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Example Question #9 : Hormone Origins And Targets
Scientists use a process called Flourescent In-Situ Hybridization, or FISH, to study genetic disorders in humans. FISH is a technique that uses spectrographic analysis to determine the presence or absence, as well as the relative abundance, of genetic material in human cells.
To use FISH, scientists apply fluorescently-labeled bits of DNA of a known color, called probes, to samples of test DNA. These probes anneal to the sample DNA, and scientists can read the colors that result using laboratory equipment. One common use of FISH is to determine the presence of extra DNA in conditions of aneuploidy, a state in which a human cell has an abnormal number of chromosomes. Chromosomes are collections of DNA, the totality of which makes up a cell’s genome. Another typical use is in the study of cancer cells, where scientists use FISH labels to ascertain if genes have moved inappropriately in a cell’s genome.
Using red fluorescent tags, scientists label probe DNA for a gene known to be expressed more heavily in cancer cells than normal cells. They then label a probe for an immediately adjacent DNA sequence with a green fluorescent tag. Both probes are then added to three dishes, shown below. In dish 1 human bladder cells are incubated with the probes, in dish 2 human epithelial cells are incubated, and in dish 3 known non-cancerous cells are used. The relative luminescence observed in regions of interest in all dishes is shown below.
Aneuploidy can also affect some fertilized zygotes after abnormalities in fertilization or gametogenesis. Aneuploid zygotes are typically spontaneously aborted before a pregnancy comes to term. A normal zygote binds to uterine endometrium while it is at its thickest, supported by progesterone secretion from which of the following?
Corpus luteum
Anterior pituitary
Graafian follicle
Hypothalamus
Posterior pituitary
Corpus luteum
The corpus luteum forms after ovulation, when a pregnancy would be most expected. The corpus luteum secretes progesterone, which maintains the endometrium for potential implantation.
Example Question #11 : Hormone Origins And Targets
Glucose levels in the blood are maintained through the competing actions of two main hormones: insulin and glucagon. Other hormones, such as somatostatin, and catecholamines, such as acetylcholine, also serve to modulate glucose levels in the blood. Which molecule is produced by the alpha cells of the islets of Langerhans in the pancreas?
Somatostatin
Glucagon
Acetylcholine
Insulin
Glucagon
Alpha cells in the islets of Langerhans are responsible for producing and secreting glucagon in response to high blood glucose levels. Insulin antagonizes the alpha cells to prevent glucagon release. In diabetes, when the beta cells of the pancreas are not functional, extremely high levels of glucagon exist in the blood due to loss of the negative feedback loop.
Beta and delta cells in the islets of Langerhans produce insulin and somatostatin, respectively. Neurons release acetylcholine to modulate glucose control through indirect processes.
Example Question #42 : Endocrine System
Which of the following hormones is least directly regulated by the anterior pituitary?
Cortisone
Thyroxine
Epinephrine
Progesterone
Epinephrine
Epinephrine is released from the adrenal medulla and regulated by the sympathetic system.
Cortisone, progesterone, and thyroxin are regulated by adrenocorticotropic hormone (ACTH), luteinizing hormone (LH), and thyroid-stimulating hormone (TSH), respectively. These regulatory hormones are all released from the anterior pituitary. ACTH acts on the adrenal cortex to stimulate glucocorticoid release, including cortisone. LH acts on the ovaries to mediate estrogen and progesterone release. TSH acts on the thyroid to mediate the release of T3 and T4. T4 is also known as thyroxine.
Example Question #43 : Endocrine System
Glucose levels in the blood are maintained through the competing actions of two main hormones: insulin and glucagon. Other hormones like somatostatin, and catecholamines, such as acetylcholine, also serve to modulate glucose levels in the blood. Which molecule is produced by the beta cells of the islets of Langerhans in the pancreas?
Insulin
Somatostatin
Glucagon
Acetylcholine
Insulin
Beta cells in the islets of Langerhans are responsible for producing and secreting insulin in response to high blood glucose levels. In type I diabetes these cells are destroyed by an autoimmune process, while in type II diabetes they are replaced with scar tissue.
Alpha and delta cells in the islets of Langerhans produce glucagon and somatostatin, respectively. Neurons release acetylcholine to modulate glucose control through indirect processes.
Example Question #44 : Endocrine System
Which of these is NOT true of steroid hormones?
They are derived from cholesterol.
They interfere at the level of transcription.
Their effects are long-lived.
They cannot cross the cell membrane.
Their receptors are usually located inside the cell.
They cannot cross the cell membrane.
Because of their nonpolar nature, steroid hormones can easily cross the cell membrane. This enables the hormone to work with its receptor, commonly located inside the cell. Their effects are long-lived since they involve genetic alteration at the transcription level. This, however, also means that steroid hormones take longer than peptide hormones to produce a response.
Example Question #44 : Endocrine System
Which of the following is NOT one of the tropic hormones released by the anterior pituitary?
Prolactin
LH
ACTH
TSH
FSH
Prolactin
Prolactin is an example of a non-tropic hormone released by the anterior pituitary.
