the correct answer is d heterozygous traits contain one dominant and one recessive form of the gene which of the following is true of homozygous trait

HESI A2

Biology HESI A2 Practice Test

1. Which of the following is true of homozygous traits?

A. They are haploid
B. They are denoted AA
C. They are denoted aa
D. They are denoted Aa

Correct answer: B

Rationale: Homozygous traits have two identical forms of the gene, either both dominant (AA) or both recessive (aa). Therefore, choices B and C are true for homozygous traits. Choice A is incorrect because being haploid refers to having a single set of chromosomes, not necessarily homozygous traits. Choice D is incorrect as homozygous traits have identical alleles, so they are not denoted as Aa.

2. Which cells in the human body lack nuclei?

A. Nerve cells
B. Red blood cells
C. Liver cells
D. Connective tissue cells

Correct answer: B

Rationale: Red blood cells, also known as erythrocytes, lack nuclei in humans. This absence of a nucleus allows more space for hemoglobin, the protein responsible for carrying oxygen, making red blood cells efficient at their function of oxygen transport in the body. Nerve cells (Choice A), liver cells (Choice C), and connective tissue cells (Choice D) all possess nuclei as they require genetic material for their functions, such as cell signaling, protein synthesis, and structural support.

3. Beeswax is an example of what kind of molecule?

A. Lipid
B. Carbohydrate
C. Protein
D. Nucleic acid

Correct answer: A

Rationale: Beeswax is primarily composed of esters of long-chain aliphatic alcohols and fatty acids, making it a type of lipid. Lipids are a diverse group of molecules that are hydrophobic in nature and have important functions in energy storage, signaling, and forming cellular membranes. Beeswax's chemical composition and properties categorize it as a lipid rather than a carbohydrate, protein, or nucleic acid. Carbohydrates are composed of sugars, proteins are made up of amino acids, and nucleic acids consist of nucleotides; none of which match the chemical composition of beeswax.

4. Which of the following bases is not present in RNA?

A. Adenine
B. Thymine
C. Uracil
D. Cytosine

Correct answer: B

Rationale: Thymine is not present in RNA. RNA uses uracil as one of its bases, which pairs with adenine. In RNA, adenine does not pair with thymine as in DNA. Cytosine and guanine are the other two bases found in both RNA and DNA.

5. Which of the following is not true about enzymes?

A. They catalyze reactions
B. They lower the activation energy needed
C. They have an active site
D. They are typically proteins

Correct answer: B

Rationale: Enzymes lower the activation energy needed for a reaction to occur, not raise it. By lowering the activation energy, enzymes facilitate reactions, making them occur more easily and rapidly. Choice A is correct as enzymes indeed catalyze reactions. Choice C is correct as enzymes have specific active sites where substrates bind. Choice D is correct as enzymes are commonly proteins, although some RNA molecules also exhibit catalytic properties.