Nokea
Which of the following enzymes unwinds the double-stranded DNA during replication?
- A. Helicase
- B. Ligase
- C. Nuclease
- D. Polymerase
Correct Answer: A
Rationale: Helicase is the enzyme responsible for unwinding the double-stranded DNA during replication by breaking the hydrogen bonds between the base pairs. This process creates the replication fork where DNA polymerase can then synthesize new DNA strands. Ligase functions to join Okazaki fragments on the lagging strand, not unwind DNA. Nuclease is involved in DNA repair by removing damaged DNA segments. Polymerase is responsible for synthesizing new DNA strands based on the existing template strands, not for unwinding the DNA.
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What is the primary function of the respiratory system?
- A. To digest food
- B. To transport nutrients
- C. To exchange gases
- D. To regulate body temperature
Correct Answer: C
Rationale: The correct answer is C: To exchange gases. The primary function of the respiratory system is to facilitate the exchange of gases, specifically oxygen and carbon dioxide, between the body and the environment. This process is essential for cellular respiration, where oxygen is taken in and carbon dioxide is removed. Choices A, B, and D are incorrect. Digesting food is primarily the function of the digestive system, transporting nutrients is the role of the circulatory system, and regulating body temperature is primarily managed by the integumentary system and the nervous system, not the respiratory system.
Which type of joint connects the bones of the skull?
- A. Synovial
- B. Fibrous
- C. Cartilaginous
- D. Ball-and-socket
Correct Answer: B
Rationale: Fibrous joints connect the bones of the skull. These joints are immovable or provide very limited movement, providing stability and protection to the brain. Synovial joints (Choice A) are found in the limbs and allow for a wide range of movements. Cartilaginous joints (Choice C) are connected by cartilage and allow limited movement. Ball-and-socket joints (Choice D) allow for a wide range of motion, such as the hip and shoulder joints, but they do not connect the bones of the skull.
Which of the following is responsible for carrying oxygenated blood from the heart to the body?
- A. Vein
- B. Artery
- C. Capillary
- D. Lymphatic vessel
Correct Answer: B
Rationale: The correct answer is B: Artery. Arteries carry oxygenated blood away from the heart to the body. Veins carry deoxygenated blood back to the heart, capillaries are tiny blood vessels where gas exchange occurs, and lymphatic vessels are part of the lymphatic system, which is responsible for draining excess fluid from tissues and transporting white blood cells.
A botanist wants to determine if environmental temperature affects root growth. What is the independent variable in this study?
- A. Temperature
- B. Seedlings
- C. Light
- D. Root length
Correct Answer: A
Rationale: The correct answer is 'Temperature.' In an experiment, the independent variable is the factor that is deliberately manipulated or changed by the researcher. In this study, the botanist is specifically investigating how environmental temperature affects root growth, making temperature the independent variable. Choice B, 'Seedlings,' and Choice C, 'Light,' are not the independent variables in this context as they are not the factors being intentionally changed or manipulated. Choice D, 'Root length,' is the dependent variable, as it is the outcome that is being measured or observed in response to the changes in the independent variable, temperature.
Which part of the neuron receives signals from other neurons?
- A. Axon
- B. Dendrite
- C. Synapse
- D. Myelin sheath
Correct Answer: B
Rationale: The correct answer is B, Dendrite. Dendrites are the part of the neuron that receive signals from other neurons and transmit them to the cell body. Axons transmit signals away from the cell body, synapse is the junction between neurons where neurotransmitters are released, and myelin sheath is a fatty layer that insulates and speeds up signal conduction along the axon. Therefore, choices A, C, and D are incorrect in the context of receiving signals from other neurons.