which is true of the term phenotype

HESI A2

HESI A2 Biology Practice Test

1. Which is true of the term Phenotype?

A. It is the genetic code
B. Phenotype determines genotype
C. Genotype determines phenotype
D. Genotype, epigenetic factors, and environmental factors determine phenotype

Correct answer: D

Rationale: The term "phenotype" refers to the observable characteristics or traits of an organism, which are determined by a combination of genotype (genetic makeup), epigenetic factors (modifications to gene expression), and environmental factors (external influences and experiences). Genotype, epigenetic factors, and environmental factors all play a role in determining an individual's phenotype, making option D the correct statement. Options A, B, and C are incorrect because the phenotype is not the genetic code, the phenotype does not determine the genotype, and it is the genotype that influences the phenotype, not the other way around.

2. What is the initial step in the metabolism of food to cellular energy?

A. Citric Acid Cycle
B. Glycolysis
C. Electron Transport Chain
D. Photosynthesis

Correct answer: B

Rationale: The correct answer is B: Glycolysis. Glycolysis is the initial step in the metabolism of food to cellular energy. During glycolysis, glucose is broken down into pyruvate, generating ATP and NADH. Choices A, C, and D are incorrect because the Citric Acid Cycle and Electron Transport Chain occur later in cellular respiration, while Photosynthesis is the process by which plants convert light energy into chemical energy.

3. Which of the following cell types has no nucleus?

A. platelet
B. red blood cell
C. white blood cell
D. phagocyte

Correct answer: B

Rationale: The correct answer is B, red blood cell. In humans, red blood cells do not have a nucleus. This unique feature allows them to have more space to carry oxygen efficiently. Platelets (choice A), white blood cells (choice C), and phagocytes (choice D) all have nuclei. Platelets are cell fragments, while white blood cells and phagocytes are types of immune cells that contain a nucleus for DNA and cellular functions.

4. In order, from lower to upper, the layers of the atmosphere are:

A. Exosphere, thermosphere, mesosphere, stratosphere, troposphere
B. Troposphere, stratosphere, mesosphere, thermosphere, exosphere
C. Mesosphere, troposphere, stratosphere, thermosphere, exosphere
D. Thermosphere, troposphere, stratosphere, mesosphere, exosphere

Correct answer: B

Rationale: The correct order of the layers of the atmosphere, from lower to upper, is troposphere, stratosphere, mesosphere, thermosphere, exosphere. The troposphere is the lowest layer where weather phenomena occur. The stratosphere contains the ozone layer, which absorbs and scatters the solar ultraviolet radiation. The mesosphere is where most meteorites burn up upon entering the Earth's atmosphere. The thermosphere is characterized by high temperatures due to the absorption of solar radiation. The exosphere is the outermost layer where the atmosphere transitions into space. Therefore, option B is the correct sequence, as it reflects the ascending order of the Earth's atmospheric layers.

5. Which organelle is responsible for making proteins?

A. Ribosome
B. Chloroplast
C. Lysosome
D. Mitochondrion

Correct answer: A

Rationale: Ribosomes are the organelles responsible for protein synthesis within the cell. They are the sites where amino acids are linked together to form proteins based on the instructions carried by mRNA (messenger RNA). Ribosomes can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum, and they play a crucial role in translating genetic information into proteins. Chloroplasts are responsible for photosynthesis, lysosomes are involved in digestion and waste removal, and mitochondria are known as the powerhouse of the cell responsible for energy production through cellular respiration. Therefore, the ribosome is the correct organelle responsible for making proteins.