key. Homozygous refers to having the same or identical alleles. With this in mind, students can deduce that both the male and female have BB as their genotypes since it is given to us that their fur is black, and black is the dominant trait. This means when both BB’s are put into the Punnett square the results of the offspring are all BB’s. At this point students now have all the information needed to fill in the “predicted percentage” portion of the phenotype Punnett Square. The percentage for the black fur is 100% and white fur is

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This means that ¾ of the offspring have black fur, while the other ¼ are white. At this point students now have all the information needed to fill in the “predicted percentage” portion of the phenotype Punnett Square. The percentage for the black fur is 75% and white fur is 25%. Next, students are to breed a litter of ten mice in the simulation. 8 out of 10 should be black and 2 out of 10 should be white, therefore the simulated percentage is 80% for black fur and 20% for white fur. Concluding that the Punnett Square predicted 75% of the mice would be black, but the actual percentage was not too far off being at 80%! For the last parts of the lab experiment students are to work backwards, which means finding the phenotype of the offspring to in order to find the genotype of the parents. Students are given the number of mice that have black fur (5/10) and those that have white fur (5/10). Given this number, students can convert the given fractions into percentages, which is 50% for each fur color. Now, in order to find the genotype for the offspring we have to keep in mind that the outcome for the offspring should be a ratio of 50:50. Different combinations can result in a 50:50 offspring, but my result consisted of the genotype of the female being bb, while the genotype for the male is