Basic Medical Histology (GMS6630) Unit 1 - Multiple Choice Questions

A patient with a chromosomal complement of XO has a. trisomy of the sex chromosomes b. Turner syndrome c. monosomy of the autosomes d. Klinefelter syndrome e. a male phenotype

Turner syndrome. Patients with Turner syndrome are females who lack the second X chromosomes; therefore, they are monosomal for the sex chromosomes not for the autosomes. Turner syndrome is a male phenotype with an extra X chromosome.

Which of the following methods involves immersing fixed tissue in increasing concentrations of ethanol in water? Clearing Dehydration Embedding Mounting Rehydration

Dehydration

A patient with a chromosomal complement of XXX has a. male phenotype b. female phenotype c. a very short life span d. a higher IQ than his/her siblings e. trisomy of autosomes

Female phenotype. The patient is a female who has the triple X syndrome, thus she has an extra sex chromosome rather than trisomy of the autosomes. These patients usually have a lower IQ than their siblings but have a normal life span and can even give birth to children with a normal chromosomal complement.

A male patient is seen for the first time by his physician; the patient has very thin, slender legs and unusually long, slender fingers. The patient's history indicates that he has been diagnosed with a connective tissue disorder, known as Marfan syndrome. The mutation that causes this syndrome affects a. tropomyosin b. troponin c. microfibrils d. elastin e. fibrillin

Fibrillin. Marfan syndrome is due to a mutation that involves the gene that codes for the component of elastic fibers known as fibrillin. Individuals with this condition frequently have cardiovascular problems, including aortic aneurysm, high blood pressure, dislocation of the lens of the orb. Their collagen fibers, muscle fibers, and actin filaments are normal.

The agents in which of the following procedures are intended to stabilize tissue structure by coagulating proteins and promoting cross-linking? Clearing Dehydration Embedding Fixation Mounting

Fixation

Which of the following is the site of actin and tubulin synthesis? Centrioles Free polyribosomes Mitochondria RER SER

Free polyribosomes

The clear area indicated represents the basil lucida and is rich in a. hyaluronic acid b. fibronectin c. laminin d. perlecan e. cadherins

Laminin. The clear area indicated by the tip of the arrow in this electron micrograph represents the lamina lucida component of the basal lamina. It is rich in laminin, a glycoprotein that facilitates adhesion between the basal lamina and epithelial cells. Fibronectin is located on the connective tissue side of basal lamina. Cadherins are transmembrane proteins that permit cells to contact and adhere to one another. Neither hyaluronic acid nor perlecans is located in this region.

During meiosis, some chromosomes do not separate from each other. This is called a. diplotene b. nondisjunction c. diakinesis d. zygotene e. leptotene

Nondisjunction. During the anaphase I of meiosis, the homologous chromosomes may remain attached to each other, and the two newly formed cells will have unequal chromosomal numbers. This process is known as nondisjunction. Diplotene, zygotene, diakinesis, and leptotene are phases of prophase I of the first meiotic division.

Ribosomal RNA (rRNA) is synthesized by which of the following? Free polyribosomes Nuclear envelope Nucleolus RER SER

Nucleolus

Which of the following terms is applied to the smallest chromatin subunit in eukaryotic cells? Chromosome Euchromatin Genes Heterochromatin Nucleosome

Nucleosome According to the order from smallest to largest, the order will be: Nucleotide, Gene, DNA, Chromatin, Chromatid, Chromosome.

During a routine examination of a 3-year-old child, the pediatrician notes that the color of the pupil is white and that the child is cross-eyed. She asks the father if there are any cases of retinoblastoma in the family, and, because the answer is in the affirmative, she calls in a pediatric ophthalmologist. The ophthalmologist knows that retinoblastoma is due to the mutation of the Rb gene (retinoblastoma gene) and that it is a recessive trait. Retinoblastoma can metastasize to the brain via the a. optic nerve b. superior division of the oculomotor nerve c. trochlear nerve d. abducent nerve e. inferior division of the oculomotor nerve

Optic Nerve. The retina is attached to the brain via the optic nerve; therefore, malignant cells can use the optic nerve as a passageway to the brain. The superior and inferior divisions of the oculomotor nerve, the trochlear nerve, and the abducent nerve all innervate the external muscles of the eye and do not contact the retina.

A neonatal baby boy is observed to have malformed hands, feet, and skull. Additional examination displays jaundice, hepatomegaly, and hypotonic muscles with psychomotor retardation. The pediatrician diagnoses the baby with cerebrohepatorenal syndrome (Zellweger syndrome). This condition is due to problems with which of the following organelles? a. mitochondria b. lysosomes c. early endosomes d. late endosomes e. peroxisomes

Peroxisomes. Children with cerebrohepatorenal syndrome die at an early age due to mutations in their peroxin genes that code for defective receptors that are unable to transfer enzymes destined for peroxisomes into these organelles. Mitochondria, lysosomes, and endosomes are not affected by this mutation.

