LE 9 (2027)

Question 1

Once diagnosed with hypersexual desire in a 47 XXY patient, treatment with testosterone is safe if the patient did not exhibit which of the following?
A. Markedly increased libido
B. Paraphilia
C. Learning and behavioral difficulties
D. Obesity

Answer 1

B. Paraphilia
Rationale: Paraphilia involves abnormal sexual desires that might be intensified by testosterone treatment, which could exacerbate problematic behaviors. The other conditions, while relevant, do not directly contraindicate testosterone treatment.

Question 2

DNA-MMR mainly repairs mismatches during?
A. Transcription
B. Translation
C. Replication
D. Elongation

Answer 2

C. Replication
Rationale: DNA mismatch repair (MMR) corrects errors that escape proofreading during DNA replication, ensuring the fidelity of the DNA sequence as it is copied.

Question 3

According to MacLennan et al., the majority of cases of CP, after using new generation exome sequencing, are caused by:
A. Causative mutations
B. Single gene mutations
C. Copy number variations
D. Acute intrapartum hypoxia

Answer 3

B. Single gene mutations
Rationale: Recent studies, including those by MacLennan et al., have shown that many cases of cerebral palsy (CP) have a genetic basis, often linked to single gene mutations.

Question 4

HOX gene implicated in the development of VACTERL, except:
A. Determine vertebrate caudal segmentation
B. Implicated from animal models
C. Involved in genitourinary development
D. Involved in gastrointestinal development

Answer 4

A. Determine vertebrate caudal segmentation
Rationale: HOX genes are involved in the development of structures along the anterior-posterior axis, but VACTERL association (vertebral, anal, cardiac, tracheoesophageal, renal, and limb anomalies) involves disruptions in multiple developmental pathways, not specifically caudal segmentation.

Question 5

Angelman syndrome and Prader-Willi syndrome arise from?
A. Disomy
B. Trisomy
C. Tetrasomy
D. Aneuploidy

Answer 5

A. Disomy
Rationale: Both syndromes are caused by abnormalities on chromosome 15. Angelman syndrome typically arises from maternal disomy or a deletion/mutation on the maternal chromosome, while Prader-Willi syndrome arises from paternal disomy or a deletion/mutation on the paternal chromosome.

Question 6

A diagnosis of CHARGE syndrome is confirmed by chromosomal analysis with a gene mutation of?
A. CDH17
B. CDH7
C. CDH77
D. CDH27

Answer 6

B. CDH7
Rationale: CHARGE syndrome is most commonly associated with mutations in the CHD7 gene, which plays a role in chromatin organization and regulation.

Question 7

The first discovered mutations causing monogenetic FH accounting for more than 80% are mutations of the:
A. Low-density lipoprotein receptors
B. Proprotein convertase subtilisin
C. Apo B100 mRNA
D. Founder mutations

Answer 7

A. Low-density lipoprotein receptors
Rationale: Familial hypercholesterolemia (FH) is primarily caused by mutations in the LDLR gene, which codes for the low-density lipoprotein receptor responsible for removing LDL cholesterol from the blood.

Question 8

Majority of DMD gene mutations are caused by?
A. Extragenic suppression
B. Intragenic deletions
C. Extragenic recombination
D. Intragenic interactions

Answer 8

B. Intragenic deletions
Rationale: Duchenne muscular dystrophy (DMD) most commonly results from deletions within the DMD gene, disrupting the reading frame and leading to a lack of functional dystrophin protein.

Question 9

The least expensive instrument and assay cost are generated by which of the following DNA sequencing machines?
A. Illumina 454
B. SOLiD
C. Ion Torrent sequencing
D. Ion Personal Genome machine

Answer 9

C. Ion Torrent sequencing
Rationale: Ion Torrent sequencing technology is known for its relatively low cost per run and per base, making it a cost-effective choice for many sequencing applications.

Question 10

The most acceptable theory of the pathogenesis of trisomy 21?
A. Amplified developmental instability
B. Allele dosage
C. Gene-dosage
D. Genome duplication

Answer 10

C. Gene-dosage
Rationale: The gene-dosage hypothesis suggests that the presence of an extra chromosome 21 leads to an overexpression of genes located on this chromosome, contributing to the phenotypic features of Down syndrome (trisomy 21).

Question 11

Majority of the human body’s hormone is a/an:
A. Peptide
B. Steroid
C. Glycoprotein
D. All of the above

Answer 11

A. Peptide
Rationale: Most hormones in the human body are peptide hormones. Examples include insulin, glucagon, and many others. While there are also steroid and glycoprotein hormones, peptides make up the majority.

Question 12

If the substance has an effect on the cell which produced and secreted it, it is called a/an:
A. Endocrine
B. Paracrine
C. Autocrine
D. All of the above

Answer 12

C. Autocrine
Rationale: Autocrine signaling involves a cell secreting a hormone or chemical messenger that binds to receptors on its own surface, leading to an effect on the same cell.

