What mechanisms of genetic change are specific to sexual reproduction?

Correct Answer: D

Rationale: The correct answer is D (A and C). Independent assortment of chromosomes occurs during meiosis when homologous chromosomes separate randomly, leading to genetic variation in offspring. Recombination, or crossing over, also occurs during meiosis when genetic material is exchanged between homologous chromosomes, further increasing genetic diversity. Mutation (choice B) can occur in both sexual and asexual reproduction, so it is not specific to sexual reproduction. Choice D is correct because both independent assortment and recombination are unique mechanisms of genetic change in sexual reproduction, leading to genetic variation in offspring.

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: 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.