Question

write a simple one paragraph report on mouse genetics.
What is the effect of the genes of the parental mice on the fur color of the offspring mice?
If either parent mouse passes a dominant allele, the offspring will have black fur.
Independent Variable: genotype of parents
Dependent Variable: traits of offspring
Note: The variables will switch their roles (independent vs. dependent) in steps 4 and 5.
Lab Procedure
In each of steps 1 through 3 on the next page, you will cross a different female and male pair of
mice and examine the inheritance of fur color. Repeat the substeps below each time.
a)
b)
c)
d)
e)
f)
In the Punnett square, fill in the shaded boxes with the alleles of each parent. Use B for the dominant
allele (black fur) and b for the recessive allele (white fur).
Fill in the unshaded boxes of the Punnett square with all possible offspring genotypes.
Based on the genotypes, fill in the table to the right with the predicted percentage (0%, 25%, 50%,
75%, or 100%) of offspring for each phenotype, black or white fur.
Confirm your prediction by simulating ten offspring. You can simulate breeding using technology
In the data table, record the number (out of 10) and percentage (out of 100%) of each phenotype in
the rows “Simulated Number” and “Simulated Percentages.”
In the box labeled “Comparison Statement,” write a comparison of the predictions of the Punnett
square with the offspring you saw.

Answer 1

Mouse fur color is determined by two alleles: B (dominant, black fur) and b (recessive, white fur); if either parent contributes a B allele the offspring will be black. In this lab the independent variable is the genotype of the parents and the dependent variable is the offspring’s fur color (note that the variables will switch roles in steps 4 and 5). For each of three different crosses you will (a) write the parents’ genotypes using B and b, (b) draw a Punnett square and place the parents’ alleles along the edges, (c) fill the four offspring genotype boxes, (d) determine the predicted phenotype percentages (0, 25, 50, 75, or 100% black or white) from those genotypes (examples: BB×BB → 100% black; BB×bb → 100% black; Bb×Bb → 75% black/25% white; Bb×bb → 50% black/50% white; bb×bb → 100% white), (e) simulate ten offspring using the provided technology and record the number and percent of each phenotype, and (f) write a short comparison statement describing how the observed simulated results match or differ from the Punnett-square predictions.