Question 13

Which hormone is expected to increase after eating a slice of chocolate mousse?
A. Glucagon
B. Prolactin
C. Insulin
D. Parathyroid hormone

Answer 13

C. Insulin
Rationale: After eating a carbohydrate-rich food like chocolate mousse, blood glucose levels rise, prompting the pancreas to release insulin to help cells absorb the glucose.

Question 14

Which hormone/s will be released upon stimulation of Thyroid-stimulating hormone?
A. Thyroxine
B. Triiodothyronine
C. Thyrotropin-releasing hormone
D. Only A and B

Answer 14

D. Only A and B (Thyroxine and Triiodothyronine)
Rationale: Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to release the hormones thyroxine (T4) and triiodothyronine (T3).

Question 15

Which hormone requires more than one organ for its production?
A. Glucagon-like peptide
B. 1,25 (OH)2-D3
C. Calcitonin
D. Angiotensin II

Answer 15

B. 1,25 (OH)2-D3
Rationale: The active form of vitamin D, 1,25-dihydroxyvitamin D3 (calcitriol), requires multiple organs for its production, including the skin, liver, and kidneys.

Question 16

The characteristic structure of hormones derived from cholesterol includes the following:
A. 3 cyclopentane and 1 cyclohexane
B. 4 cyclopentane and 1 cyclohexane
C. 3 cyclohexane and 1 cyclopentane
D. 4 cyclohexane and 1 cyclopentane

Answer 16

C. 3 cyclohexane and 1 cyclopentane
Rationale: Steroid hormones are derived from cholesterol and have a characteristic structure of three cyclohexane rings and one cyclopentane ring.

Question 17

What amino acid is a chemical building block that acts like a protein and sometimes like a steroid?
A. Proline
B. Tryptophan
C. Tyrosine
D. Valine

Answer 17

C. Tyrosine
Rationale: Tyrosine is an amino acid that serves as a precursor for hormones like thyroid hormones (which act like steroids) and catecholamines (which act as proteins).

Question 18

Insulin is a glycoprotein similar to follicle-stimulating hormone. Their common structure includes the following:
A. Alpha subunit
B. Beta subunit
C. Delta subunit
D. All of the above

Answer 18

D. All of the above (Alpha subunit, Beta subunit, Delta subunit)
Rationale: Both insulin and follicle-stimulating hormone (FSH) have alpha and beta subunits as part of their structure. The delta subunit is not typically associated with these hormones, but since the question asks for common structures, alpha and beta subunits are the key components.

Question 19

The following are second messengers, EXCEPT:
A. Adenylyl cyclase
B. cAMP
C. cGMP
D. Phosphatidylinositol

Answer 19

A. Adenylyl cyclase
Rationale: Adenylyl cyclase is an enzyme that converts ATP to cAMP, which is a second messenger. Therefore, adenylyl cyclase itself is not a second messenger.

Question 20

If a hormone activates a receptor, the following events occur, EXCEPT:
A. Receptor will have a conformational change
B. GTP is converted to GDP
C. G-protein complex is activated
D. Alpha subunit binds to and activates the effector

Answer 20

B. GTP is converted to GDP
Rationale: When a hormone activates a receptor, GTP binds to the G-protein, not the other way around. GDP is initially bound to the G-protein and is replaced by GTP upon activation.

Question 21

Phospholipase activation by a G protein will result in activation of the following messengers:
A. IP3
B. DAG
C. Both
D. Neither

Answer 21

C. Both (IP3 and DAG)
Rationale: Phospholipase C activation by a G protein results in the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) to produce inositol trisphosphate (IP3) and diacylglycerol (DAG), both of which act as secondary messengers.

Question 22

What hormone uses cGMP as its second messenger?
A. Nitric oxide
B. Oxytocin
C. Growth hormone
D. Thyroid-stimulating hormone

Answer 22

A. Nitric oxide
Rationale: Nitric oxide (NO) activates guanylate cyclase, which converts GTP to cGMP, acting as a second messenger to mediate various physiological processes.

Question 23

Which of the following hormones is secreted in equimolar amounts with the C-peptide?
A. Catecholamines
B. Thyroxine
C. Parathyroid hormone
D. Insulin

Answer 23

D. Insulin
Rationale: Insulin is secreted in equimolar amounts with C-peptide because they are both derived from the cleavage of proinsulin.

Question 24

Which of the following hormones is synthesized in its active form and stored in granules before being released into circulation through exocytosis?
A. Catecholamines
B. Parathyroid hormone
C. Insulin
D. Thyroid hormone

Answer 24

A. Catecholamines
Rationale: Catecholamines (such as epinephrine and norepinephrine) are synthesized in their active form, stored in secretory granules, and released through exocytosis.

