Question

aubrey and ava are identical twins who were raised in separate homes by their divorced parents. now, as they enter elementary school, aubrey shows mild symptoms of phenylketonuria (pku), but avas symptoms are more severe. what do the girls have different for this disease?
a. autosomes
b. alleles
c. phenotypes
d. genotypes

Explanation:

• Autosomes: These are non - sex chromosomes. Since the twins are identical (same genetic makeup in terms of chromosomes), this is not the difference.
• Alleles: Identical twins have the same alleles for a particular gene (assuming no new mutations).
• Phenotypes: Phenotype is the observable expression of a genotype. Identical twins (same genotype) can have different phenotypes due to environmental factors. In this case, they were raised in different environments (separate homes), which could lead to different severity of symptoms (a phenotypic difference) for the same genetic disorder (PKU).
• Genotypes: Identical twins have the same genotype (except for possible new mutations which are not indicated here).

Answer:

C. phenotypes