Which of the following is the site of steroid hormone synthesis? Golgi complex Free polyribosomes Mitochondria RER SER

SER

Radioautography is the method of choice for revealing which of the following in a tissue section? Sites of synthesis of various molecules Molecular weights of products of cell synthesis Diameter of a secretory cell Number of copies of a particular species of mRNA Cell structure in unstained tissue sections

Sites of synthesis of various molecules

A patient who had surgery for ovarian cancer is placed on a combination of cisplatin and taxol therapy. Taxol is an antimitotic agent that a. affects microfilaments b. affects intermediate filaments c. has defective dynein d. prevents the polymerization of microtubules e. stabilizes microtubules

Stablizes microtubules. Unlike most antimitotic agents that interfere with polymerization or depolymerization of microtubules, taxol stabilizes microtubules so that they cannot shorten or lengthen. In this fashion, the mitotic spindle apparatus cannot change its length, thus preventing the movement of the chromosomes during the mitotic event. Dynein, microfilaments, and intermediate filaments are unaffected by taxol. Cisplatin: attacks the N7 reactive center on purine residues and as such can cause deoxyribonucleic acid (DNA) damage in cancer cells, blocking cell division and resulting in apoptotic cell death.

Dynein arms are always attached to one of the following. Which one is that structure? a. central sheet b. singlets c. subunit A d. subunit B e. radial spoke

Subunit A Dynein arms are microtubule-associated proteins that function in the achievement bending the cilium. These molecular motors are attached to the subunit A of the axoneme. The central sheet and the radial spokes are both composed of an elastic protein that become stretched during the "cocking" of the axoneme and, as they return to their normal length, they effect ciliary motion.

Which description refers to cadherins? a. They are peripheral proteins. b. They are associated with cell-cell adhesion. c. They are associated with adherence to the basal lamina. d. They have binding sites for heparin sulfate. e. They are associated with hemidesmosomes.

They are associated with cell-cell adhesion. Cadherins are integral proteins that are designed to assist cells to maintain contact with one another. Hemidesmosomes, heparin sulfate, and basal lamina are all associated with cell to extracellular matrix contact

Which of the following best described the appearance of a unit membrane under a transmission electron microscope? a layer of hydrophobic tails of phospholipids sandwiched between two layers of hydrophillic heads. Junctional complex Lipid bilayer Pentalaminar structure Porous structure Trilaminar structure

Trilaminar structure

An African-American patient had surgery and forms a very thick, elevated growth at the site of the skin incision. This elevated growth is known as a keloid and is due to the excessive accumulation of a. hyaluronic acid b. proteoglycans c. type I collagen d. elastic fibers e. oxytalan fibers

Type 1 collagen. African Americans are especially predisposed to the excessive accumulation of type I collagen at the site of wound healing.

The tensile strength of the healing wound about a week after the cut surfaces of the skin are sutured to each other is about 10% of the normal tensile strength of skin. The initial weakness of the dermis during wound healing is due to the material elaborated by fibroblasts to close the wound in a very rapid fashion. This material is a. type I collagen b. type II collagen c. type III collagen d. type V collagen e. type VII collagen

Type III collagen. The first collagen to be formed by fibroblasts to effect initial closure of a wound is type III collagen (reticular fibers). This slender collagen type has a very weak tensile strength and is replaced by type I collagen within 4 weeks of the injury and, at that point, the tensile strength of the healed tissue is about 80% of the tensile strength of intact skin.

The lamina densa of the basil lamina is an area that is rich in a. type I collagen b. type II collagen c. type III collagen d. type IV collagen e. type VII collagen

Type IV collagen. The lamina densa of the basal lamina is formed mostly of a network of type IV collagen. Type I collagen is the most common collagen present in the body, and it forms thick bundles of collagen fibers. Type II collagen is present in the matrix of cartilage, and type III collagen is also known as reticular fibers, a thin fibrous collagen with many sugar groups that allow it to bind silver stain. Type VII collagen is located in the lamina reticularis of the basement membrane.

A 55-year-old patient was placed on tetracycline therapy and a week later returns to the physician, indicating that the antibiotic did not alleviate his symptoms. During their conversation the physician determines that the patient took the tetracycline capsules with milk. Which of the following components of milk interfered with the action of the drug? a. calcium b. lipid c. sodium d. rennin e. potassium

The answer is a. Calcium taken within an hour of oral tetracycline ingestion interferes with the absorption of the antibiotic through the membranes of the cells lining the stomach and small intestines. Lipid, sodium, and potassium do not interfere with tetracycline absorption. Rennin, an enzyme that curdles milk protein, has no effect on the absorption of tetracycline.