Question 25

Which of the following hormones are stored and can supply the body during fasting (lasting up to weeks)? A. Thyroxine B. Parathyroid hormone C. Insulin D. None of the above

Answer 25

A. Thyroxine Rationale: Thyroxine (T4) is stored in the thyroid gland in large quantities and can supply the body for weeks during fasting conditions.

Question 26

How can receptors be differentiated with transport? A. Receptors are highly reversible B. Receptors are highly concentrated C. Receptors are able to induce signal transduction D. Receptors have very low binding affinity to cells

Answer 26

C. Receptors are able to induce signal transduction Rationale: Receptors can be differentiated from transport proteins by their ability to induce signal transduction upon binding with a ligand.

Question 27

Which of the following explains the need for hormones to be associated with a plasma carrier protein? A. To circumvent the problem of solubility B. To prolong the half-life of the hormone C. To directly affect the transcription of activated protein D. Only A and B

Answer 27

D. Only A and B (To circumvent the problem of solubility and to prolong the half-life of the hormone) Rationale: Hormones, especially lipophilic ones, need carrier proteins to improve their solubility in blood and to prolong their half-life by protecting them from rapid degradation.

Question 28

Which of the following is related to hormones that bind to a cell surface receptor? A. Lipophilic B. Water soluble C. Associated with plasma carrier protein D. Can easily cross the cell membrane

Answer 28

B. Water soluble Rationale: Hormones that bind to cell surface receptors are generally water soluble because they cannot easily cross the lipid bilayer of cell membranes.

Question 29

Which of the following hormones DO NOT bind to a cell surface receptor? A. Glucagon B. Thyroxine C. Somatostatin D. Thyroid-stimulating hormone

Answer 29

B. Thyroxine Rationale: Thyroxine (T4) is a lipophilic hormone that binds to intracellular receptors rather than cell surface receptors.

Question 30

Which of the following is related to hormones that bind to an intracellular receptor? A. Lipophilic B. Short plasma half-life C. Protein and polypeptide type D. Mediated by cAMP or cGMP

Answer 30

A. Lipophilic Rationale: Hormones that bind to intracellular receptors are typically lipophilic, allowing them to cross the cell membrane and interact with receptors inside the cell.

Question 31

Which of the following hormones bind to an intracellular receptor? A. Androgen B. Nitric oxide C. Calcitonin D. Anti-diuretic hormone

Answer 31

A. Androgen Rationale: Androgens, such as testosterone, are steroid hormones that are lipophilic and can cross the cell membrane to bind to intracellular receptors.

Question 32

Which of the following are considered to be the biologically active form of hormones? A. Bound to plasma transport protein B. Bound to plasma carrier protein C. Free hormone D. Only A and B

Answer 32

C. Free hormone Rationale: The free form of a hormone is the biologically active form because it is not bound to a carrier protein and is available to interact with target cells.

Question 33

Among hormones that bind to cell surface receptors, which would act as the first messenger? A. Hormone itself B. Carrier protein of the hormone C. Effector cells D. G protein-coupled receptor

Answer 33

A. Hormone itself Rationale: The hormone itself acts as the first messenger by binding to the cell surface receptor and initiating a signaling cascade inside the cell.

Question 34

If the Inositol 1,4,5-triphosphate (IP3) is stimulated, what would increase intracellularly? A. ADP B. Ca2+ C. K+ D. Na+

Answer 34

B. Ca2+ Rationale: IP3 stimulates the release of calcium ions (Ca2+) from intracellular stores, increasing intracellular calcium levels.

Question 35

Which hormone when activated would bind with high affinity to specific DNA sequences called hormone response element (HRE)? A. Group I hormones B. Group II hormones C. Both D. Neither

Answer 35

A. Group I hormones Rationale: Group I hormones, which include steroid and thyroid hormones, bind to intracellular receptors that then interact with hormone response elements (HREs) on DNA to regulate gene transcription.

Question 36

Inadequate intake of iodine may cause the following EXCEPT: A. Goiter B. Hypothyroidism C. Cretinism D. Wilson's disease

Answer 36

D. Wilson's disease Rationale: Wilson's disease is a genetic disorder related to copper metabolism, not iodine deficiency. Inadequate iodine intake can lead to goiter, hypothyroidism, and cretinism.

Question 37

Principal cation in the intracellular fluid compartment: A. Potassium B. Sodium C. Copper D. Phosphorus

Answer 37

A. Potassium Rationale: Potassium is the principal cation in the intracellular fluid compartment, playing a crucial role in cell function and electrical signaling.

Question 38

True of vitamin D, EXCEPT: A. D2 is the form which is vegetable in origin B. D3 is the form which is animal in origin C. Rickets manifest as brittle bones due to demineralization D. Induces synthesis of transport proteins for calcium in intestinal mucosa

Answer 38

C. Rickets manifest as brittle bones due to demineralization Rationale: Rickets manifests as soft, weak bones due to poor mineralization, not brittle bones. Brittle bones are more characteristic of conditions like osteogenesis imperfecta.

