If the unknown mouse mates with the pure white mouse and any white offspring are observed, then the unknown mo?

**Cross between a heterozygous mouse (Ff) and a pure breed white mouse (ff) (pure recessive and heterozygous crosses).**

1.) When a homozygous, or pure breeding, white mouse is crossed with a heterozygous black mouse, what is the expected Black:White ratio in the offspring?

2.) When a homozygous, or pure breeding, white mouse is crossed with a homozygous black mouse, what is the expected Black :White ratio in the offspring?

3.) The parents in both of the crosses look the same. Why are the results different?

~As black is the dominant gene, there has to be no black present in a mouse for it to be white. If a pure black mouse is used for breeding, all the offspring will be black in color, even if the other mouse was a pure white mouse

~As black is the dominant gene, there has to be no white present in a mouse for it to be black. If a pure white mouse is used for breeding, all the offspring will be white in color, even if the other mouse was a pure black mouse

~There is no dominant gene, so it is impossible to tell exactly what you are going to get. This is the reason that you use probability to inferer what is "suppose" to happen.

~Since white is the dominant gene, there has to be no white present in a mouse for it to be black. If a pure white mouse is used for breeding, all the offspring will be white in color, even if the other mouse was a pure black mouse

4.) How can a pure white mouse help determine the genotype of a black mouse?

~A white mouse is purely recessive, and cannot produce black offspring if the other mouse contributes a black gene. But if the gene provided by the other mouse is also recessive, or the white gene, a white offspring will be seen. If the unknown mouse mates with the pure white mouse and any white offspring are observed, then the unknown mouse has a heterozygous genotype. Otherwise it is probably a pure black mouse

~A black mouse is purely recessive, and cannot produce black offspring if the other mouse contributes a black gene. But if the gene provided by the other mouse is also recessive, or the white gene, a white offspring will be seen. If the unknown mouse mates with the pure white mouse and any white offspring are observed, then the unknown mouse has a heterozygous genotype. Otherwise it is probably a pure black mouse

~A black mouse is purely recessive, and will produce white offspring if the other mouse contributes a white gene. But if the gene provided by the other mouse is also recessive, or the black gene, a black offspring will be seen. If the unknown mouse mates with the pure black mouse and any black offspring are observed, then the unknown mouse has a heterozygous genotype. Otherwise it is probably a pure white mouse

~A white mouse is purely recessive, and will produce black offspring if the other mouse contributes a black gene. But if the gene provided by the other mouse is also recessive, or the white gene, a white offspring will be seen. If the unknown mouse mates with the pure white mouse and any white offspring are observed, then the unknown mouse has a heterozygous genotype. Otherwise it is probably a pure black mouse

1 Answer

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  • Anonymous
    9 years ago
    Favorite Answer

    1. The gametes of the heterozygous one are f and F from the homozygous one f. So the first generation would have ff or Ff genotypes. So half black half white as white is recessive. So the ratio is 1:1 black:white.

    2. The gametes are F from the black mouse and f from the white. So the F1 would be Ff genotype. Which is all black Phenotype. So the ratio is 1 black 0 white, or 100 per cent black.

    3. The first one.

    4.The last one

    Source(s): High school biology in Greece
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