Nokea
What is the definition of a gene?
- A. all the DNA in a cell that controls metabolic reactions
- B. a length of DNA that codes for a protein
- C. the nucleus and its chromosomes
- D. all the DNA in a cell that determines the inheritance of sex
Correct Answer: B
Rationale: The correct answer is B: a length of DNA that codes for a protein. Genes are specific sequences of DNA that encode instructions for building proteins. This is the fundamental role of genes in the process of protein synthesis. Choice A is incorrect because not all DNA in a cell controls metabolic reactions; some DNA is non-coding. Choice C is incorrect as it refers to the entire nucleus and its contents, not just the gene. Choice D is incorrect as genes do not solely determine the inheritance of sex; they also code for other traits. In summary, the definition of a gene as a segment of DNA that codes for a protein aligns with the known function and role of genes in genetics and molecular biology.
You may also like to solve these questions
Which sequence is part of the life cycle of a very large mass star?
- A. red giant → planetary nebula + neutron star
- B. red giant → planetary nebula + black hole
- C. red supergiant → supernova → neutron star
- D. red supergiant → supernova → black hole
Correct Answer: D
Rationale: The correct answer is D: red supergiant → supernova → black hole. This sequence is part of the life cycle of a very large mass star. Red supergiants are massive stars in the later stages of their evolution. When a red supergiant goes supernova, it explodes in a massive stellar explosion, leaving behind a remnant that can collapse into a black hole due to the immense gravitational forces. Choices A and B are incorrect because planetary nebulae form from the outer layers of lower mass stars, not very large mass stars. Choice C is incorrect as neutron stars are more likely to form from the remnants of less massive stars.
Steroid hormones _____________________.
- A. bind to a receptor inside the target cell
- B. are made from cholesterol
- C. cause the cell to make new proteins
- D. all of these
Correct Answer: D
Rationale: The correct answer is D because steroid hormones bind to a receptor inside the target cell, are made from cholesterol, and cause the cell to make new proteins. This is known as the mechanism of steroid hormone action. Choice A is correct as steroid hormones need to bind to intracellular receptors to exert their effects. Choice B is also correct as steroid hormones are derived from cholesterol. Choice C is correct as one of the main actions of steroid hormones is to regulate gene expression and induce the synthesis of new proteins within the cell. Therefore, all of these statements are true regarding steroid hormones, making choice D the correct answer.
Hyperglycemia, glucosuria, polyuria, and acidosis are:
- A. most apt to be caused by a deficiency of insulin.
- B. characteristic of diabetes insipidus.
- C. the consequences of a hormone-secreting tumor of the beta cells of the islets of Langerhans.
- D. indicative of a deficiency of ADH.
Correct Answer: A
Rationale: Step-by-step rationale for choice A being correct:
1. Hyperglycemia is high blood sugar due to insufficient insulin to regulate glucose levels.
2. Glucosuria is the presence of glucose in urine, indicating excess blood sugar not being reabsorbed.
3. Polyuria is increased urine production due to osmotic diuresis from excess glucose in the urine.
4. Acidosis results from the breakdown of fats in the absence of sufficient glucose utilization.
5. All these symptoms align with uncontrolled diabetes mellitus, where insulin deficiency leads to these metabolic disturbances.
Summary of why other choices are incorrect:
B: Diabetes insipidus is characterized by excessive thirst and urination due to inadequate ADH, not hyperglycemia.
C: Hormone-secreting tumor of beta cells would lead to hyperinsulinemia and hypoglycemia, not hyperglycemia.
D: ADH deficiency would result in dilute urine and electrolyte imbalances
Calcitonin is a hormone of which of following:
- A. Adrenal cortex.
- B. Thyroid gland.
- C. Pituitary gland.
- D. Thymus gland.
Correct Answer: B
Rationale: Calcitonin is a hormone produced by the thyroid gland. It helps regulate calcium levels in the body by inhibiting bone breakdown and lowering blood calcium levels. The thyroid gland is responsible for producing various hormones, including calcitonin. Adrenal cortex (A) produces hormones like cortisol, Pituitary gland (C) produces hormones like growth hormone, and Thymus gland (D) is involved in immune function, not hormone regulation. Therefore, the correct answer is B (Thyroid gland).
A patient presents with increased growth of skeletal and soft tissue, hypertension, arthritis, menstrual disturbances, and diabetes mellitus. Upon administration of oral glucose, which of the following levels would increase?
- A. GH
- B. IGF
- C. GH and IGF
- D. ADH
Correct Answer: B
Rationale: The correct answer is B: IGF. Increased growth of skeletal and soft tissue, along with other symptoms, suggest acromegaly due to excess growth hormone (GH) secretion. GH stimulates the liver to produce insulin-like growth factor (IGF), which mediates many of GH's effects. In acromegaly, elevated IGF levels contribute to the clinical manifestations. Option A (GH) is incorrect because GH levels may be high but not necessarily in response to oral glucose. Option C (GH and IGF) is incorrect as GH alone does not directly increase in response to oral glucose. Option D (ADH) is unrelated to the scenario described.