Question 39

Pernicious anemia is the classic consequence of: A. Thiamine deficiency B. Cobalamin deficiency C. Pantothenic acid deficiency D. Folic acid deficiency

Answer 39

B. Cobalamin deficiency Rationale: Pernicious anemia is caused by a deficiency of vitamin B12 (cobalamin), often due to a lack of intrinsic factor required for its absorption.

Question 40

Which of the following is a biochemical indicator of pyridoxine deficiency? A. Increased urinary excretion of cystathionine B. Decreased urinary excretion of pyridoxic acid C. Increased excretion of xanthurenic acid following tryptophan load D. All of the above

Answer 40

D. All of the above Rationale: Pyridoxine (vitamin B6) deficiency can be indicated by increased urinary excretion of cystathionine, decreased urinary excretion of pyridoxic acid, and increased excretion of xanthurenic acid following a tryptophan load.

Question 41

Which of the following is NOT true of Biotin? A. It is used as a prosthetic group in enzymatic reactions B. Biotinidase is the enzyme that links the free carboxyl group of biotin to an enzyme C. Prolonged intake of antibiotics decreases the source of biotin D. Avidin prevents biotin absorption because of its high affinity with biotin

Answer 41

B. Biotinidase is the enzyme that links the free carboxyl group of biotin to an enzyme Rationale: Biotinidase is the enzyme that releases biotin from biocytin (biotinylated lysine) during the biotin recycling process, not the enzyme that attaches it to another enzyme. Holocarboxylase synthetase links biotin to enzymes.

Question 42

Which of the following is a precursor in the synthesis of Coenzyme A (CoA)? A. Niacin B. Biotin C. Thiamine D. Pantothenic acid

Answer 42

D. Pantothenic acid Rationale: Pantothenic acid (vitamin B5) is a precursor in the synthesis of Coenzyme A (CoA), which is essential for fatty acid metabolism and other biochemical reactions.

Question 43

Which is NOT true of niacin? A. Essential factor in biosynthesis of NAD+ and NADP+ B. Has a plasma cholesterol-lowering effect C. Deficiency of niacin causes beriberi D. Derived from the catabolism of tryptophan

Answer 43

C. Deficiency of niacin causes beriberi Rationale: Deficiency of niacin causes pellagra, not beriberi. Beriberi is caused by thiamine (vitamin B1) deficiency.

Question 44

The following are macrominerals, EXCEPT: A. Phosphorus B. Potassium C. Sodium D. Fluoride

Answer 44

D. Fluoride Rationale: Fluoride is considered a trace mineral, not a macromineral. Macrominerals include phosphorus, potassium, and sodium, which are required in larger amounts.

Question 45

Which of the following tends to lower both HDL and LDL: A. Polyunsaturated fatty acids B. Saturated fatty acids C. Monounsaturated fatty acids D. None of the above

Answer 45

A. Polyunsaturated fatty acids Rationale: Polyunsaturated fatty acids (PUFAs) can lower both HDL (high-density lipoprotein) and LDL (low-density lipoprotein) cholesterol levels.

Question 46

The following are macronutrients, EXCEPT: A. Triglycerides B. Carbohydrates C. Proteins D. Vitamins

Answer 46

D. Vitamins Rationale: Macronutrients include carbohydrates, proteins, and triglycerides (fats). Vitamins are considered micronutrients.

Question 47

Factors increasing basal metabolic rate: A. 2,4-dinitrophenol B. Thyroid hormones C. Obesity D. Infancy E. All of the above

Answer 47

E. All of the above Rationale: 2,4-dinitrophenol, thyroid hormones, obesity, and infancy all increase basal metabolic rate. 2,4-dinitrophenol uncouples oxidative phosphorylation, thyroid hormones stimulate metabolism, and both obesity and infancy are associated with higher metabolic rates.

Question 48

Specific dynamic action of food: A. Energy used during digestion, absorption, and metabolism of food B. Energy needed to maintain basic physiologic functions under standard conditions C. Energy used during movement and muscle contraction D. Energy used for muscles and growth of body organs

Answer 48

A. Energy used during digestion, absorption, and metabolism of food Rationale: Specific dynamic action (SDA) refers to the energy expended in digesting, absorbing, and metabolizing food, also known as the thermic effect of food.

Question 49

Basal metabolic rate: A. Energy used during digestion, absorption, and metabolism of food B. Energy needed to maintain basic physiologic functions under standard conditions C. Energy used during movement and muscle contraction D. Energy used for muscles and growth of body organs

Answer 49

B. Energy needed to maintain basic physiologic functions under standard conditions Rationale: Basal metabolic rate (BMR) is the amount of energy required to maintain basic physiological functions such as breathing, circulation, and cell production while at rest in a thermoneutral environment and in a post-absorptive state.

