Multiple Choice
In a pedigree chart, which symbol is typically used to represent an affected female?
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2. Mendel's Laws of Inheritance
Pedigrees
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Which of the following observations from a pedigree most strongly suggests that a disorder is autosomal recessive?
A
The disorder appears in offspring of unaffected parents and affects both males and females equally.
B
The disorder is present in every generation and affects only males.
C
Affected individuals always have at least one affected parent.
D
The disorder is transmitted from affected fathers to all their daughters but not to their sons.
Verified step by step guidance1
Understand the key characteristics of autosomal recessive inheritance: the disorder typically appears in offspring of unaffected parents (carriers), and it affects males and females equally because the gene is located on an autosome, not a sex chromosome.
Analyze the observation that the disorder appears in offspring of unaffected parents. This suggests that both parents are carriers (heterozygous) and the affected offspring are homozygous recessive, which is a hallmark of autosomal recessive inheritance.
Consider the fact that the disorder affects both males and females equally. This indicates that the gene is not sex-linked, supporting the idea that it is autosomal.
Compare this to other inheritance patterns: if the disorder were dominant, it would appear in every generation and affected individuals would have at least one affected parent; if it were X-linked recessive, it would affect males more frequently and show different transmission patterns.
Conclude that the observation 'the disorder appears in offspring of unaffected parents and affects both males and females equally' most strongly suggests autosomal recessive inheritance.
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