Which of the following most accurately describes the function of genes?

Correct Answer: A

Rationale: The correct answer is A: 'They regulate the development of traits.' Genes play a crucial role in regulating the development of traits by encoding proteins that control various bodily functions and characteristics. This process involves gene expression and the production of proteins that ultimately determine an individual's traits. Choice B is incorrect because genes do not have a direct role in preventing foreign particles from entering the body; this function is primarily carried out by the immune system. Choice C is incorrect as genes do not specifically work with lutein to influence development; genes operate independently to regulate trait expression. Choice D is incorrect as genes are not responsible for transferring oxygen in the bloodstream; this function is carried out by red blood cells and hemoglobin.

Correct Answer: D

Rationale: The correct answer is D because feeling quickening typically occurs around 18-20 weeks of gestation, indicating fetal movement. This is an appropriate time to auscultate the fetal heart rate. Choice A is incorrect because a molar pregnancy is not a viable pregnancy, and auscultating the fetal heart rate in this case is not applicable. Choice B is incorrect because a crown-rump length of 7 weeks gestation is too early for fetal heart rate auscultation. Choice C is incorrect because a positive urine pregnancy test alone does not indicate the appropriate timing for fetal heart rate auscultation.

Correct Answer: C

Rationale: The correct answer is C. Mutations can occur due to environmental influences such as radiation, chemicals, or other external factors, leading to changes in the DNA sequence. Choice A is incorrect because mutations can also occur due to errors in DNA replication, not solely by chance. Choice B is incorrect as mutations affect the DNA sequence itself, not the production of specific cells. Choice D is incorrect because mutations involve changes in the DNA sequence and do not specifically involve the formation of the DNA structure.

Correct Answer: A

Rationale: The typical sex chromosome pattern for females is XX. Females have two X chromosomes, which is represented as XX. Choice B (XYY) is incorrect as it represents the sex chromosome pattern for males with an extra Y chromosome. Choice C (XY) is the sex chromosome pattern for males. Choice D (XXY) represents a genetic disorder known as Klinefelter syndrome, where males have an extra X chromosome.

Correct Answer: C

Rationale: A person is homozygous for a trait when they have two identical alleles for that trait. In this case, both alleles are the same, indicating a homozygous genotype. Choice A, 'monozygous,' is incorrect as it refers to identical twins originating from a single fertilized egg. Choice B, 'dizygous,' is also incorrect as it refers to fraternal twins or individuals that develop from two separate fertilized eggs. Choice D, 'hemizygous,' is incorrect because it describes a genetic condition where only one allele is present in a diploid organism, typically related to genes on the sex chromosomes.