Question 50

Wernicke-Korsakoff syndrome: A. Defective transketolase enzyme B. Seen primarily in alcoholics C. Masked chronic thiamine deficiency D. All of the above E. B & C only

Answer 50

D. All of the above Rationale: Wernicke-Korsakoff syndrome is characterized by a defective transketolase enzyme, is seen primarily in alcoholics, and is caused by chronic thiamine deficiency.

Question 51

TRUE of triglycerides, EXCEPT: A. Has a high satiety value B. Supply essential unsaturated fatty acids C. Serve as carriers of fat-soluble vitamins D. Provide 7 kcal/gram of energy

Answer 51

D. Provide 7 kcal/gram of energy Rationale: Triglycerides provide 9 kcal/gram of energy, not 7. They also have high satiety value, supply essential unsaturated fatty acids, and serve as carriers of fat-soluble vitamins.

Question 52

Defined as the minimum daily intake of protein needed to meet the needs for normal maintenance: A. Recommended daily dietary allowance B. Biologic value of proteins C. Protein requirement D. Protein balance

Answer 52

C. Protein requirement Rationale: The protein requirement is the minimum daily intake needed to meet the needs for normal maintenance, as opposed to the recommended daily dietary allowance, which is a higher value to ensure sufficiency for nearly all individuals.

Question 53

Examples of conditions exhibiting negative nitrogen balance, EXCEPT: A. Pregnancy B. Fasting C. Debilitating diseases D. Kwashiorkor E. Burn patients

Answer 53

A. Pregnancy Rationale: Pregnancy typically results in a positive nitrogen balance due to the increased need for protein for fetal growth. Conditions like fasting, debilitating diseases, kwashiorkor, and burn patients often result in negative nitrogen balance.

Question 54

Which is NOT an essential amino acid: A. Valine B. Lysine C. Methionine D. Tryptophan E. Alanine

Answer 54

E. Alanine Rationale: Alanine is a non-essential amino acid, meaning the body can synthesize it. Valine, lysine, methionine, and tryptophan are essential amino acids that must be obtained through the diet.

Question 55

Biotin is involved in which of the following types of reactions? A. Hydroxylations B. Carboxylations C. Decarboxylations D. Dehydrations

Answer 55

B. Carboxylations Rationale: Biotin functions as a coenzyme in carboxylation reactions, which involve the addition of a carboxyl group to substrates.

Question 56

A 3-month-old boy presents with poor feeding and growth, hypotonia, lactic acidemia, and mild acidosis. The pyruvate to lactate ratio is high, and there is decreased conversion of pyruvate to Acetyl CoA. Which of the following may be considered for therapy? A. Thiamine B. FFA C. Biotin D. Vitamin C

Answer 56

A. Thiamine Rationale: Thiamine (vitamin B1) is a cofactor for pyruvate dehydrogenase, the enzyme responsible for converting pyruvate to Acetyl CoA. Thiamine supplementation can help improve enzyme activity and reduce lactic acid buildup.

Question 57

Which of the following conditions would primarily produce a functional deficiency of Vitamin K? A. Coumadin therapy B. Broad-spectrum antibiotic C. Premature birth D. Lack of red meat in the diet

Answer 57

A. Coumadin therapy Rationale: Coumadin (warfarin) therapy inhibits the action of vitamin K, leading to a functional deficiency by preventing the synthesis of vitamin K-dependent clotting factors.

Question 58

A deficiency of vitamin B12 causes: A. Cheilosis B. Beriberi C. Pernicious anemia D. Scurvy

Answer 58

C. Pernicious anemia Rationale: Vitamin B12 deficiency results in pernicious anemia, a condition characterized by megaloblastic anemia and neurological symptoms. Cheilosis, beriberi, and scurvy are caused by deficiencies of other vitamins.

Question 59

The following is/are true of dietary fiber, except: A. Dietary fiber consists of cellulose, lignin, and pectin B. Provides approximately 7 kcal of energy from the C. Adds bulk to stool D. Can absorb 10 - 15 times its own weight in water

Answer 59

B. Provides approximately 7 kcal of energy from the Rationale: Dietary fiber is not a significant source of calories and does not provide 7 kcal of energy. It consists of cellulose, lignin, and pectin, adds bulk to stool, and can absorb water.

Question 60

Considered as the most abundant mineral in the body: A. Iron B. Chloride C. Fluoride D. Calcium

Answer 60

D. Calcium Rationale: Calcium is the most abundant mineral in the human body, primarily found in bones and teeth. Iron, chloride, and fluoride are also important minerals but are not as abundant as calcium.

Question 61

The following are considered macronutrients, except: A. Polysaccharides B. Triglycerides C. Calcium D. Amino acids

Answer 61

C. Calcium Rationale: Macronutrients include polysaccharides, triglycerides, and amino acids, which are required in large amounts. Calcium is a micronutrient, required in smaller amounts but still essential for health.

