Some people have freckles, and some people do not have freckles. If a child has freckles, at least one parent has freckles. Howe
ver, the child may have a sibling that does not have freckles. Which statement best describes the presence of freckles? 1.Freckles are not determined by DNA. 2.There are two alleles for freckles. 3.There is no dominant allele for freckles. 4.Freckles are determined by two genes instead of by one. If Mendel had crossed a true breeding dominant plant with a true breeding recessive plant, in which of the three generations is the recessive trait visible? 1.F1 generation 2.P generation 3.F1 generation and F2 generation 4.P generation and F2 generation.
2 answers:
Part 1.
The correct answer is option 2.There are two alleles for freckles.
According to the condition of the occurrence of the freckles, it can be concluded that the freckle is an autosomal dominant condition. The freckle can only be inherited, if there is at least one dominant allele in any of the parent. If both the individuals are heterozygous for the trait, they can produce an offspring without freckle by passing down the recessive alleles to the progeny. So, the freckles are controlled by two alleles, which can be either dominant or recessive.
Part 2.
The correct answer is option 4. P generation and F2 generation.
In this case, it is given that true bred homozygous recessive plant is crossed with true bred homozygous dominant plant. The true bred recessive plant always shows the recessive phenotype. When true bred homozygous recessive plant is crossed with true bred homozygous dominant plant, the F1 generation would produce all the heterozygous individual and exhibit dominant phenotype. When the F1 generation is self crossed, it result in 75% dominant phenotype and 25% recessive phenotype.
A possible cross for this case is given in the picture.
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