When both alleles' effects are shown, there is said to be:

Correct Answer: A

Rationale: The correct answer is A: codominance. Codominance refers to a genetic scenario where both alleles in a gene pair are fully expressed, leading to a phenotype that displays traits from both alleles equally. This is distinct from incomplete dominance where the traits blend. Choices B, C, and D are incorrect. Preponderance does not specifically relate to the expression of alleles. Ascendance and concurrence do not describe the genetic concept of codominance where both alleles are fully expressed.

Correct Answer: B

Rationale: Individuals with Klinefelter syndrome have an extra X chromosome (XXY), leading to reduced production of testosterone, the primary male sex hormone. This deficiency can result in various physical and developmental characteristics associated with the syndrome. Estrogen levels may actually be relatively elevated due to the imbalance between testosterone and estrogen. Choices C and D are incorrect as adenine and thymine are nucleotide bases found in DNA and are not related to hormone production.

Correct Answer: D

Rationale: Matt is exhibiting symptoms typical of Huntington's disease (HD), a hereditary condition characterized by involuntary movements, cognitive impairment, and behavioral changes. The fact that Matt's father and grandfather had similar issues supports the genetic nature of the disease. Phenylketonuria (PKU) is a metabolic disorder that affects amino acid metabolism, not presenting with the symptoms described. Cystic fibrosis primarily affects the respiratory and digestive systems, not causing the neurological symptoms described. Turner syndrome is a genetic condition affecting females and is not associated with the symptoms described in the case of Matt.

Correct Answer: A

Rationale: The correct answer is A. Tay-Sachs disease is most commonly found among Jewish families of Eastern European descent. It is a fatal genetic disorder that affects the nervous system. Choice B is incorrect because Tay-Sachs disease does not involve excessive mucus production in the lungs and pancreas. Choice C is incorrect as it states that Tay-Sachs disease is most commonly found among Asian American families, which is inaccurate. Choice D is also incorrect because Tay-Sachs disease does not cause muscular dystrophy characterized by weakening of the muscles.

Correct Answer: B

Rationale: A sonogram, also known as an ultrasound, is a procedure that utilizes sound waves to generate images of a developing embryo or fetus. This imaging technique is commonly used in prenatal care to monitor fetal development and identify any potential abnormalities. Choices A, C, and D are incorrect because a phenotype refers to an individual's observable traits resulting from genetic and environmental influences, a genotype is an individual's genetic makeup, and an alpha-fetoprotein (AFP) assay is a blood test used to screen for certain birth defects.