Question 62

Which of the following vitamins would most likely become deficient in a person who develops a completely carnivorous lifestyle? A. Thiamine B. Niacin C. Cobalamin D. Vitamin C

Answer 62

D. Vitamin C Rationale: Vitamin C is found primarily in fruits and vegetables. A carnivorous diet, lacking these sources, can lead to vitamin C deficiency.

Question 63

Humans most easily tolerate a lack of which of the following nutrients? A. Protein B. Iodine C. Carbohydrate D. Lipid

Answer 63

C. Carbohydrate Rationale: Humans can tolerate a lack of carbohydrates because the body can use fats and proteins for energy through gluconeogenesis and ketogenesis. Lack of protein, iodine, or lipids would have more immediate and severe effects on health.

Question 64

What is an important function of fiber? A. It adds flavor to food B. It aids in the absorption of fat-soluble vitamins C. It is an important energy source in the absence of lipids D. It can bind toxigenic substances

Answer 64

D. It can bind toxigenic substances Rationale: Dietary fiber can bind to toxigenic substances and help eliminate them from the body. It also aids in digestion, adds bulk to stool, and promotes regular bowel movements.

Question 65

If there is a dysfunction in the oxidase enzyme system (like cytochrome oxidase, ascorbic acid oxidase), which mineral is most likely affected? A. Zinc B. Chloride C. Selenium D. Copper

Answer 65

D. Copper Rationale: Copper is a crucial component of several oxidase enzymes, including cytochrome oxidase and ascorbic acid oxidase. A dysfunction in these enzymes can indicate a copper deficiency.

Question 66

After an overnight fast, a diabetic woman feels nauseous and skips breakfast but takes her insulin shot. This results in: A. Increased glycogenolysis B. Hypoglycemia C. Increased lipolysis D. Glycosuria

Answer 66

B. Hypoglycemia Rationale: Taking insulin without eating can lead to hypoglycemia because insulin promotes glucose uptake into cells, reducing blood glucose levels without replenishment from food.

Question 67

The following are true of steroid hormone action, EXCEPT: A. Hydrophobic steroid hormones bound to plasma protein carriers diffuse into the target cell B. Steroid hormone receptors are in the cytoplasm or nucleus C. The receptor-hormone complex binds to DNA and affects the genes D. Activated genes produce new mRNA that moves back into the cytoplasm

Answer 67

D. Activated genes produce new mRNA that moves back into the cytoplasm Rationale: This statement is true and describes part of the steroid hormone mechanism. All given statements are correct about steroid hormone action.

Question 68

Type I intracellular receptor: A. Glucocorticoid receptor B. Thyroid hormone receptor C. Retinoid receptor D. Vitamin D receptor

Answer 68

A. Glucocorticoid receptor Rationale: Type I intracellular receptors include glucocorticoid receptors, which are found in the cytoplasm and bind hormones like cortisol.

Question 69

Hormone that affects thyroid hormone synthesis and release: A. ADH B. TSH C. ACTH D. Prolactin

Answer 69

B. TSH Rationale: Thyroid-stimulating hormone (TSH) directly stimulates the thyroid gland to synthesize and release thyroid hormones.

Question 70

Increased reabsorption of water from the kidney is due to: A. Cortisol B. Insulin C. Vasopressin D. Glucagon

Answer 70

C. Vasopressin Rationale: Vasopressin, also known as antidiuretic hormone (ADH), increases the reabsorption of water in the kidneys, reducing urine volume and concentrating urine.

Question 71

The term used for any abnormal new growth of tissue which may be benign or malignant in nature: A. Cancer B. Neoplasm C. Malignancy D. Disease

Answer 71

B. Neoplasm Rationale: A neoplasm is an abnormal new growth of tissue, which can be benign or malignant. Cancer and malignancy specifically refer to malignant growths, while disease is a broader term.

Question 72

It is estimated that 80% of human cancers are caused by these carcinogens: A. Radiant energy B. Chemicals C. Oncogenic viruses D. None

Answer 72

B. Chemicals Rationale: The majority of human cancers are attributed to chemical carcinogens, which include a wide variety of substances like tobacco smoke, industrial chemicals, and dietary carcinogens.

Question 73

The ability of cancer to invade and spread to other tissues: A. Metastasis B. Angiogenesis C. Apoptosis D. Uncontrolled growth

Answer 73

A. Metastasis Rationale: Metastasis refers to the process by which cancer cells spread from the primary site to other parts of the body, forming secondary tumors.

Question 74

These carcinogens act by introducing novel genes into normal cells: A. Radiant energy B. Chemicals C. Oncogenic viruses D. None of the above

Answer 74

C. Oncogenic viruses Rationale: Oncogenic viruses can cause cancer by inserting their genetic material into the host cell’s DNA, introducing novel genes that can drive cancer development.

