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Multiple Choice
It is far more common to find human genetic disease caused by __________ alleles than by __________ alleles because __________.
A
dominant; recessive; dominant alleles have an evolutionary advantage over recessive alleles
B
dominant; recessive; dominant alleles became dominant because they aid the survival of the organism carrying them
C
recessive; dominant; even when homozygous, recessive alleles usually do not cause as much damage as dominant alleles
D
None of the listed responses is correct.
E
recessive; dominant; harmful recessive alleles can survive in the heterozygote without any selection pressure against them
Verified step by step guidance
1
Understand the difference between dominant and recessive alleles. Dominant alleles express their traits even if only one copy is present, while recessive alleles require two copies to express their traits.
Consider how genetic diseases are passed on. Recessive alleles can be carried by individuals without expressing the disease, allowing them to be passed on to offspring without being selected against.
Recognize that harmful recessive alleles can persist in a population because they can be carried by heterozygotes, who do not express the disease phenotype.
Dominant alleles, if harmful, are more likely to be selected against because they express the disease phenotype even in heterozygotes, reducing the likelihood of being passed on.
Conclude that recessive alleles are more common in genetic diseases because they can 'hide' in carriers, whereas dominant alleles are often eliminated if they are harmful.