How many somatic chromosomes are in a normal human karyotype? 22 23 24 44 46

44

2. A patient with asthma has difficulty breathing and is treated with albuterol, a drug that relaxes bronchiolar smooth muscles. Albuterol acts as a(n) a. cholinergic receptor antagonist b. cholinergic receptor agonist c. adrenergic receptor antagonist d. adrenergic receptor agonist e. inhibitor of kinase phosphorylases

Adrenergic(sympathetic Fight or flight) Receptor Agonist. Albuterol is an agonist that acts on beta2-adrenergic receptors, which are located mainly on the cell membranes of bronchial tissues and, therefore, do not have many side effects. If it were an antagonist, then it would cause smooth muscle constriction Cholinergic is responsible for parasympathetic( rest and relax)

The fluidity of the plasmalemma has well-established clinical significance. Which of the following molecules decreases the cell membrane fluidity? a. glycerol b. phosphate group c. cholesterol d. integral proteins e. peripheral proteins

(C) Cholesterol decreases membrane fluidity. The polar heads of phospholipids molecules are composed of glycerol, to which a positively charged nitrogenous group is attached by a negatively charged phosphate group. Unsaturated fatty acyl molecules increase membrane fluidity. Integral and peripheral proteins do not have an effect on membrane fluidity.

Which of the following histones is typically associated with the linker region of a nucleosome? H2A H2B H3 H1 H4

(C)H1: associated with the linker region, chromatin compaction, transcription regulation, nucleosome spacing and chromosome spacing H3:dynamic and long term regulation of genes H4: dynamic and long term regulation of genes

A patient with a chromosomal complement of XXY has a. trisomy of the autosomes b. Turner syndrome c. monosomy of the sex chromosomes d. Klinefelter syndrome e. a female phenotype

(D) Klinefelter syndrome. The patient has Klinefelter syndrome and exhibits a male phenotype. Because there are three sex chromosomes, this is not a monosomy or a trisomy of the autosomes. Turner syndrome is exhibited by females who lack the second X chromosome.

Which of the following form the purse-string constriction around the equator of mitotic cells? Centrioles Intermediate filaments Microfilaments Microtubules Protofilaments

(correct) Microfilaments: actin(muscle movements, cell division, and cytoplasmic streaming.) and myosin Microtubules: they provide the rigid, organized components of the cytoskeleton that give shape to many cells, and they are major components of cilia and flagella Protofilaments: parts of microfilaments Centrioles:makes microfilaments for cell division.

Prophase of meiosis I lasts a long time and is subdivided into the following five phases:

1. Leptotene. Individual chromosomes, composed of two chromatids joined at the centromere, begin to condense, forming long strands in the nucleus. 2. Zygotene. Homologous pairs of chromosomes approximate each other, lining up in register (gene locus to gene locus), and make synapses via the synaptonemal complex, forming a tetrad. 3. Pachytene. Chromosomes continue to condense, becoming thicker and shorter; chiasmata (crossing over sites) are formed as random exchange of genetic material occurs between homologous chromosomes. 4. Diplotene. Chromosomes continue to condense and then begin to separate, revealing chiasmata. 5. Diakinesis. Chromosomes condense maximally and the nucleolus disappears, as does the nuclear envelope, freeing the chromosomes into the cytoplasm.

A malignant cell of mesenchymal origin contains cytoplastic filaments composed of vimentin. Which of the following indicates the average diameter of these filaments? 5-7 nm 10-12 nm 24 nm 50-70 nm 100-120 nm

10-12 nm

Patients with sickle cell anemia possess hemoglobin S, a mutated form of hemoglobin. Hemoglobin S is a. synthesized on free ribosomes b. synthesized on the rough endoplasmic reticulum c. modified in the Golgi apparatus d. packaged in the trans-Golgi network e. stored in condensing vesicles

A.Synthesized on free ribosomes. Hemoglobin, whether normal or mutated, is present freely in the cytosol; therefore, it is synthesized on free ribosomes. Only proteins that are to be packaged are synthesized on the rough endoplasmic reticulum. Because hemoglobin is not packaged, it does not enter the Golgi apparatus.

Which of the following structures are organelles formed by the fusion of primary lysosomes and phagosomes and also sites of active digestion of phagocytosed materials? Autophagosomes Heterophagosomes Secondary lysosomes Polysomes Residual bodies

Autophagosomes are formed by the fusion of phagosomes (containing worn-out and damaged cell organelles within the same cell) with lysosomes (containing digestive enzymes). The cell marks with ubiquinone when it) Heterophagosomes are formed by the fusion of phagosomes (containing outside material like food particles) and lysosomes (containing digestive enzymes) Secondary lysosomes(Secondary lysosomes - are formed when primary lysosomes fuse with phagosomes/pinosome (they are also referred to as endosomes). Polysomes: consist of mRNAs occupied by two or more ribosomes Residual bodies: In lysosomal digestion, residual bodies are vesicles containing indigestible materials.

Acid hydrolases are synthesized on the rough endoplasmic reticulum and are delivered to the Golgi complex to be packaged and distributed to their final destination. Patients whose protooncogenes have mutated to form ras protein related products known as ADP-ribosylation factor (ARF) may interfere with a. coatomer II (COP II) synthesis b. coatomer II (COP II) assembly c. coatomer II (COP II) dissociation from vesicles d. clathrin synthesis e. clathrin assembly

B.Coatomer II (COP II) assembly. Delivery of proteins manufactured on the rough endoplasmic reticulum to the Golgi complex is accomplished in COP II-coated vesicles. ARF catalyzes the assembly of COP II molecules to form coatomer on the cytoplasmic aspect of these transfer vesicles. Synthesis of COP II proteins as well as the disassembly of the coatomer is not influenced by ARF. Clathrin coats mediate the endocytotic pathway as well as the pathway that leads away from the trans-Golgi network.

