how many different types of nucleotides are there in dna
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HESI A2

HESI A2 Practice Test Biology

1. How many different types of nucleotides are there in DNA?

Correct answer: C

Rationale: The correct answer is 'C: four.' DNA is composed of four different types of nucleotides: adenine, thymine, guanine, and cytosine. These nucleotides pair up in specific combinations to form the genetic code. Choices 'A: one,' 'B: two,' and 'D: eight' are incorrect because DNA consists of a set of four distinct nucleotides, not one, two, or eight.

2. What propels the cell forward?

Correct answer: B

Rationale: Propulsion, not microfilaments, cilia, or flagella, is what drives the cell forward. Propulsion is the force or process that propels the cell forward and allows it to move within its environment. Microfilaments are involved in cell structure, cilia are small hair-like structures for movement, and flagella are tail-like structures used for cell propulsion in some organisms.

3. The fur color in a population of dogs is controlled by two alleles: black (B) and tan (b). The black allele exhibits complete dominance. If the phenotype of the dog is tan fur, what is its genotype?

Correct answer: C

Rationale: The correct answer is C: "bb." Since tan fur is the recessive trait controlled by the allele 'b,' the only possible genotype for a dog with tan fur is 'bb.' If a dog had the genotype 'BB' or 'Bb,' the dominant trait (black fur) would be expressed, not tan fur. Choice D, 'Not enough information,' is incorrect because based on the information provided, we can deduce the genotype of a dog with tan fur.

4. Which of the following is a tertiary consumer?

Correct answer: A

Rationale: The correct answer is A, Owl. Tertiary consumers are organisms that feed on secondary consumers, which, in turn, feed on primary consumers. Owls are considered tertiary consumers because they primarily feed on animals such as rodents, which are secondary consumers. Shrew (choice B) is a secondary consumer, feeding on insects and worms, placing it at a lower trophic level than the owl. Grasshopper (choice C) is a primary consumer, feeding on plants. Wheat (choice D) is not a consumer in the food chain but a plant.

5. What type of transport moves substances across the cell membrane using energy?

Correct answer: B

Rationale: The correct answer is B: Active Transport. Active transport moves substances across the cell membrane by utilizing energy from the cell, typically in the form of ATP. This process allows the cell to move molecules against their concentration gradient, requiring energy expenditure. Choices A, C, and D are incorrect because passive transport does not require energy input, facilitated diffusion involves the assistance of proteins but does not directly use energy, and osmosis is the diffusion of water molecules specifically, not substances, across a selectively permeable membrane.

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