Nokea
What scientific term encompasses a permanent alteration in the DNA sequence?
- A. Trait
- B. Mutation
- C. Allele
- D. Variation
Correct Answer: B
Rationale: A) Trait: A trait is a characteristic or feature of an organism that is determined by its genes.
B) Mutation: A mutation is a permanent alteration in the DNA sequence that can result from errors during DNA replication, exposure to mutagens, or other factors.
C) Allele: An allele is a variant form of a gene that can result in different traits or characteristics.
D) Variation: Variation refers to the differences in traits or characteristics among individuals of the same species, which can be influenced by genetic and environmental factors.
In this context, the term that specifically refers to a permanent alteration in the DNA sequence is "mutation."
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Why are isotopes of the same element chemically similar?
- A. They have the same number of protons.
- B. They have the same number of electrons.
- C. Their chemical properties are identical.
- D. They share the same electron configuration.
Correct Answer: A
Rationale: Isotopes of the same element are chemically similar because they have the same number of protons. The number of protons in an atom determines its atomic number, which is the defining characteristic of an element. Since chemical reactions primarily involve interactions between the electrons of atoms, having the same number of protons means the atoms have the same basic chemical properties. While isotopes may differ in the number of neutrons, it is the number of protons that dictates the element's identity and chemical behavior. Therefore, choice A is correct because the number of protons directly influences an element's chemical properties, making isotopes of the same element chemically similar despite potentially having different numbers of neutrons. Choices B, C, and D are incorrect because isotopes of the same element can have different numbers of electrons, their chemical properties are not identical due to potential differences in neutron numbers, and although they may have similarities in electron configurations, it is the number of protons that is the key factor determining chemical behavior.
What is the primary function of tight junctions, specialized regions between animal cells?
- A. Communication between cells
- B. Anchorage between cells
- C. Selective passage of materials
- D. All of the above
Correct Answer: C
Rationale: The correct answer is C: Selective passage of materials. Tight junctions act as specialized structures between animal cells that create a barrier to the passage of materials. Their primary function is to prevent the leakage of extracellular fluid and control the selective passage of molecules between cells. This selective control is crucial in regulating the movement of substances across cell layers. Tight junctions do not directly facilitate communication between cells or provide anchorage between cells, as their main role is to regulate the passage of materials. Choices A and B are incorrect as tight junctions do not primarily serve for communication or anchorage between cells.
What is the name for the change in enthalpy (heat) associated with a chemical reaction at constant pressure?
- A. Entropy
- B. Enthalpy
- C. Gibbs free energy
- D. Heat of reaction
Correct Answer: D
Rationale: The correct answer is D, Heat of reaction. The heat of reaction, also known as the enthalpy change, is the amount of heat absorbed or released during a chemical reaction at constant pressure. Entropy (A) is a measure of the disorder or randomness of a system and is not specifically related to heat changes in a chemical reaction. Enthalpy (B) is the total heat content of a system and not just the change associated with a reaction. Gibbs free energy (C) is a measure of the energy available to do work in a system at constant temperature and pressure, but it is not the specific term for the heat change in a chemical reaction.
What is the term for a group of organisms with the same genetic makeup?
- A. Population
- B. Clone
- C. Genotype
- D. Species
Correct Answer: B
Rationale: In this context, a clone (option B) is a group of organisms that are genetically identical because they are derived from a single ancestor. A population (option A) refers to a group of individuals of the same species living in the same area. Genotype (option C) refers to the genetic makeup of an individual organism. Species (option D) refers to a group of organisms that can interbreed and produce fertile offspring. Therefore, the most appropriate choice for the question is 'Clone,' as it specifically refers to organisms with the same genetic makeup.
When calcium chloride (CaCl2) dissolves in water, it separates into its ions (Ca2+ and Cl-). This is an example of:
- A. Chemical change
- B. Physical change
- C. Precipitation
- D. Neutralization
Correct Answer: B
Rationale: When calcium chloride dissolves in water, it separates into its ions without forming a new substance, which is characteristic of a physical change. A physical change involves alterations in the substance's physical properties without changing its chemical composition. In this scenario, the chemical formula of calcium chloride remains unchanged, and only its physical state changes by creating ions in the solution. Therefore, the dissolution of calcium chloride in water is an example of a physical change. Choice A, 'Chemical change,' is incorrect because no new substances are formed during the dissolution process. Choice C, 'Precipitation,' is incorrect as precipitation involves the formation of an insoluble solid when two solutions react. Choice D, 'Neutralization,' is incorrect as it refers to a reaction between an acid and a base to form salt and water, which is not the case in the given scenario.