# Cotton wool appearance is seen in:

 # Cotton wool appearance is seen in:

A. Paget’s disease

B. Osteomyelitis

C. Fibrous dysplasia

D. Achondroplasia

The correct answer is A. Paget's disease.

The radiographic appearance of chronic diffuse sclerosing osteomyelitis is, as the name suggests,

that of a diffuse patchy, sclerosis of bone often described as ‘cotton-wool’ appearance. This radiopaque lesion may be extensive and is sometimes bilateral. In occasional cases, there is bilateral involvement of both the maxilla and the mandible in the same patient. Because of the diffuse nature of the disease, the border between the sclerosis and the normal bone is often indistinct. The pattern may actually mimic Paget’s disease of bone or cemento-osseous dysplasia.

Reference: Shafer's 

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Pathological calcification is seen in:

 # Pathological calcification is seen in:

A. Scleroderma

B. Lichen planus

C. Dystrophic epidermolysis bullosa

D. Lupus erythematosus

The correct answer is A. Scleroderma.

Pathologic calcification is a common process in a wide variety of disease states; it implies the abnormal deposition of calcium salts, together with smaller amounts of iron, magnesium, and other minerals. When the deposition occurs in dead or dying tissues, it is called dystrophic calcification; it occurs in the absence of derangements in calcium metabolism (i.e., with normal serum levels of calcium). In contrast, the deposition of calcium salts in normal tissues is known as metastatic calcification and is almost always secondary to some derangement in calcium metabolism (hypercalcemia). Of note, while hypercalcemia is not a prerequisite for dystrophic calcification, it can exacerbate it.

Systemic sclerosis can be classified into two groups on the basis of its clinical course:

• Diffuse scleroderma, characterized by initial widespread skin involvement, with rapid progression and early visceral involvement

• Limited scleroderma, with relatively mild skin involvement, often confined to the fingers and face. Involvement of the viscera occurs late, so the disease in these patients generally has a fairly benign course. This clinical presentation is also called the CREST syndrome because of its frequent features of calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia.

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# Non disjunction of chromosome occurs in which stage?

 # Non disjunction of chromosome occurs in which stage?

A. Prophase

B. Metaphase

C. Anaphase

D. Telophase

The correct answer is C. Anaphase.

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division (mitosis/meiosis). There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during mitosis.

Meiosis II

Ovulated eggs become arrested in metaphase II until fertilization triggers the second meiotic division. Similar to the segregation events of mitosis, the pairs of sister chromatids resulting from the separation of bivalents in meiosis I are further separated in anaphase of meiosis II. In oocytes, one sister chromatid is segregated into the second polar body, while the other stays inside the egg. During spermatogenesis, each meiotic division is symmetric such that each primary spermatocyte gives rise to 2 secondary spermatocytes after meiosis I, and eventually 4 spermatids after meiosis II. Meiosis II-nondisjunction may also result in aneuploidy syndromes, but only to a much smaller extent than do segregation failures in meiosis I. 

Mitosis

Division of somatic cells through mitosis is preceded by replication of the genetic material in S phase. As a result, each chromosome consists of two sister chromatids held together at the centromere. In the anaphase of mitosis, sister chromatids separate and migrate to opposite cell poles before the cell divides. Nondisjunction during mitosis leads to one daughter receiving both sister chromatids of the affected chromosome while the other gets none. This is known as a chromatin bridge or an anaphase bridge. Mitotic nondisjunction results in somatic mosaicism, since only daughter cells originating from the cell where the nondisjunction event has occurred will have an abnormal number of chromosomes. Nondisjunction during mitosis can contribute to the development of some forms of cancer, e.g., retinoblastoma. Chromosome nondisjunction in mitosis can be attributed to the inactivation of topoisomerase II, condensin, or separase. Meiotic nondisjunction has been well studied in Saccharomyces cerevisiae. This yeast undergoes mitosis similarly to other eukaryotes. Chromosome bridges occur when sister chromatids are held together post replication by DNA-DNA topological entanglement and the cohesion complex. During anaphase, cohesin is cleaved by separase. Topoisomerase II and condensin are responsible for removing catenations. 

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Mediators of inflammation are all EXCEPT:

 # Mediators of inflammation are all EXCEPT:

A. TNF

B. IFN

C. PG

D. Myeloperoxidase

The correct answer is D. Myeloperoxidase.

Myeloperoxidase is not an inflammatory mediator. It is an enzyme in neutrophils that convert Cl-, I- and SCN- ions to corresponding acids -HOCl etc. These acids are potent oxidants and help in destroying the invading organisms. 

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Complication of duodenal ulcer:

 # Complication of  duodenal ulcer: 

A. Hypoacidity

B. Pernicious anemia

C. Stenosis

D. Malignant transformation

The correct answer is C. Stenosis.

Obstruction from edema or scarring occurs in about 2% of the patients. Most often due to pyloric channel ulcers. May also occur with duodenal ulcers.

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Gluconeogenesis occurs in the liver and:

 # Gluconeogenesis occurs in the liver and ________.

 A. Kidney

 B. Muscle

 C. Heart

 D. Fat

The correct answer is A. Kidney.

Gluconeogenesis (GNG) is a metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon structures. 

In vertebrates, gluconeogenesis occurs mainly in the liver and, to a lesser extent, in the cortex of the kidneys. It is one of two primary mechanisms – the other being degradation of glycogen (glycogenolysis) – used by humans and many other animals to maintain blood sugar levels, avoiding low levels (hypoglycemia). Although most gluconeogenesis occurs in the liver, the relative contribution of gluconeogenesis by the kidney is increased in diabetes and prolonged fasting.

Gluconeogenesis is a pathway consisting of a series of eleven enzyme-catalyzed reactions. The pathway will begin in either the liver or kidney, in the mitochondria or cytoplasm of those cells, this being dependent on the substrate being used. Many of the reactions are the reverse of steps found in glycolysis. 

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Fluid mosaic model of membrane structure was proposed by:

 # Fluid mosaic model of membrane structure was proposed by:

A. Watson and Crick

B. Edward H. Angle

C. G.V. Black

D. Singer and Nicolson

The correct answer is D. Singer and Nicolson.

The fluid mosaic model explains various observations regarding the structure of functional cell membranes. According to this biological model, there is a lipid bilayer (two molecules thick layer consisting primarily of amphipathic phospholipids) in which protein molecules are embedded. The phospholipid bilayer gives fluidity and elasticity to the membrane. Small amounts of carbohydrates are also found in the cell membrane. The biological model, which was devised by SJ Singer and G. L. Nicolson in 1972, describes the cell membrane as a two-dimensional liquid that restricts the lateral diffusion of membrane components. 

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