Differential mRNA splicing

Correct Answer: B

Rationale: The correct answer is B because differential mRNA splicing involves removing introns and joining exons from a single primary RNA transcript to create various mRNA isoforms. This process allows for the production of multiple proteins from a single gene, increasing genetic diversity. Choice A is incorrect because mRNA splicing does not involve creating a backup copy of DNA. Choice C is incorrect as mRNA carries the genetic code to the ribosomes, not the cytoplasm. Choice D is incorrect because ribosomes are not held together by mRNA splicing; they are composed of proteins and rRNA.

Correct Answer: B

Rationale: The correct answer is B because triploidy involves the presence of one extra set of haploid chromosomes, resulting in a total of three sets (3n), while tetraploidy involves two extra sets, resulting in a total of four sets (4n). This leads to abnormal chromosome numbers in cells. Choice A is incorrect because triploidy and tetraploidy do not refer to specific chromosomes but to the number of whole sets of chromosomes. Choice C is incorrect as triploidy and tetraploidy do not directly relate to sexual characteristics. Choice D is incorrect as triploidy and tetraploidy are not caused by chromosome breakage due to radiation but rather by errors in cell division during fertilization.

Correct Answer: C

Rationale: The correct answer is C because small chromosome deletions involving a number of linked genes can lead to contiguous gene syndromes due to the deletion affecting multiple genes in close proximity. This can result in a cluster of related symptoms or phenotypes. Choices A and B are incorrect because the presence or absence of centromere or telomere in the deletion does not directly lead to contiguous gene syndromes. Choice D is incorrect as the deletion affecting genes at the breakpoints may not necessarily cause contiguous gene syndromes unless multiple genes in close proximity are involved.

Correct Answer: B

Rationale: The correct answer is B because maternal serum testing is complicated due to the fact that none of the available tests are individually definitive for fetal abnormalities. This means that a single test cannot conclusively determine the presence or absence of abnormalities, requiring a combination of tests for a more accurate assessment. Other choices are incorrect because A focuses on the quality of tests rather than their definitive nature, C mentions the involvement of health care professionals which is not the main reason for complexity, and D refers to the contents of maternal serum rather than the limitations of individual tests.

Correct Answer: B

Rationale: The correct answer is B because FISH (Fluorescence In Situ Hybridization) uses specific DNA probes that target a particular chromosome or chromosomal region. This allows for the visualization and analysis of specific genetic information without the need for spreads of mitotic chromosomes. Choice A is incorrect because FISH does not necessarily use DNA from whole chromosomes. Choice C is incorrect as chromosomes play a crucial role in genetic information. Choice D is incorrect because while chromosomes contain both DNA and protein, this is not the reason why FISH can provide genetic information without spreads of mitotic chromosomes.