Modes of Inheritance MCQs

During fertilization, the sperm penetrates the outer layer of the egg and fuses with the plasma membrane. Upon fusion, the sperm releases its contents inside the egg and the head and tail are degraded. Mitochondria are heavy in the tail so DNA does not get transferred from the sperm. Reference - Textbook of Langman's, 12th Edition, General Embryology Page number - 29

50% reduction in the normal gene product is associated with clinical signs and symptoms is a feature of autosomal dominant disorder. Reference: Robbins and Cotran Pathologic Basis of Diseases, 10 th ed Pg: 246

WHEN BOTH ALLELES EXPRESS THEMSELVES, ITS CALLED CO-DOMINANCE Reference: Robbins & Cotran Pathologic Basics of Diseases 9 th Edition page No.141

In some autosomal dominant disorders, like osteogenesis Imperfecta, phenotypically normal parents have more than one affected child. This is due to germline mosaicism. Reference: Robbins 9th/pg 160

Adult polycystic kidney disease is characterized by multiple expanding cysts affecting both kidneys that ultimately destroy the intervening parenchyma. In 85% to 90% of families, PKD1, on the short arm of chromosome 16, is the defective gene. This gene encodes a large (460-kDa) and complex cell membrane-associated protein called polycystin-1. Polycystic kidney disease in adults usually does not produce symptoms until the fourth decade of life, by which time the kidneys are quite large. The most common presenting complaint is flank pain or a heavy, dragging sensation. Acute distention of a cyst, either by intracystic hemorrhage or by obstruction, may cause excruciating pain. Sometimes attention is first drawn to the lesion on palpation of an abdominal mass. Intermittent gross hematuria commonly occurs. Reference :Robbins Basic Pathology, 10th edition, Page- 574

This child has features of Angelman syndrome, and the DNA analysis shows uniparental disomy. The Angelman gene encoded on chromosome 15 is subject to genomic imprinting. It is silenced on the paternal chromosome 15, but is active on the maternal chromosome 15. If the child lacks maternal chromosome 15, there is no active Angelman gene in the somatic cells. This gives rise to the abnormalities typical of this disorder. The same effect occurs when there is a deletion of the Angelman gene from the maternal chromosome 15. The other listed options do not occur in uniparental disomy. Reference: Robins Basic Pathology 10th ed/ pg 271

Inherited cancer syndrome: Familial retinoblastoma Familial adenomatous polyps of the colon Multiple endocrine neoplasia syndromes Neurofibromatosis types 1 and 2 Von Hippel- Lindau syndrome Familial cancers Breast cancer Ovarian cancer Colonic cancer other than familial adenomatous polyps Autosomal Recessive syndromes of Defective DNA Repair: Xeroderma pigmentosum Ataxia telangiectasia Bloom syndrome Fanconi anemia Reference: Robins basic pathology, 10th ed, Page: 201.