HESI A2 Practice Test Biology

Correct Answer: A

Rationale: The correct answer is A because tRNA carries amino acids to the ribosome during protein synthesis. Firstly, tRNA molecules bind to specific amino acids through their anticodon region. Secondly, tRNA recognizes the mRNA codon at the ribosome, ensuring the correct amino acid is added to the growing polypeptide chain. This process is crucial for translating the genetic code into proteins. Choices B, C, and D are incorrect because tRNA does not link nucleotides together, copy DNA sequences, or replicate genetic material during protein synthesis.

Correct Answer: C

Rationale: The correct answer is C: four. DNA is composed of four different types of nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). Each nucleotide consists of a nitrogenous base, a sugar (deoxyribose), and a phosphate group. These four nucleotides form complementary base pairs, which are essential for DNA replication and protein synthesis. The other choices are incorrect because DNA is made up of multiple nucleotides with specific base pairings, not just one or two types. Therefore, the correct answer is C: four.

Correct Answer: D

Rationale: The correct answer is D: Nucleus. The nucleus contains the genetic material of the cell, which is stored in the form of DNA. It controls the cell's activities and serves as the command center. The Golgi apparatus (A) is involved in processing and packaging proteins, the ribosome (B) is responsible for protein synthesis, and the endoplasmic reticulum (C) is involved in protein synthesis and lipid metabolism. The nucleus is unique in its role as the organelle that houses the cell's genetic information.

Correct Answer: B

Rationale: The correct answer is B: red blood cell. Red blood cells do not have a nucleus because during their maturation process, they eject their nucleus to make more space for hemoglobin which carries oxygen. Without a nucleus, red blood cells have more space to efficiently transport oxygen throughout the body. Platelets (A), white blood cells (C), and phagocytes (D) all have nuclei as they are involved in various cellular functions that require genetic material and the ability to replicate.

Correct Answer: D

Rationale: During meiosis I, the chromosome number is reduced from diploid to haploid. This occurs during the process of homologous chromosomes separating, resulting in two daughter cells with half the number of chromosomes. In contrast, in S phase, DNA replication occurs, while interphase is a period of cell growth and preparation for cell division. Mitosis is a process where a diploid cell divides into two identical diploid daughter cells, maintaining the same chromosome number. Thus, meiosis I is the only phase where the chromosome number is reduced from diploid to haploid, making it the correct answer.