An elderly patient is seen by his dermatologist because he developed itching and blisters of his skin. If the blistering involves the region indicated by the arrow in this electron micrograph and if the patient is shown to have IgG along the same area indicated by the arrows, the patient is probably suffering from a. dermatitis herpetiformis b. atopic dermatitis c. pemphigus vulgaris d. pemphigus foliaceus e. bullous pemphigoid

Bullous pemphigoid. Bullous pemphigoid is a relatively rare autoimmune condition occurring in elderly patients in which the patient produces IgG against his or her hemidesmosomes and separation of the epidermis from the dermis by the formation of blisters. Dermatitis herpetiformis is similar to bullous pemphigoid in that the vesicles form at the interface of the epidermis and dermis and is accompanied by itching. However, the condition begins at the highest points of the dermal ridges, and it is only later that the entire epidermal-dermal interface becomes involved. The main difference is that IgA rather than IgG is the antibody involved. Pemphigus vulgaris and pemphigus foliaceus are both blistering conditions; however, the blister is intraepidermal and involved autoantibodies against desmosomes. Atopic dermatitis is more prevalent in children than in adults and is usually located at the joints where flexion occurs. It is accompanied by edema, a thicker than normal epidermis, and excessive development of the rete apparatus.

Which of the following pairs of cellular structures regulate the distribution of membranous vesicles and organelles through their influence on microtubule polymerization? Centrioles and satellite bodies Chromosomes and mitotic spindles Cilia and flagella Golgi apparatus and endosomes Laminal and intermediate filaments

Centrioles and satellite bodies

Which of the following procedures entails impregnating a specimen with a solvent of the embedding medium? Clearing Dehydration Fixation Mounting Rehydration

Clearing

Which of the following is the most characteristic type of intermediate filament protein found in epithelial cells? Actin Cytokeratin Desmin Glial fibrillary acidic protein Integrin

Cytokeratin(type of protein found on epithelial cells, which line the inside and outside surfaces of the body. Cytokeratins help form the tissues of the hair, nails, and the outer layer of the skin.) Actin (a protein that forms (together with myosin) the contractile filaments of muscle cells, and is also involved in motion in other types of cell.) Desmin is a subunit of intermediate filaments in cardiac muscle, skeletal muscle, and smooth muscle tissue. Glial fibrillary acidic protein (involved in controlling the shape, movement, and function of astroglial cells.) integrin (subunits span the cell membrane, regulate cellular growth, proliferation, migration, signaling, and cytokine activation and release and thereby play important roles in cell proliferation and migration, apoptosis, tissue repair, as well as in all processes critical to inflammation, infection, and angiogenesis.)

A patient with leukocyte adhesion deficiency will have a/an a. autosomal dominant disorder b. sex-linked chromosomal disorder c. dysfunctional adhesins d. dysfunctional integrins e. dysfunctional cadherins

Dysfunctional integrins. Leukocyte adhesion deficiency is an autosomal recessive disorder that results in the inability of white blood cells to synthesize the beta chains of their integrin molecules. Therefore, the leukocytes are incapable of adhering to the endothelial cells and are unable to migrate to the site of inflammation. Patients with this disease have difficulties resisting bacterial infections. Adhesins are surface antigens of many microorganisms that permit them to adhere to mammalian cell surfaces, whereas cadherins are responsible for cell-cell adhesions.

A 12-year-old child complains to his physician that he frequently dislocates his joints. Upon examination, the physician notes that the patient has hyperextensive joints, has highly stretchable skin, and has kyphoscoliosis (hump back). The doctor should suspect a. scurvy b. Ehlers-Danlos syndrome c. Marfan syndrome d. cutis laxa e. mucopolysaccharidosis

Ehlers-Danlos syndrome. The doctor should suspect Ehlers-Danlos syndrome because individuals with this genetic disorder have very flexible joints, occasional kyphoscoliosis, and skin that can be stretched a couple of inches, and upon release, the skin returns to its previous position. A patient with scurvy would be recognized by bleeding gums and possible disfiguration of the long bones of the leg. Patients wtih Marfan syndrome are usually tall and thin and possess especially long fingers. Cutis laxa is characterized by stretchy skin that hangs loosely in folds. Patients with mucopolysaccharidosis die at a very young age.

Which of the following is true of the Barr body? Attaches to the inner surface of the plasma membrane during interphase Is composed of euchromatin during the mitotic phase of the cell cycle Its DNA replicated during every other cell cycle in normal males In normal females, it is a member of a homologous chromosome pair Occurs when homologous chromosomes fail to separate during anaphase

In normal females, it is a member of a homologous chromosome pair Barr body are in active X chromsomes

Which of the following is the location of the electron-transport system? Cristae Inner mitochondrial membrane Intracristal space Matrix granules Outer mitochondrial membrane

Inner mitochondrial membrane

Which of the following are composed primarily of actin or actin-like proteins? Basal bodies Cilia Cytochalasins Intermediate filaments Microfilaments

Intermediate filaments: provide mechanical support for the plasma membrane where it comes into contact with other cells or with the extracellular matrix. Microfilaments: actin and myosin Cilia: short hairlike vibrating found in epithelium and colon Cytochalasins:It inhibits cytoplasmic division by blocking the formation of contractile microfilaments Basal body: an organelle that forms the base of a flagellum or cilium.

