Genetic Predictions: Offspring Ratio Calculation
What is the predicted ratio of offspring from a cross between a white mouse with red eyes and a black mouse with black eyes?
a) 1/4, 1/4, 1/4, 1/4
b) 1/16, 1/16, 1/16, 13/16
c) 1/8, 1/8, 1/8, 5/8
d) 1/2, 1/4, 1/8, 1/8
Answer:
The predicted ratio of offspring from a cross between a white mouse with red eyes (bb ee) and a black mouse with black eyes (Bb Ee) is: 1/16 black fur, black eyes; 1/16 black fur, red eyes; 1/16 white fur, black eyes; and 13/16 white fur, red eyes. Therefore, the correct option is B
The student's question involves predicting the genetic outcome of a cross between a white mouse with red eyes (bb ee) and a black mouse with black eyes (Bb Ee). These traits are determined by two separate genes, one for fur color and one for eye color. For fur color, B is dominant (black fur) and b is recessive (white fur). For eye color, E is dominant (black eyes) and e is recessive (red eyes). To determine the predicted ratio of offspring with each phenotype, we can set up a Punnett square using both genes.
The correct answer is option b) 1/16, 1/16, 1/16, 13/16, as the cross of BbEe with bbee will yield:
- 1/16 of the offspring with black fur and black eyes (BbEe)
- 1/16 of the offspring with black fur and red eyes (Bbee)
- 1/16 of the offspring with white fur and black eyes (bbEe)
- 13/16 of the offspring with white fur and red eyes (bbee)
This results from the combinations of alleles that can arise when the parents' genotypes are crossed, taking into account the laws of Mendelian inheritance.