This biology question covers important biological concepts and processes. The step-by-step explanation below helps you understand the underlying mechanisms and reasoning.

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Both parents are normal but have affected children, meaning they must both carry the recessive allele.
Here are the solutions for the pedigree diagram:
2.1 Step 1: Observe the phenotypes of the parents. Both the Father (unshaded square) and the Mother (unshaded circle) are normal. Step 2: Observe the phenotypes of their children. They have an affected daughter (shaded circle) and an affected son (shaded square). Step 3: Since the genetic disorder is controlled by a recessive allele (), affected individuals must have the genotype . Step 4: For the affected children () to inherit two recessive alleles, they must receive one allele from the Father and one allele from the Mother. Step 5: Since both parents are phenotypically normal, they must possess at least one dominant allele (). Step 6: Therefore, both parents must carry the recessive allele () while also having the dominant allele (), making their genotype heterozygous ().
2.2 Step 1: From 2.1, we know both parents are heterozygous (). Step 2: Perform a genetic cross between two heterozygous parents: . Step 3: The possible genotypes for the offspring are , , and . Step 4: Normal children are those who do not express the recessive disorder. Their genotypes can be homozygous dominant () or heterozygous (). The possible genotype(s) of the normal children are:
2.3 Step 1: Identify the parents and their children in the pedigree. The Father and Mother are normal. Step 2: Observe their first child, who is an affected female (shaded circle). Step 3: If the characteristic were sex-linked (specifically X-linked recessive, as most sex-linked disorders are), an affected female would have the genotype . Step 4: For a female to have the genotype , she must inherit one allele from her mother and one allele from her father. Step 5: However, the Father in the pedigree is normal (unshaded square). If the characteristic were X-linked recessive, a normal father would have the genotype . He would pass his allele to all his daughters. Step 6: Since a normal father () cannot have an affected daughter (), the characteristic cannot be sex-linked.
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2.1 Step 1: Observe the phenotypes of the parents. Both the Father (unshaded square) and the Mother (unshaded circle) are normal.
This biology question covers important biological concepts and processes. The step-by-step explanation below helps you understand the underlying mechanisms and reasoning.