Which of the following substances characteristically increases in abundance with increasing age in terminally differentiated cells such as neurons and muscle? Cyclin Desmin Lipofuscin Osmium Phalloidin

Lipofuscin

Ribosomes are not found in mature red blood cells. From this fact and from knowledge of ribosome function and distribution which of the following can be deducted? Mature red blood cells are incapable of protein synthesis Red blood cells lack nucleoli throughout their life cycle Mature red blood cells lack cytoplasmic enzymes Mature red blood cells contain inactive RER Mature red blood cells contain smooth ER

Mature red blood cells are incapable of protein synthesis

A 20-year-old man presenting with deteriorating vision in both eyes, especially his central vision, seeks help from his ophthalmologist. The patient also evidences cardiac dysrhythmia and an apparent demyelination of the optic nerve. The ophthalmologist suspects Leber hereditary optic neuropathy, a condition caused by a point mutation that is not X-linked but is transmitted only by females. This condition is due to problems with which of the following? a. lysosomes b. early endosomes c. late endosomes d. mitochondria e. peroxisomes

Mitochondria. Leber hereditary optic neuropathy is due to a point mutation on the mitochondrial DNA. Because the spermatozoon does not contribute mitochondria to the zygote, only the female can transmit this condition to her offspring. Lysosomes, peroxisomes, early and late endosomes do not possess DNA.

Which of the following is the location of Krebs cycle enzymes and mitochondrial DNA? Cristae Inner mitochondrial membrane Intracristal space Matrix granules Mitochondrial matrix

Mitochondrial matrix

Because of the frequent presence of ribosomes on its outer surface, the nuclear envelope may be considered a specialized portion of which organelle? Golgi complex Nucleolus Plasma membrane RER SER

RER

A 9-month-old female Jewish baby, whose parents were born in Poland, is seen by her pediatrician because of neurological problems, including generalized paralysis and blindness. The pediatrician should suspect that the child has a. spina bifida b. cranial nerve X (vagus nerve) disorder c. Tay-Sachs disease d. Fabry disease e. Refsum disease

Tay-Sachs disease. Tay-Sachs disease affects mostly children of Eastern European Jewish ancestry as well as in certain families in Louisiana of Cajun ancestry. Children with this lysosomal storage disease cannot catabolize GM2 gangliosides that accumulate in their lysosomes, and the enlarged lysosomes interfere with cell function. The interference is most problematic in the neurons of the central nervous system and causes death by the third year of life. Neither spina bifida nor vagus nerve disorders would cause generalized paralysis or blindness. Fabry disease, although a lysosomal-storage, is due to an X chromosomal defect and affects males only. Refsum disease is due to the accumulation of phytanic acid, a by-product of chlorophyll metabolism and affects older children who already eat fresh fruits and vegetables. Spina bifida: It occurs when a developing baby's spinal cord fails to develop or close properly while in the womb. Fabery disease:People who have Fabry disease don't have the enzymes that break down lipids or fats. These fats collect in blood vessels and tissue, raising the risk of heart attack, stroke and kidney failure. Refsum disease:rare genetic disease that causes weakness or numbness of the hands and feet

A patient suffering from asthma has difficulty breathing and is treated with albuterol and ipratropium, drugs that relax bronchiolar smooth muscles. Ipratropium acts as a(n) a. cholinergic receptor antagonist b. cholinergic receptor agonist c. adrenergic receptor antagonist . d. adrenergic receptor agonist e. inhibitor of kinase phosphorylases

The answer is a. Ipratropium is a cholinergic receptor antagonist and interferes with the binding of acetylcholine, a neurotransmitter, to its receptor sites on the cell membrane, thus preventing the contraction of bronchiolar smooth muscle. The two drugs are used in combination agonist-antagonist therapy to have the desired effect of maintaining an open airway.

Early in the morning, a male patient sees his physician because he and his wife have been trying to start a family. According to the patient, his wife was told that she is able to become pregnant, and he wants to have the physician check him for sterility. The physician notices that the patient has a heavy cough. Upon questioning, the patient reveals that he also coughs in the evening, produces a lot of sputum, and has had numerous colds and even occasional pneumonia. The doctor asks for a sperm sample but already is thinking of a possible diagnosis of Kartagener's syndrome, a genetic disorder that affects a. a number of keratins b. microtubule-associated proteins c. thin filaments d. intermediate filaments e. thick filaments

The answer is b. Kartagener's syndrome is due to an autosomal recessive disorder that affects ciliary motion because a microtubule-associated protein, dynein, is either defective or not present. The tubulins of microtubules are formed normally and microtubule assembly, per se, is not affected. Thin filaments, thick filaments, and intermediate filaments are not affected in Kartagener's syndrome.

