Human Genetics and Disorders

Gaucher's disease is a lysosomal storage disorder caused by deficiency of the enzyme glucocerebrosidase, leading to accumulation of glucocerebroside (a type of lipid or fat) in cells. This results in abnormal fat metabolism, specifically affecting the breakdown of sphingolipids. It is not primarily a disorder of protein, carbohydrate metabolism, or vitamin deficiency.

BRCA1 is indeed a tumor suppressor gene that maintains genomic integrity by preventing uncontrolled cell proliferation. The multifunctional BRCA1 protein participates in crucial cellular processes including DNA damage repair, ubiquitination, and transcriptional regulation. Mutations in this gene are well-established risk factors for hereditary breast, ovarian, and prostate cancers, making all three statements factually correct.

Fragile X Syndrome is caused by the loss of the FMR1 gene, which produces FMRP (Fragile X Mental Retardation Protein). FMRP acts as a translational regulator or 'brake' on protein synthesis in neurons, particularly at synapses. When FMRP is absent, there is excessive protein production leading to the cognitive and behavioral symptoms associated with Fragile X Syndrome. Note: The question has a typo - 'Foregile' should be 'Fragile'.

This is the correct option. Down syndrome is an example of inherited disease. It occurs when an individual has a full or partial extra copy of chromosome 21.

Alexander's disease (a leukodystrophy caused by GFAP mutations) classically presents with extensive white matter involvement and characteristic frontal-predominant changes, with MRI showing hyperintense lesions that commonly involve the thalami and basal ganglia. The pattern of extensive deep white matter hyperintensity with thalamic involvement is highly suggestive of Alexander disease, differentiating it from other leukodystrophies which have different distribution patterns.

Bladder exstrophy carries the highest risk of urothelial cancer among urogenital anomalies due to chronic inflammation and prolonged exposure of urothelium to urine. The other conditions (medullary sponge kidney, renal agenesis, double ureter) do not significantly increase urothelial cancer risk.

Leukotrichia (white hair in vitiligo patches) indicates destruction of melanocytes in hair follicles, which is a POOR prognostic sign as it means vitiligo is more stable and resistant to treatment. All other statements are true: vitiligo has genetic predisposition, UVB therapy is a mainstay treatment, and local steroids are used. The question asks which is NOT true.

This is true during fertilization.

Rh-positive blood type is an autosomal dominant trait; inheritance of one Rh+ allele results in Rh-positive phenotype. The other options are all recessive X-linked traits: color blindness, albinism (oculocutaneous), and hemophilia A/B require two X chromosomes with the recessive allele (or one in males) to be expressed.

Achondroplasia is an autosomal dominant disorder. When healthy (normal height) parents produce a child with achondroplasia, it results from a spontaneous (new) mutation in the gametes or early embryo. Point mutation is a type of mutation mechanism, while induced mutation refers to artificially caused changes.

Albinism is caused by defective melanin production due to deficiency of the enzyme tyrosinase (also called tyrosine 3-monooxygenase). This enzyme converts tyrosine to DOPA in the melanin synthesis pathway. Without functional tyrosinase, melanin cannot be produced, resulting in absence of pigment in skin, hair, and eyes. The other enzymes listed are involved in different metabolic pathways: homogentisic acid oxidase in tyrosine breakdown, phenylalanine hydroxylase in phenylalanine metabolism, and thiamine pyrophosphate is a coenzyme.

Marfan syndrome is an autosomal dominant connective tissue disorder affecting multiple systems including eyes (lens dislocation), cardiovascular system (aortic aneurysm, valve problems), and skeletal system (tall stature, scoliosis, hyperflexible joints). Since it affects all these systems, 'All of the above' is the correct answer.

Color blindness (specifically red-green color blindness) is a sex-linked trait carried on the X chromosome. Males (XY) are more frequently affected because they have only one X chromosome. Beri beri is a vitamin deficiency, tylosis is an autosomal dominant condition affecting esophagus skin, and albinism is an autosomal recessive trait - none of these are sex-linked.

Color blindness is a classic X-linked recessive trait - the gene is located on the X chromosome, making it sex-linked. Males (XY) express it with one affected X, while females (XX) need two affected X chromosomes. Baldness is sex-influenced (hormone-modified) rather than sex-linked. Diabetes is polygenic/multifactorial and polio is an infectious disease, neither being sex-linked genetic conditions.

A hypostatic gene is a gene whose phenotype is altered or suppressed.