HESI RN
Biology Test
1. The term pleiotropy is best defined as which of the following?
- A. A situation in which one gene remains unexpressed
- B. One gene influencing multiple, seemingly unrelated phenotypic traits
- C. Two genes affected by a single allele
- D. A condition in which multiple genes are missing
Correct answer: B
Rationale: Pleiotropy is best defined as one gene influencing multiple, seemingly unrelated phenotypic traits. This phenomenon showcases the multifunctionality of genes, where a single gene can have effects on various aspects of an organism's phenotype. Choices A, C, and D do not accurately capture the concept of pleiotropy. Option A refers to gene expression, not pleiotropy. Option C describes genetic interactions but not in the context of pleiotropy. Option D talks about missing genes, which is unrelated to the definition of pleiotropy.
2. Which of the following is the term used to represent alternative versions of a gene?
- A. Alleles
- B. Binary fission
- C. Heterozygous
- D. Homozygous
Correct answer: A
Rationale: The correct answer is A: Alleles. Alleles are different versions of a gene that can exist at a specific locus on a chromosome. This term specifically refers to the different forms of a gene that can exist. Choices B, C, and D are incorrect because they do not represent alternative versions of a gene. Binary fission is a form of asexual reproduction in single-celled organisms, while heterozygous and homozygous refer to the genetic makeup of an individual rather than alternative versions of a gene.
3. In meiosis, the chromosome number is reduced from:
- A. 46 to 23
- B. 46 to 33
- C. 28 to 14
- D. 24 to 12
Correct answer: A
Rationale: The correct answer is A: "46 to 23." In meiosis, the chromosome number is reduced by half to form gametes for sexual reproduction. In humans, where the diploid chromosome number is 46, meiosis results in haploid cells with 23 chromosomes. Choices B, C, and D are incorrect because they do not represent the correct reduction in chromosome number during meiosis.
4. What is the liquid found inside the cell?
- A. Plasma membrane
- B. Cilia
- C. Cytoplasm
- D. Cytosol
Correct answer: D
Rationale: The correct answer is D, Cytosol. Cytosol is the liquid component of the cytoplasm where various cellular processes occur. Choices A, B, and C are incorrect because the plasma membrane is the outer boundary of the cell, cilia are hair-like structures on the cell surface, and cytoplasm is the jelly-like substance that contains organelles within the cell, not the liquid inside the cell.
5. In the hierarchical organizational system, which of these is the most restrictive category?
- A. Genus
- B. Class
- C. Kingdom
- D. Species
Correct answer: D
Rationale: In the biological classification hierarchy, species is the most specific level, defining individual organisms that can interbreed. While genus, class, and kingdom are also categories in the hierarchy, they are broader and encompass a wider range of organisms compared to species. Genus groups together similar species, class groups similar orders, and kingdom is the broadest category grouping together similar phyla.
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