.A six-month-old baby boy, when seen by his pediatrician,, exhibits an enlarged tongue and an enlarged liver. Additionally, the baby has problems with swallowing. The pediatrician should suspect that the child is suffering from a. cranial nerve X (vagus nerve) disorder b. Pompe's disease c. McArdle's syndrome d. Tay-Sachs disease e. Tarui's disease

The answer is b. Pompe's disease is a lethal glycogen-storage disease that affects infants and usually causes death by the second or third year of life. The baby is missing lysosomal acid maltase, and as glycogen accumulates in the lysosomes of the liver, heart, and some skeletal muscles, these organs enlarge. Although cranial nerve X distributes through much of the body, its malfunction does not cause any of the symptoms present in this infant . McArdle's syndrome(also known as glycogen storage disease type V (GSDV), is characterized by exercise intolerance, the second wind phenomenon, and high serum creatine kinase activity.) has an adult-onset, the symptoms of Tarui's disease usually are noted only after vigorous physical exercise. (deficiency is a glycogen storage disorder (GSD). It is rare and is inherited as an autosomal recessive disorder.)Muscle pain and fatigue on everyday activity and exercise. Fixed contractures with rhabdomyolysis. Tay-Sachs disease. (It's caused by the absence of an enzyme that helps break down fatty substances. These fatty substances, called gangliosides, build up to toxic levels in the child's brain and affect the function of the nerve cells.)

The component of the erythrocyte cell membrane that is the most essential in maintaining its biconcave disc shape is a. glycophorin b. spectrin c. ankyrin d. actin e. band 3 protein

The answer is b. Spectrin is a rod-shaped tetramer that, in association with actin and adducin, forms a hexagonal lattice that underlies the cytoplasmic surface of the red blood cell plasmalemma. Ankyrin and band 3 protein and band 1 protein anchor the hexagonal lattice to the cell membrane. Glycophorins and band 3 proteins are transmembrane proteins.

The binding of cyclin B to CDK1 (cyclin-dependent kinase 1) permits the cell to progress from a. S phase into G2 phase b. G2 phase into M phase c. G1 phase into G2 phase d. G1 phase into S phase e. prometaphase into metaphase

The answer is b. The formation of the cyclin B-CDK1 complex allows the cell to enter the mitotic cycle—that is, progress from the G2 phase into the M phase. The cell cycle cannot go from G1 to G2 directly; it has to go through the S phase first. Cyclins D and E are required to enter S from G1. Cyclins A and B are both required for the entry from the S phase into the G2 phase.

A patient with Alport's syndrome is usually a male who presents with poor kidney function and blood in the urine. The mutation causing this syndrome involves the gene for the α-3 chain of type IV collagen. The reason why the patient is usually a male is that a. males tend to get more urinary tract infections than females b. the gene forα-3 chain of collagen is located on the Y chromosome c. the gene for α-3 chain of collagen is located on the X chromosome d. the gene for α-3 chain of collagen is located on chromosome 21 of males e. hypertrophy of the prostate in elderly males exacerbates the incidence of kidney infections

The answer is c. Although the Alport's syndrome gene is recessive, its location on the X chromosome causes it to be expressed in all males, whereas in females the dominant normal gene is able to ensure the synthesis of normal α-3 chain of type IV collagen. Females actually have a greater incidence of urinary tract infection than do males; however, Alport's syndrome is a hereditary disorder and infections do not play a part in its expression. Prostatic hypertrophy does not influence the presence of Alport's syndrome.

A patient with lymphoma that involves his small intestines is treated with various chemotherapeutic agents, including vincristine. This antimitotic substance acts on a. α-actinin b. dynein c. tubulin d. myosin I e. actin

The answer is c. Vincristine interferes with polymerization of microtubules and halts mitosis, thus killing dividing cells. Vincristine has no effect on α-actinin, dynein, myosin I, or actin.

the collecting tubule of the kidney, water enters the lumen via a. pinocytosis b. endocytosis c. aquaporins d. ion channels e. carrier proteins

The answer is c. Water leaves the cells of the collecting tubule to enter its lumen by way of structures known as aquaporins. Pinocytosis and endocytosis both refer to substances entering the cell. Ion channels are designed to carry ions along a concentration gradient in or out of a cell, whereas carrier proteins can move ions as well as small molecules along and/or against a concentration gradient.

A patient with Kartagener's syndrome has a genetic disorder that is known to a. affect microfilaments b. affect intermediate filaments c. have defective dynein d. have defective kinesin e. have defective α-tubulin

The answer is c.Kartagener syndrome results from hereditary defects in the ciliary dynein that would normally provide the energy for ciliary bending. Thus, ciliated cells without functional dynein are prohibited from functioning. Persons having this syndrome are susceptible to lung infections because their ciliated respiratory cells fail to clear the tact of debris and bacteria. Additionally, males with this syndrome are sterile because their sperm are immotile

A two-week-old infant was seen by her pediatrician because of blistering of the fingers and the back of her hands. The blisters were quite large and the results of the biopsy indicated that blistering occurred in the basal layer of the epidermis. The diagnosis was epidermolysis bullosa simplex. This disease is caused by mutations in the a. tubulins b. neurofilaments c. G actins d. keratins e. chondroitins

The answer is d. Blistering in infants that occurs on the regions of the skin that are exposed to friction and pressure is a result of mutations in types 14 and 5 keratins. Tubulins, neurofilaments, G actins, and chondroitins are not affected.