Example Question #12 : Hormone Origins And Targets
A male gymnast is suspected for using anabolic steroids (i.e. testosterone) to enhance in his athletic performance. Which of the following would you expect to be decreased in his blood?
Luteinizing hormone only
Gonadotropin-releasing hormone only
Luteinizing hormone and follicle-stimulating hormone
Luteinizing hormone, follicle-stimulating hormone, and gonadotropin-releasing hormone
Gonadotropin-releasing hormone and luteinizing hormone
Luteinizing hormone, follicle-stimulating hormone, and gonadotropin-releasing hormone
All three hormones—luteinizing hormone, follicle-stimulating hormone, and gonadotropin-releasing hormone—are part of the hypothalamic-pituitary-gonadal axis. One should be familiar with this axis and with the fact that testosterone exerts negative control at both the level of the hypothalamus and the anterior pituitary.
Example Question #51 : Endocrine System
Which of the following hormones is not synthesized in the pituitary gland?
Growth hormone
Prolactin
Oxytocin
Adrenocorticotropic hormone
Oxytocin
Oxytocin is the only hormone mentioned that is synthesized in the hypothalamus, but secreted by the posterior pituitary.
Example Question #655 : Systems Biology And Tissue Types
There are a large variety of over-the-counter pregnancy tests, although all of them share a set of common principles.
These home pregnancy tests are immunoassays which detect the presence of the peptide hormone human chorionic gonadotropin (hCG). hCG is produced by the fertilized ovum and released into the mother's bloodstream, preventing the degradation of the corpus luteum and thereby preventing menstruation. By the time of the mother's first missed period, hCG levels in the urine are high enough to detect.
The home pregnancy test generally involves dipping a stick containing immobilized hCG monoclonal antibodies into a urine sample. If hCG is present in the urine, it will bind to the monoclonal antibodies on the dipstick. The dipstick is then placed in a solution containing a second monoclonal antibody which recognizes the bound hCG antibody complex on the surface of the dipstick. This second antibody is conjugated to colloidal gold particles which change color when they are immobilized, indicating a positive test result (i.e., pregnancy).
As described in the passage, the home pregnancy test __________.
is only effective after at least one month of pregnancy
is inaccurate because hCG is sometimes not produced by the fertilized zygote
accuracy improves when administered during early morning hours
lacks positive and negative controls
is inaccurate because hCG can be produced normally in the non-pregnant mother
lacks positive and negative controls
The test, as described in the passage, simply assays for the presence of hCG in the urine. The person using the test would either obtain a positive or negative result. Whether or not this result is valid remains in question because there are no experimental controls involved. In other words, there is nothing to test whether the test reagents are faulty or the procedure was done incorrectly. A positive control would involve using a sample liquid containing hCG and testing to see whether the pregnancy test could actually detect it. If it can't, then something is wrong. A negative control might involve using a urine sample with no hCG in it and seeing if the test gives a false positive result. Such controls are not included in the test as described in the passage. The other answer choices can be eliminated. The answer: 'is only effective after at least one month of pregnancy' is wrong because the passage states that hCG levels are high enough to be detected by the time of the first missed period (anywhere from 7-14 days from the time of fertilization.)
The answer: 'is inaccurate because hCG can be produced normally in the non-pregnant mother,' can be eliminated because the mother does not produce hCG. If she did, the test would be entirely useless. Only the embryo produces the hormone. The answer choice, 'is inaccurate because hCG is sometimes not produced by the fertilized zygote,' is also incorrect because the embryo must produce hCG in order to prevent menstruation and maintain the corpus luteum. If it doesn't, menstruation will occur and the embryo will be sloughed off with the uterine lining.
Example Question #11 : Hormone Origins And Targets
There are a large variety of over-the-counter pregnancy tests, although all of them share a set of common principles.
These home pregnancy tests are immunoassays which detect the presence of the peptide hormone human chorionic gonadotropin (hCG). hCG is produced by the fertilized ovum and released into the mother's bloodstream, preventing the degradation of the corpus luteum and thereby preventing menstruation. By the time of the mother's first missed period, hCG levels in the urine are high enough to detect.
The home pregnancy test generally involves dipping a stick containing immobilized hCG monoclonal antibodies into a urine sample. If hCG is present in the urine, it will bind to the monoclonal antibodies on the dipstick. The dipstick is then placed in a solution containing a second monoclonal antibody which recognizes the bound hCG antibody complex on the surface of the dipstick. This second antibody is conjugated to colloidal gold particles which change color when they are immobilized, indicating a positive test result (i.e., pregnancy).
The mechanism by which hCG acts on its target cells is most similar to that of __________.
testosterone
glucagon
aldosterone
estradiol
progesterone
glucagon
From the passage we learn that hCG is a peptide hormone. Peptide hormones act by binding to receptors on the plasma membranes of their target cells. This binding then triggers a signaling cascade which results in the transcription of specific genes. Peptide hormones can't cross the plasma membrane directly because they are not lipid soluble. Glucagon is a peptide hormone secreted by the alpha cells of the pancreas; it therefore uses a similar mechanism to that of hCG.The other answer choices can be eliminated because they are steroid hormones. These act by directly crossing the plasma membrane and binding to receptors either in the cytoplasm or in the nucleus.
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