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What is the function of introns in eukaryotic genes?
- A. They code for protein sequences.
- B. They are involved in gene regulation.
- C. They are removed during mRNA processing.
- D. They are non-functional remnants of ancient DNA.
Correct Answer: C
Rationale: A) Introns do not code for protein sequences. Exons are the segments of DNA that code for proteins.
B) While introns can indirectly influence gene regulation, their primary function is not directly involved in gene regulation.
C) Introns are non-coding regions of DNA that are transcribed into pre-mRNA but are removed during mRNA processing through a process called splicing. This allows only the exons to be included in the mature mRNA that will be translated into proteins.
D) While introns were once thought to be non-functional remnants of ancient DNA, research has shown that they can have regulatory functions and play a role in gene expression.
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What is the basic unit of heredity?
- A. Chromosome
- B. Cell
- C. Gene
- D. Organ
Correct Answer: C
Rationale: A gene is the basic unit of heredity that carries the instructions for making proteins, which determine an organism's traits. Genes are segments of DNA located on chromosomes within the cell. While chromosomes contain many genes, a gene itself is the fundamental unit of heredity responsible for passing on genetic information from one generation to the next. Cells are the basic structural and functional units of living organisms, but genes specifically carry genetic information. Organs are composed of tissues and serve specific functions within an organism, but they are not the basic unit of heredity.
Differentiate between gene therapy and genetic engineering in the context of human intervention.
- A. Gene therapy aims to modify existing genes within body cells, while genetic engineering manipulates genes in embryos to be passed on to offspring.
- B. Gene therapy focuses on treating genetic diseases, while genetic engineering enhances desirable traits or eliminates undesirable ones.
- C. Both involve directly altering the DNA sequence, but gene therapy targets somatic cells and genetic engineering modifies germline cells.
- D. There is no fundamental difference; both terms are synonymous.
Correct Answer: B
Rationale: A) Incorrect. Gene therapy does aim to modify existing genes within body cells, but genetic engineering does not necessarily manipulate genes in embryos to be passed on to offspring. Genetic engineering can involve modifying genes in any type of cell, not just embryos.
B) Correct. Gene therapy is a medical intervention that aims to treat genetic diseases by correcting or replacing faulty genes within an individual's body cells. On the other hand, genetic engineering involves modifying genes to enhance specific traits or eliminate undesirable ones, often in the context of agriculture or biotechnology.
C) Incorrect. While both gene therapy and genetic engineering involve altering DNA sequences, the distinction lies in the target cells. Gene therapy targets somatic cells (non-reproductive cells), while genetic engineering typically involves modifying germline cells (reproductive cells that can pass on genetic changes to offspring).
D) Incorrect. There is
Which factor most significantly affects the kinetic energy of an object?
- A. The object's mass
- B. The object's velocity
- C. The object's displacement
- D. The object's potential energy
Correct Answer: B
Rationale: Kinetic energy is directly proportional to the square of an object's velocity. This means that changes in velocity have a greater impact on the kinetic energy of an object compared to changes in mass, displacement, or potential energy. The mass of an object affects its kinetic energy, but the effect is linear, not squared like velocity. Displacement does not directly affect kinetic energy, as it is a measure of the change in position, not related to motion. Potential energy is a different form of energy and is not directly related to the kinetic energy of an object. Therefore, the velocity of an object has the most significant effect on its kinetic energy.
Endotoxins are toxic substances released by:
- A. Viruses
- B. Bacteria (gram-positive)
- C. Bacteria (gram-negative)
- D. Parasites
Correct Answer: C
Rationale: Endotoxins are toxic substances that are part of the outer membrane of the cell wall of gram-negative bacteria. These toxins are released when the bacteria are destroyed or during bacterial growth. Endotoxins can cause a variety of harmful effects in the host, including fever, inflammation, and septic shock. Viruses do not produce endotoxins; they are typically associated with producing viral proteins that can be toxic to host cells. Gram-positive bacteria produce exotoxins, which are different from endotoxins found in gram-negative bacteria. Parasites, though capable of causing diseases, are not typically associated with the production of endotoxins.
Which of the following is NOT a mechanism of evolution?
- A. Natural selection
- B. Genetic drift
- C. Lamarckism
- D. Mutation
Correct Answer: C
Rationale: A) Natural selection is a mechanism of evolution where individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to the next generation.
B) Genetic drift is a mechanism of evolution that occurs due to random changes in allele frequencies in a population.
C) Lamarckism, also known as the inheritance of acquired characteristics, is a discredited theory that suggests organisms can pass on traits acquired during their lifetime to their offspring. This mechanism has been largely rejected by the scientific community.
D) Mutation is a mechanism of evolution that introduces new genetic variation into a population, which can lead to the emergence of new traits and adaptations over time.