A 77-year-old female is having problems sleeping, and her physician prescribed flurazepam, a sleep aid. The patient reports that she feels "groggy" for about 2 days after having taken the drug. Flurazepam is a. destroyed by the acidic conditions in the stomach b. inactivated by pepsin in the stomach c. denatured by trypsin in the duodenum d. inactivated by the P-450 enzyme system of the liver e. destroyed by proteasomes in the jejunum

The answer is d. Many drugs are inactivated by the P-450 enzyme system of the liver. In this patient the level of this enzyme system is depressed; therefore, flurazepam is not inactivated in 18 hours, as in most patients, but has a longer half-life, which accounts for the groggy feeling even 2 days later. Flurazepam is not affected by HCl, pepsin, or trypsin, nor does it enter the proteasome system of the cell.

A patient who is unable to metabolize long-chain fatty acids has problems involving her a. early endosomes b. late endosomes c. lysosomes d. peroxisomes e. proteasomes

The answer is d. Peroxisomes function in the catabolism of long-chain fatty acids, in detoxifying noxious agents, and in killing bacteria. Early and late endosomes are organelles that participate in the endocytic and endolysosomal pathways, whereas proteasomes function in the catabolism of proteins

the structure at the tip of the arrow is responsible for which of the following? a. synthesis of ATP b. assembly of microtubules c. assembly of neurofilaments d. synthesis of lysosomal proteins e. assembly of neurotubules

The answer is d. The large cell in the center of this field is a multipolar neuron in the gray matter of the spinal cord. The arrow is pointing to a structure known as a Nissl body, which was noted by electron microscopy to be composed of rough ER, the region where proteins that are to be packaged, such as lysosomal proteins, are synthesized where as microtubules (also known as neurotubules) and neurofilaments are assembled in the cytoplasm, but not involving the rough ER.

the core of the structures at the arrow tip is composed of a. thin filaments b. intermediate filaments c. thick filaments d. microtubules e. actin filaments

The answer is d. The photomicrograph depicts a pseudostratified, ciliated columnar epithelium and the structures at the arrow tip are cilia. The core of each cilium is consists of an axoneme. Axonemes are composed of nine doublet microtubules surrounding two central singlet microtubules. Thin filaments (actin filaments) constitute the core of microvilli. Intermediate filaments and thick filaments are not associated with cilia.

the cell at the tip of the pointer is in which of the following phases of mitosis? a. prophase b. prometaphase c. metaphase d. anaphase e. telophase

The answer is d. The sister chromatids of this cell are being pulled apart to proceed toward the opposite poles of the cell; therefore, this cell is in anaphase.

Integrins are associated with which of the following structures? a. zonula occludens b. zonula adherens c. fascia occludens d. desmosomes e. hemidesmosomes

The answer is e. Integrins are transmembrane proteins that are restricted to interact with the extracellular matrix. In epithelial cells they are localized in the basal surfaces and assist hemidesmosomes in adhering to the basal lamina. They do not participate in cell-to-cell contact, and all the other choices involve intracellular contact.

A patient with cancer possesses cells that are undergoing mitosis at a very rapid rate. The contractile rings that are formed during cytokinesis are composed of thin filaments intermediate filaments thick filaments microtubules neurofilaments

The answer is thin filaments. Contractile rings, composed of thin (actin) filaments form around the site where the cleavage furrow forms during telophase. Just prior to complete separation of the two daughter cells, the midbody forms, which is then incorporated into one of the two cells. Intermediate filaments, thick filaments, and neurofilaments (intermediate filaments of neurons) do not participate in the formation of contractile rings. The midbody is composed of polar microtubules and a bridge of cytoplasm.

A 2-month-old baby is brought to be examined, and the physician notices that he has flaccid muscles, a smaller head than usual, a large tongue, a short nose, and a broad face. The parents say that the baby is very quiet and hardly ever cries. The pediatrician suspects aneuploidy. The child probably has which of the following chromosomal configurations? a. Monosomy b. Trisomy c. Normal diploid complement d. Haploid complement e. Tetraploid complement

Trisomy. The baby most probably has trisomy 21, Down syndrome, in which chromosome 21 is present instead of two chromosomes, one from the mother and the other from the father. During meiosis, nondisjunction occurs, so that one cell has the extra chromosome 21 and the other cell is monosomic; that is, it is missing chromosome 21

