Why is the genetic code redundant?

Correct Answer: A

Rationale: The genetic code is redundant because different codons can specify the same amino acid. This redundancy provides a buffer against mutations, ensuring that a change in a single nucleotide does not always result in a change in the amino acid being coded for. This redundancy allows for error correction during translation, increasing the robustness of the genetic code. Choices B, C, and D are incorrect because the redundancy in the genetic code is primarily for ensuring accuracy and reliability in protein synthesis, not for developing new amino acids or non-coding signals.

Correct Answer: B

Rationale: Correct Answer: B Rationale: 1. Mutations are random and constantly occurring in populations. 2. Deleterious alleles can arise from new mutations. 3. Selectively removing carriers won't prevent new mutations. 4. Thus, even if carriers are eliminated, new carriers will emerge, making it impossible to completely eradicate deleterious alleles. 5. This perpetual nature of mutations undermines any effort to eliminate deleterious alleles effectively.

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.