HESI RN
Biology Practice Test
1. The Punnett square shows that one parent carries the recessive gene for a cleft chin (c) while the other parent does not. What percentage of the parents' offspring is predicted to have a cleft chin?
- A. 25%
- B. 50%
- C. 0%
- D. 75%
Correct answer: C
Rationale: The correct answer is 0%. If one parent carries the recessive gene for a cleft chin while the other parent does not, none of the offspring will express the recessive phenotype. This is because in order for a child to have a cleft chin, they would need to inherit the recessive gene from both parents. Therefore, although the offspring could be carriers of the gene, none are predicted to have a cleft chin. Choices A, B, and D are incorrect because the presence of the recessive gene in one parent and its absence in the other would not result in any offspring showing the cleft chin trait.
2. What must first occur before a cell can be divided to grow, develop, and reproduce organisms?
- A. RNA replication
- B. DNA replication
- C. Gene replication
- D. Chromosome replication
Correct answer: B
Rationale: The correct answer is B: DNA replication. Before a cell can divide to grow, develop, and reproduce organisms, DNA replication must occur. This process ensures that each daughter cell receives an identical set of genetic information. Choices A, C, and D are incorrect because while RNA, genes, and chromosomes are essential components of cell division, DNA replication is the specific process that must first occur to ensure accurate transmission of genetic material.
3. Water is a polar molecule that can be:
- A. cohesive and corrosive
- B. cohesive and adhesive
- C. electrostatic and ionic
- D. repellent and attractive
Correct answer: B
Rationale: Water is a polar molecule due to an uneven distribution of electrons, allowing it to form hydrogen bonds. This property makes water both cohesive (attracted to itself) and adhesive (attracted to other substances). Choice A is incorrect because water is not corrosive; rather, it is a solvent. Choices C and D are incorrect as they do not describe the cohesive and adhesive properties of water.
4. What is the composition of the cellular membrane?
- A. A bilayer of phospholipid molecules
- B. A single layer of phospholipid molecules
- C. Proteins that act as transport highways
- D. Carbohydrates
Correct answer: A
Rationale: The cellular membrane is primarily composed of a phospholipid bilayer, which consists of two layers of phospholipid molecules. These molecules have a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tail, creating a barrier that separates the internal cellular environment from the external surroundings. While proteins are embedded within this bilayer and act as transport channels, receptors, and structural support, carbohydrates are found on the outer surface of the membrane for cell recognition and signaling purposes. Therefore, the correct answer is a bilayer of phospholipid molecules.
5. Proteins are polymers of 20 molecules called:
- A. Amino acids
- B. Phospholipids
- C. Carbohydrates
- D. Fatty acids
Correct answer: A
Rationale: Proteins are indeed polymers made up of amino acids. Amino acids are the building blocks of proteins, where each protein has a unique sequence of amino acids that determines its structure and function. Phospholipids, carbohydrates, and fatty acids are not molecules that make up proteins. Phospholipids are the main components of cell membranes, carbohydrates are sugars used for energy and structural purposes, and fatty acids are building blocks of lipids.
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