Nokea
What is a rod-shaped structure that forms when a single DNA molecule and its associated proteins coil tightly before cell division?
- A. Centromere
- B. Chromatid
- C. Chromosome
- D. Gene
Correct Answer: C
Rationale: A chromosome is a rod-shaped structure that forms when a single DNA molecule and its associated proteins coil tightly before cell division. It contains the genetic material and is essential for cell division and replication. The centromere is a specific region of a chromosome that plays a role in cell division. A chromatid is one half of a duplicated chromosome, and a gene is a unit of heredity responsible for specific traits. Therefore, the correct answer is 'Chromosome' as it represents the entire condensed DNA molecule during cell division.
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Which of the following is a characteristic of an interneuron?
- A. Forms neural circuits
- B. Interacts with effectors
- C. Sends impulses to the CNS
- D. Functions as an efferent nerve cell
Correct Answer: A
Rationale: The correct characteristic of an interneuron is that it forms neural circuits, connecting sensory and motor neurons within the central nervous system. Interneurons facilitate communication between different neurons in the central nervous system, helping in the processing and integration of signals. Choice B is incorrect as interneurons primarily interact with other neurons, not effectors. Choice C is incorrect as interneurons typically do not send impulses to the CNS; they operate within the CNS. Choice D is incorrect as interneurons are not efferent nerve cells; they are mainly involved in processing signals within the CNS rather than transmitting signals to effectors.
How does the respiratory system facilitate gas exchange between air and blood?
- A. Diffusion
- B. Exhalation
- C. Inspiration
- D. Ventilation
Correct Answer: A
Rationale: The correct answer is 'Diffusion.' Diffusion is the process by which gases are exchanged between air in the alveoli and blood in the capillaries. Oxygen moves from the alveoli into the blood, while carbon dioxide moves from the blood into the alveoli through diffusion. Exhalation is the process of expelling air from the lungs, inspiration is the process of inhaling air into the lungs, and ventilation refers to the overall movement of air in and out of the lungs. While these processes are essential for the respiratory system to function, they are not directly responsible for the gas exchange between air and blood, which is primarily achieved through diffusion.
In a study evaluating which type of road salt deices a road most quickly, what is the independent variable?
- A. Deicing time period
- B. Road used for deicing
- C. Type of road salt used
- D. Amount of road salt used
Correct Answer: C
Rationale: The correct answer is C, 'Type of road salt used.' In an experiment, the independent variable is the one manipulated by the researcher to observe its impact on the dependent variable. In this study, the researchers are altering the type of road salt used to determine its influence on the deicing speed, thus making it the independent variable. The other choices are not the independent variable as they are not deliberately manipulated in the experiment: A - 'Deicing time period' is an outcome measure dependent on the type of salt used; B - 'Road used for deicing' is not controlled or manipulated; D - 'Amount of road salt used' would be a potential confounding variable rather than the independent variable as it could affect the outcome along with the type of salt.
At which of the following ages would ossification most likely take place to replace cartilage at the growth plate?
- A. 5
- B. 18
- C. 42
- D. 91
Correct Answer: B
Rationale: Ossification, the process where cartilage is replaced by bone, typically occurs during adolescence, around the age of 18. This is when the growth plates in the bones close, and the bones stop growing in length, leading to the replacement of cartilage with bone tissue. Choice A (5) is incorrect because ossification primarily occurs during adolescence, not early childhood. Choice C (42) is incorrect as ossification is completed well before this age, usually during the late teens or early twenties. Choice D (91) is incorrect as ossification is a process that occurs earlier in life, typically during adolescence, and is not a process that occurs in advanced age.
Not all cells in the pancreas secrete insulin because of the hormone somatostatin, which inhibits the release of insulin by all cells. What type of intercellular chemical signal does this illustrate?
- A. Autocrine
- B. Neuromodulator
- C. Paracrine
- D. Pheromone
Correct Answer: C
Rationale: The correct answer is C: Paracrine. Somatostatin acts in a paracrine manner by inhibiting the release of insulin from nearby cells within the pancreas. Paracrine signaling involves the secretion of signals that act on neighboring cells, as seen in this scenario where somatostatin affects nearby pancreatic cells without entering the bloodstream or affecting distant cells. Autocrine signaling involves cells responding to substances they themselves release, which is not the case here. Neuromodulators are chemicals that modulate the activity of neurons, not directly related to this scenario. Pheromones are chemicals released into the environment to communicate with individuals of the same species, not relevant to the signaling within the pancreas.