Albinism in humans is inherited as a simple recessive trait. For the following families, determine the genotypes of the parents and offspring. (When two alternative genotypes are possible, list both.)
A normal male and an albino female have six children, three normal and three albino.

검증된 단계별 안내

Step 1: Understand the inheritance pattern. Albinism is a recessive trait, meaning an individual must inherit two recessive alleles (aa) to express the condition. A normal phenotype can result from either a homozygous dominant (AA) or heterozygous (Aa) genotype.

Step 2: Analyze the parents' phenotypes. The male is normal, so his genotype could be either AA or Aa. The female is albino, so her genotype must be aa (homozygous recessive).

Step 3: Examine the offspring's phenotypes. The offspring include three normal and three albino children. For albino offspring to occur, both parents must contribute a recessive allele (a). This means the male parent must be heterozygous (Aa), as a homozygous dominant (AA) male could not produce albino offspring.

Step 4: Determine the possible genotypes of the offspring. A cross between a heterozygous male (Aa) and a homozygous recessive female (aa) results in a Punnett square with the following probabilities: 50% heterozygous normal (Aa) and 50% homozygous recessive albino (aa).

Step 5: Conclude the genotypes. The male parent is heterozygous (Aa), the female parent is homozygous recessive (aa), and the offspring are either heterozygous normal (Aa) or homozygous recessive albino (aa).

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주요 개념

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Recessive Traits

Recessive traits are characteristics that only manifest when an individual has two copies of the recessive allele. In the case of albinism, the trait is expressed only when an individual inherits two recessive alleles (aa). If an individual has at least one dominant allele (A), the dominant trait will be expressed, masking the recessive trait.

Genotype vs. Phenotype

Genotype refers to the genetic makeup of an individual, specifically the alleles they carry, while phenotype is the observable expression of those genes. For example, an individual with the genotype 'Aa' (heterozygous) will have a normal phenotype, whereas 'aa' (homozygous recessive) will exhibit albinism. Understanding this distinction is crucial for predicting offspring traits.

Punnett Squares

Punnett squares are a tool used in genetics to predict the probability of offspring genotypes based on the parental genotypes. By organizing the possible alleles from each parent, a Punnett square can help visualize the potential combinations and determine the likelihood of traits being expressed in the offspring, such as normal pigmentation or albinism in this scenario.

Albinism in humans is inherited as a simple recessive trait. For the following families, determine the genotypes of the parents and offspring. (When two alternative genotypes are possible, list both.) A normal male and an albino female have six children, three normal and three albino.