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Genetic Disorders explores the medical conditions caused by one or more abnormalities in the genome, including inherited gene mutations and structural defects.
Phenylketonuria is an example of an inborn error of metabolism. This ‘error’ refers to:
Correct Answer:
(C) inherited lack of an enzyme
Phenylketonuria (PKU) is a disease caused by a metabolic disorder inherited as a recessive trait. The dominant gene ‘P’, in this case, codes for the enzyme, phenylalanine hydroxylase, formed in the liver cells. This enzyme catalyzes conversion of phenylalanine to tyrosine. In homozygous recessive genotypes, the absence of this enzyme causes a high level of phenylalanine in blood and tissues fluids. The phenotypic effects include a progressive mental retardation starting a few month after birth, seizures, and anomalies of teeth enamel and bones.
Ques: 2
The famous ‘Bubble Baby Disease’ is so called because:
Correct Answer:
(C) The suffering baby is treated in a germ-free plastic bubble
Bubble Baby Disease (severe combined immunodeficiency: SCID) is a rare genetic disorder characterized by the disturbed development of functional T cells and B cells caused by numerous genetic mutations. There are several forms of SCID. The famous ‘Bubble Baby Disease’ is named so as the suffering baby is treated in a germ-free plastic bubble.
Ques: 3
Haemophilia is a genetic disease carried by -
Correct Answer:
(B) Women, appear in men
Haemophilia is a genetic sex-linked disease in which blood clotting takes a long time in a patient (up to 24 hours) due to lack of thromboplastin protein in blood plasma. Women carry it while it appears in men (because men have one X chromosome but women have two). It is also called bleeder’s disease which was first found in Queen Victoria. So, it is also known as royal haemophilia.
Ques: 4
Which of the following is not a genetic disorder?
Correct Answer:
(C) Irritable Bowel Syndrome (IBS)
Down syndrome, haemophilia and sickle cell anaemia are hereditary diseases. Irritable Bowel Syndrome (IBS) is not a genetic disorder, it is a common gut disorder. The cause is not well known. Symptoms can be quite variable and include tummy (abdominal) pain, bloating and sometimes bouts of diarrhoea and/or constipation.
Note: Down Syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of the third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual disability, and characteristic facial features. It is also known as Mongolian idiocy.
Ques: 5
Down syndrome is a genetic disorder, which is caused due to -
Correct Answer:
(A) Due to changes in the number of the chromosomes
Down syndrome is a genetic disorder which is caused due to changes in the number of the chromosomes. In this, 21st pair of the chromosome are 3, instead of 2. So, the chromosome group is [2x + 1(chromosome number 21) = 47]. This syndrome is also known as Mongolian idiocy.
Ques: 6
Which one of the following is caused by the expression of a recessive gene present on sex chromosome?
Correct Answer:
(C) Muscular dystrophy
Muscular dystrophy is a hereditary disease linked with X-chromosome which is derived by the execution of the ineffective genes present on X-chromosome. This moves from generation to generation.
Ques: 7
Match List-I (Disease) with List-II (Types of disease) and select the correct answer using the codes given below:
List-I List-II
Haemophilia 1. Deficiency disease
Diabetes 2. Genetic disease
Correct Answer:
(B) Ringworm 4. Fungal infection
The correctly matched lists are as follows:
Haemophilia - Genetic disease
Diabetes - Hormonal disorder
Rickets - Deficiency disease
Ringworm - Fungal infection
Ques: 8
Which one of the following sets is correctly matched?
Correct Answer:
(C) Colour blindness, cell anaemia - Hereditary Haemophilia and Sickle
Diphtheria, pneumonia and leprosy are bacterial diseases. AIDS is a viral disease while syphilis and gonorrhoea are bacterial diseases. Colour blindness, haemophilia and sickle cell anaemia are hereditary diseases. Polio and Japanese B encephalitis are viral diseases, while plague is a bacterial disease.
Ques: 9
In respect of women, men can suffer more of colour blindness because-
Correct Answer:
(C) They have only one X-chromosome
Colour blindness is inherited in an X-linked recessive pattern. The genes are located on the X-chromosome which is one of the two sex chromosomes. In males (who have only one X-chromosome) one genetic change in each cell is sufficient to cause the condition. Males are affected by X-linked recessive disorders much more frequently than females (who have two X-chromosomes) in which a genetic change would have to occur on both copies of the chromosome to cause the disorder. A characteristic of X-linked inheritance is that father cannot pass X-linked traits to their sons.
Note: Lack of vitamin A causes night blindness not colour blindness. Colour blindness is a genetic disease which is inherited in an X-linked recessive pattern. Hence, option (c) is not correctly matched.