A 9-month-old baby is seen by her pediatrician, who notices a lack of weight gain in the infant as well as thin, knobby joints. The parents tell the physician that they are making their own baby food and that the child has been very irritable and cries a lot when she is crawling on the floor. The baby's gums appear to be overly red. The pediatrician suspects lack of vitamin C in the baby's diet and recommends that the parents switch to commercially prepared baby foods and urges them to offer the child citrus fruits. Additionally, the child is to receive high doses of vitamin C for 7 days and a lower dose for an additional 30 days. Vitamin C is necessary for the synthesis of normal a. elastin b. fibrillin c. tropocollagen d. troponin e. hyaluronic acid

Tropocollagen. Vitamin C is necessary for the hydroxylation of proline residues. Hydroxyproline is required to hold the alpha chains of tropocollagen molecules to each other. The synthesis of elastin, fibrillin, and hyaluronic acid are not affected by vitamin C. Troponin is a protein present in skeletal and cardiac muscle and is not affected by the lack of vitamin C.

During a routine examination of a 3-year-old child, the pediatrician notes that the color of the pupil is white and that the child is cross-eyed. She asks the father if there are any cases of retinoblastoma in the family, and, because the answer is in the affirmative, she calls in a pediatric ophthalmologist. The ophthalmologist knows that retinoblastoma is due to the mutation of the Rb gene (retinoblastoma gene) and that it is a recessive trait. Not all cases of retinoblastoma have a familial component. There is the sporadic form of retinoblastoma in which the child's normal genetic complement does not predispose the child to have retinoblastoma. If this child had the sporadic form of retinoblastoma, then a. one copy of the Rb genes mutated b. both copies of the Rb genes mutated c. the patient's future children will most probably have one mutated Rb gene d. the patient's future children will most probably have two mutated Rb genes e. the mutated Rb gene is known as a proto-oncogene

both copies of the Rb genes mutated. Because retinoblastoma is a recessive trait, both copies of the Rb gene would have to have mutated. The normal gene, which codes for the Rb protein is known as a proto-oncogene, whereas its mutated form is known as an oncogene. Because the mutations did not occur in the gametes, the patient's future children will not have any mutated Rb genes.

A patient whose symptoms include discolored, violet-colored skin with large blisters, fever, malaise, rapid heart rate, and a great deal of pain is diagnosed with necrotizing fasciitis. The rapid spread of Staphylococus aureus and group A streptococci that ravage the connective tissue of this patient is due to the ability of these organisms to destroy one of the components of the extracellular matrix of the skin. Which is this component? a. hyaluronic acid b. keratan sulfate c. dermatan sulfate d. heparan sulfate e. chondroitin-4-sulfate

hyaluronic acid. Hyaluronic acid is a very large glycosaminoglycan that is not sulfated and is not bound to a protein core. It is able to bind a very large number of proteoglycans, thus forming a very large molecule with an enormous domain. This very large macromolecule complex is responsible for the "gel state" of the extracellular matrix. Staphylococus aureus and group A streptococci possess hyaluronidase that cleaves hyaluronic acid and converts the gel to a "sol (soluble) state," making it much easier for the microorganisms to spread very rapidly through the connective tissue element, destroying the tissues in its path. Some call these microorganisms, flesh-eating bacteria. The other four glycosaminoglycans are much smaller and, by binding to a protein core, form proteoglycans. They are not large enough by themselves to form a gel.

Which RNA synthesis is catalyzed by RNA polymerase II? a. tRNA b. rRNA that codes for the large ribosomal subunit c. rRNA that codes for the small ribosomal subunit d. mRNA e. tRNA that carries the start codon

mRNA. RNA polymerase II catalyzes the synthesis of messenger RNA (mRNA). The synthesis of all tRNA is catalyzed by RNA polymerase III, whereas all rRNA synthesis is catalyzed by RNA polymerase I.

1. Which of the following techniques is most commonly used to locate glyscogen in cells? Methylene blue staining Feulgen's reaction Periodic acid-Schiff (PAS) reaction Enzyme histochemistry Immunohistochemistry

methylene blue staining stains blood films/smears used in cytology and to stain RNA or DNA for viewing under the microscope or on hybridization membranes Feulgens reaction (the development of brilliant purple color by DNA in a microscopic preparation stained with a modified Schiff's reagent.) Periodic acid-Schiff (PAS) reaction (detect glycogen deposits in the liver when glycogen storage disease is suspected) Enzyme Histochemistry (is used to demonstrate the activity of enzymes present on tissues) Immunohistochemistry (Immunohistochemical techniques detect antigens in tissue sections by means of immunological and chemical reactions.)

Chiasmata formation a. occurs during metaphase II b. results in the exchange of genetic material between non-homologous chromosomes c. occurs during the pachytene phase d. results in nondisjunction e. results in the formation of the synaptonemal complex

occurs during the pachytene phase. Chiasmata formation occurs during the pachytene phase of prophase I of the first meiotic event. Homologous pairs of chromosomes line up during the zygotene phase of prophase I, forming the synaptonemal complex, thus permitting crossing over to occur during the pachytene phase so that there could be a random exchange of genetic material that contributes to a more diverse gene pool. Nondisjunction occurs when the homologous pairs of chromosomes separate during anaphase I.