Some people have freckles, and some people do not have freckles. If a child has freckles, at least one parent has freckles. However, the child may have a sibling that does not have freckles. Which statement best describes the presence of freckles? a) Freckles are not determined by DNA. b) There are two alleles for freckles. c) There is no dominant allele for freckles. d) Freckles are determined by two genes instead of by one.

The correct answer is:  b) There are two alleles for freckles.

Explanation:

According to the question, it is said that, if a child has freckles then it is mandatory that either of his parents must have freckles. This indicates that the freckled character must be transmitted through genes or DNA (deoxyribonucleic acid) from the parents to the offspring and its occurrence is determined by heredity. Hence, option a) is incorrect.Also, it is said that the siblings of the freckled child does not have freckles. This means in a diploid organism having two sets of chromosomes (one from either parent) each character is determined by two variants of the same gene. These variants can be similar (homozygous) or dissimilar (heterozygous) and are called the Alleles. Hence, option b) is correct.Out of the two alleles, one is capable of expressing itself not only in homozygous condition but also in the presence of the allele (heterozygous condition). This is called the Dominant allele. The other allele gets suppressed in presence of the dominant allele and can express itself only in the homozygous condition. This is called the Recessive allele. Option c) is incorrect. This is because if no dominant allele would have existed for freckles then all the people would have developed freckles irrespective of whether they are homozygous or heterozygous for the freckled allele.Option d) is incorrect. This is because if freckles would have been determined by more than one genes it would have been expressed in all the offspring as all of them obtain the genes from either of the parents.

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