Question 75

Which statement is not associated with an enhanced risk of developing skin cancer? A. Increases with increased frequency of exposure B. Increases with increased intensity of exposure C. Increases with increased melanin content of skin D. Increases depending on the time of exposure to the sun

Answer 75

C. Increases with increased melanin content of skin Rationale: Increased melanin content in the skin actually provides some protection against UV radiation, thereby reducing the risk of skin cancer. The other factors listed (frequency, intensity, and timing of sun exposure) do increase the risk of skin cancer.

Question 76

Chemical carcinogens can be identified by their mutagenicity by the following assay/s: A. Ames assay B. Lincoln assay C. Burkitt's assay D. All are correct

Answer 76

A. Ames assay Rationale: The Ames assay is a widely used test to identify chemical carcinogens by their ability to cause mutations in the DNA of bacteria.

Question 77

Epstein-Barr virus is known to cause which malignancy? A. Hepatocellular carcinoma B. Kaposi's sarcoma C. Cervical carcinoma D. Burkitt's lymphoma

Answer 77

D. Burkitt's lymphoma Rationale: Epstein-Barr virus (EBV) is associated with several types of cancer, including Burkitt's lymphoma, nasopharyngeal carcinoma, and certain types of Hodgkin's and non-Hodgkin's lymphomas.

Question 78

These encode various proteins that drive the growth of cancer cells: A. Procarcinogen B. Proto-oncogenes C. Tumor suppressor genes D. Oncogenes

Answer 78

D. Oncogenes Rationale: Oncogenes are mutated forms of proto-oncogenes that encode proteins promoting cell growth and division, contributing to cancer development.

Question 79

These encode proteins that normally suppress cell growth but are inactivated when altered by mutations: A. Procarcinogen B. Proto-oncogenes C. Tumor suppressor genes D. Oncogenes

Answer 79

C. Tumor suppressor genes Rationale: Tumor suppressor genes encode proteins that inhibit cell growth and division. When these genes are mutated and inactivated, they lose their growth-suppressing functions, which can lead to cancer.

Question 80

Also named as the "guardian of the genome" and it is noted to be mutated in some 50% of human tumors: A. MYC B. P53 C. RAS D. RB

Answer 80

B. P53 Rationale: P53 is known as the "guardian of the genome" because of its role in preserving genomic stability by preventing mutations. It is one of the most frequently mutated genes in human cancers.

Question 81

Procarcinogens need to be activated by an enzyme to become which of the following? A. True carcinogens B. Ultimate carcinogens C. Pre-carcinogens D. All of the above

Answer 81

B. Ultimate carcinogens Rationale: Procarcinogens are substances that require metabolic activation by enzymes to become ultimate carcinogens, which are the active forms that can induce cancer.

Question 82

A mechanism of oncogene activation wherein a piece of one chromosome is split off and joined to another like in Burkitt's lymphoma: A. Promoter insertion B. Chromosomal translocation C. Gene amplification D. Enhancer insertion

Answer 82

B. Chromosomal translocation Rationale: Chromosomal translocation is a mechanism where a piece of one chromosome breaks off and attaches to another chromosome. This is a common feature in Burkitt's lymphoma.

Question 83

Abnormal multiplication of a gene resulting in many copies: A. Promoter insertion B. Chromosomal translocation C. Gene amplification D. Enhancer insertion

Answer 83

C. Gene amplification Rationale: Gene amplification refers to the process by which a cell makes many copies of a gene, leading to overexpression of the gene product, which can contribute to cancer development.

Question 84

Which is not a feature of oncogenes? A. Mutations in one of the two alleles is sufficient B. Gain of function of a protein that signals cell division C. Often with strong tissue preference D. All are correct

Answer 84

D. All are correct Rationale: All the listed features are correct descriptions of oncogenes: a single mutated allele can be sufficient for their activation, they typically involve gain-of-function mutations, and they often exhibit tissue preference.

Question 85

A family of oncogenes encoding small GTPases, initially identified in certain murine sarcoma viruses: A. MYC B. P53 C. RAS D. RB

Answer 85

C. RAS Rationale: The RAS family of oncogenes encodes small GTPases that are involved in cell signaling pathways that regulate cell growth and division. RAS genes were first identified in rat sarcoma viruses.

Question 86

A chromosomal instability wherein the chromosomal number of a cell is not a multiple of the haploid number: A. Microsatellite instability B. Aneuploidy C. Telomerase defect D. Spindle assembly defect

Answer 86

B. Aneuploidy Rationale: Aneuploidy refers to an abnormal number of chromosomes that is not an exact multiple of the haploid number, often leading to genomic instability and cancer.

Question 87

A pathologic form of cell death that is not generally programmed: A. Apoptosis B. Mutation C. Necrosis D. None of the above

Answer 87

C. Necrosis Rationale: Necrosis is a form of traumatic cell death that results from acute cellular injury and is not a programmed process like apoptosis.

