HESI A2 BIOLOGY EXAM QUESTIONS AND ANSWERS
CORE DOMAINS
Cellular Structure and Function
Cell Cycle, Mitosis, and Meiosis
DNA, RNA, and Protein Synthesis
Genetics and Heredity
Metabolism, Enzymes, and Cellular Respiration
Photosynthesis and Plant Biology
Human Body Systems and Homeostasis
Ecology, Evolution, and Classification
INTRODUCTION
This comprehensive examination assesses the foundational biology
knowledge and critical thinking skills required for success on the HESI A2
Biology exam. It evaluates understanding of cellular processes, molecular
genetics, metabolism, human anatomy and physiology, and ecological
principles. The examination employs multiple-choice questions that
simulate realistic science reasoning tasks. Emphasis is placed on
application of biological concepts, interpretation of experimental data, and
integration of structure and function across biological levels of organization.
This assessment prepares candidates for the rigor of health science
programs and real-world clinical practice.
SECTION ONE: QUESTIONS 1–50
1. Which organelle is responsible for generating most of the ATP in a
eukaryotic cell?
A. Ribosome
B. Mitochondrion
C. Golgi apparatus
D. Lysosome
B. Mitochondrion
RATIONALE: Mitochondria carry out oxidative phosphorylation,
,producing the majority of cellular ATP. Ribosomes synthesize proteins, the
Golgi modifies and packages proteins, and lysosomes degrade waste.
2. During which phase of mitosis do sister chromatids separate and
move to opposite poles?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
C. Anaphase
RATIONALE: In anaphase, sister chromatids are pulled apart by spindle
fibers toward opposite poles. Prophase involves chromatin condensation,
metaphase aligns chromosomes at the metaphase plate, and telophase
reforms nuclei.
3. What is the complementary DNA strand for the sequence 5'-
ATGCGT-3'?
A. 5'-TACGCA-3'
B. 5'-ATGCGT-3'
C. 3'-TACGCA-5'
D. 5'-UACGCA-3'
A. 5'-TACGCA-3'
RATIONALE: DNA base pairing: A pairs with T, and C pairs with G. The
complementary strand runs antiparallel, so the sequence is 5'-TACGCA-3'.
Option D contains uracil, which is found in RNA, not DNA.
4. Which type of RNA carries amino acids to the ribosome during
translation?
A. mRNA
B. tRNA
C. rRNA
D. siRNA
, B. tRNA
RATIONALE: Transfer RNA (tRNA) transports specific amino acids to
the ribosome, where they are added to the growing polypeptide chain.
mRNA carries the genetic code, rRNA forms ribosomes, and siRNA is
involved in gene silencing.
5. A cross between two heterozygous tall pea plants (Tt × Tt)
produces what phenotypic ratio?
A. 1:1
B. 3:1
C. 9:3:3:1
D. 1:2:1
B. 3:1
RATIONALE: A monohybrid cross of two heterozygotes yields a 3:1
phenotypic ratio (3 tall : 1 short). The genotypic ratio is 1:2:1.
6. Which of the following is an example of a codominant trait in
humans?
A. Blood type AB
B. Red-green color blindness
C. Hemophilia
D. Sickle cell trait
A. Blood type AB
RATIONALE: In codominance, both alleles are expressed equally.
Blood type AB individuals express both A and B antigens. Red-green color
blindness and hemophilia are X-linked recessive traits. Sickle cell trait
shows incomplete dominance.
7. What is the primary function of the enzyme catalase?
A. Breaks down hydrogen peroxide into water and oxygen
B. Synthesizes ATP from ADP
C. Replicates DNA
D. Transports glucose into cells
CORE DOMAINS
Cellular Structure and Function
Cell Cycle, Mitosis, and Meiosis
DNA, RNA, and Protein Synthesis
Genetics and Heredity
Metabolism, Enzymes, and Cellular Respiration
Photosynthesis and Plant Biology
Human Body Systems and Homeostasis
Ecology, Evolution, and Classification
INTRODUCTION
This comprehensive examination assesses the foundational biology
knowledge and critical thinking skills required for success on the HESI A2
Biology exam. It evaluates understanding of cellular processes, molecular
genetics, metabolism, human anatomy and physiology, and ecological
principles. The examination employs multiple-choice questions that
simulate realistic science reasoning tasks. Emphasis is placed on
application of biological concepts, interpretation of experimental data, and
integration of structure and function across biological levels of organization.
This assessment prepares candidates for the rigor of health science
programs and real-world clinical practice.
SECTION ONE: QUESTIONS 1–50
1. Which organelle is responsible for generating most of the ATP in a
eukaryotic cell?
A. Ribosome
B. Mitochondrion
C. Golgi apparatus
D. Lysosome
B. Mitochondrion
RATIONALE: Mitochondria carry out oxidative phosphorylation,
,producing the majority of cellular ATP. Ribosomes synthesize proteins, the
Golgi modifies and packages proteins, and lysosomes degrade waste.
2. During which phase of mitosis do sister chromatids separate and
move to opposite poles?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
C. Anaphase
RATIONALE: In anaphase, sister chromatids are pulled apart by spindle
fibers toward opposite poles. Prophase involves chromatin condensation,
metaphase aligns chromosomes at the metaphase plate, and telophase
reforms nuclei.
3. What is the complementary DNA strand for the sequence 5'-
ATGCGT-3'?
A. 5'-TACGCA-3'
B. 5'-ATGCGT-3'
C. 3'-TACGCA-5'
D. 5'-UACGCA-3'
A. 5'-TACGCA-3'
RATIONALE: DNA base pairing: A pairs with T, and C pairs with G. The
complementary strand runs antiparallel, so the sequence is 5'-TACGCA-3'.
Option D contains uracil, which is found in RNA, not DNA.
4. Which type of RNA carries amino acids to the ribosome during
translation?
A. mRNA
B. tRNA
C. rRNA
D. siRNA
, B. tRNA
RATIONALE: Transfer RNA (tRNA) transports specific amino acids to
the ribosome, where they are added to the growing polypeptide chain.
mRNA carries the genetic code, rRNA forms ribosomes, and siRNA is
involved in gene silencing.
5. A cross between two heterozygous tall pea plants (Tt × Tt)
produces what phenotypic ratio?
A. 1:1
B. 3:1
C. 9:3:3:1
D. 1:2:1
B. 3:1
RATIONALE: A monohybrid cross of two heterozygotes yields a 3:1
phenotypic ratio (3 tall : 1 short). The genotypic ratio is 1:2:1.
6. Which of the following is an example of a codominant trait in
humans?
A. Blood type AB
B. Red-green color blindness
C. Hemophilia
D. Sickle cell trait
A. Blood type AB
RATIONALE: In codominance, both alleles are expressed equally.
Blood type AB individuals express both A and B antigens. Red-green color
blindness and hemophilia are X-linked recessive traits. Sickle cell trait
shows incomplete dominance.
7. What is the primary function of the enzyme catalase?
A. Breaks down hydrogen peroxide into water and oxygen
B. Synthesizes ATP from ADP
C. Replicates DNA
D. Transports glucose into cells