Question 88

This is the effector that digests important structural proteins and is common in both the extrinsic and intrinsic pathway of apoptosis: A. Caspase-9 B. Caspase-3 C. Caspase-8 D. APAF-1

Answer 88

B. Caspase-3 Rationale: Caspase-3 is a key executioner caspase in both the extrinsic and intrinsic pathways of apoptosis, responsible for cleaving and activating various proteins that lead to cell death.

Question 89

The stimulant of angiogenesis: A. HIF-1 B. EGF C. VEGF D. PDGF

Answer 89

C. VEGF Rationale: Vascular Endothelial Growth Factor (VEGF) is a major stimulant of angiogenesis, the process by which new blood vessels form from pre-existing vessels, which is crucial for tumor growth and metastasis.

Question 90

Calcitonin is a tumor biomarker that is associated with: A. Hepatocellular carcinoma B. Myeloma C. Medullary carcinoma of thyroid D. Germ cell tumor

Answer 90

C. Medullary carcinoma of thyroid Rationale: Calcitonin is produced by the parafollicular cells (C cells) of the thyroid gland and serves as a biomarker for medullary carcinoma of the thyroid.

Question 91

Imatinib, a tyrosine kinase inhibitor, belongs to which of the following classes of drugs? A. Inhibitors of signal transduction B. Monoclonal antibodies C. Inhibitors of hormone receptors D. Anti-angiogenesis agents E. Biologic response modifiers

Answer 91

A. Inhibitors of signal transduction Rationale: Imatinib is a tyrosine kinase inhibitor that specifically targets and inhibits the BCR-ABL tyrosine kinase, thus inhibiting signal transduction pathways that promote cancer cell proliferation.

Question 92

Cells show diminished control of growth. A. Malignant Tumors B. Benign Tumors C. Both D. Neither

Answer 92

C. Both (Malignant and Benign Tumors) Rationale: Both benign and malignant tumors show diminished control of growth compared to normal cells. However, malignant tumors also have the ability to invade and metastasize.

Question 93

These do not invade the local tissue nor spread to other parts of the body. A. Malignant Tumors B. Benign Tumors C. Both D. Neither

Answer 93

B. Benign Tumors Rationale: Benign tumors grow locally without invading adjacent tissues or spreading to other parts of the body, unlike malignant tumors.

Question 94

Metastasis is generally responsible for the death of patients. A. Malignant Tumors B. Benign Tumors C. Both D. Neither

Answer 94

A. Malignant Tumors Rationale: Malignant tumors are capable of metastasis, which is the spread of cancer cells to distant parts of the body and is often responsible for cancer-related deaths.

Question 95

Proliferate rapidly and display diminished growth control. A. Malignant Tumors B. Benign Tumors C. Both D. None

Answer 95

A. Malignant Tumors Rationale: Malignant tumors proliferate rapidly and show significant loss of growth control, contributing to their aggressive behavior and potential to spread.

Question 96

A proto-oncogene can become an oncogene when: A. It is shut off B. It is translocated next to a highly expressed gene C. Growth factors decrease cell division rate D. A person is exposed to pesticides

Answer 96

B. It is translocated next to a highly expressed gene Rationale: A proto-oncogene can become an oncogene through genetic changes such as translocation, amplification, or mutation, which can lead to its overexpression and contribute to uncontrolled cell growth.

Question 97

Loss of tumor suppression in a cell usually results from: A. Cytokine activation of a tumor suppressor gene B. A translocation of a tumor suppressor gene C. An inversion involving a tumor suppressor gene D. A deletion of a tumor suppressor gene

Answer 97

D. A deletion of a tumor suppressor gene Rationale: The loss of function of tumor suppressor genes, often through deletions or mutations, results in the loss of regulation of cell growth and division, contributing to cancer development.

Question 98

The following are functions of proto-oncogenes EXCEPT: A. Intracellular growth hormones B. Transmembrane growth factors C. Intracellular signal transduction D. Intranuclear transcription factors

Answer 98

A. Intracellular growth hormones Rationale: Proto-oncogenes do not function as intracellular growth hormones. They typically encode proteins involved in growth factor signaling, signal transduction, and transcription factors that regulate cell growth.

Question 99

The following are tumor markers, EXCEPT: A. CEA (Carcinoembryonic Antigen) B. AFP (Alpha-fetoprotein) C. Norepinephrine D. Acid phosphatase (PAP)

Answer 99

C. Norepinephrine Rationale: Norepinephrine is a neurotransmitter and hormone, not a tumor marker. Tumor markers like CEA, AFP, and PAP are substances produced by cancer cells or by the body in response to cancer.

Question 100

Growth of new blood vessels in and around tumors is called: A. Invasiveness B. Angiogenesis C. Metastasis D. Dedifferentiation

Answer 100

B. Angiogenesis - Rationale: Angiogenesis is the process by which new blood vessels form, supplying nutrients and oxygen to tumors, facilitating their growth and potential to metastasize.