Biology

Human Genetics and Disorders

882 Questions

Human Genetics and Disorders covers the inheritance patterns, genetic mutations, and molecular basis of hereditary diseases. Topics include sex-linked traits, cancer genetics, and metabolic disorders. This section tests knowledge critical for biology exams and general science papers.

Genetic mutationsInherited disordersCancer geneticsGenetic testingMendelian inheritance

Human Genetics and Disorders Questions

Multiple choice

The signal termination of the signal transduction by the 7TM receptor becomes impossible if

  1. intrinsic GTPase activity of the G-protein becomes defective

  2. adnylate cyclase fails to bind to the G-alpha stimulatory subunit of G-protein

  3. the concentration of GTP is more in the cytosol

  4. G-alpha fails to reassociate with the G-beta, Gama subunits

  5. both Beta-adrenergic receptor kinase and Beta arrestin becomes defective
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The important step in the termination process is the resetting of the hormone-bound activated receptor. This is achieved by two processes. The first step marks the removal of hormone, and the receptor goes back to the inactivated state. The next step involves the phosphorylation of the serine and threonine residues in the carboxyl-terminal of the hormone-receptor complex by the receptor kinases. The final step includes the binding of B-arrestin to the phosphorylated receptor. This finally reduces the G-protein-activating ability of the receptor completely. Thus, the continuous activation of the G-protein is prevented by the phosphorylation and binding of B-arrestin that desensitize the receptor after continuous exposure to epinephrine hormone. This marks the termination of the cascade. However, if beta-adrenergic receptor kinase and Beta arrestin becomes defective, the signal termination of the signal transduction by the 7TM receptor becomes impossible.

Multiple choice

Obesity is considered to be the result of the combination of deletions, SNPs and gene mutations. Which among the following does not characterise monogenic obesity?

  1. It occurs due to the congenital leptin deficiency.

  2. The common monogenic obesity disorder was represented by excess of MC4R.

  3. The phenotype is directly and strongly related to the genotype.

  4. In leptin melanocortin pathway, leptin crosses the blood brain barrier and triggers the neurons present in the hypothalamus to generate peptides.

  5. The receptor gene mutations might be one of the reasons for severe obesity.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The mutation in the melanocortin-4 receptor protein (MC4R) which is a component of leptin-melanocortin pathway was detected to be related to obesity. The common monogenic obesity disorder was represented by MC4R deficiency. The obesity was accounted due to homozygous and heterozygous mutations in MC4R.

Multiple choice

The genetic abnormality called mongolism is an example of

  1. Allosomal abnormality

  2. Autosomal abnormality

  3. Y chromosomal abnormality

  4. X chromosomal abnormality

  5. Sex chromosomal abnormality
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The genetic abnormality called mongolism is an example of autosomal abnormality.

Multiple choice

Certain traits such as baldness in human beings, which are actually determined by autosomal genes but their expression is influenced by sex hormones are called

  1. sex limited traits

  2. sex linked traits

  3. sex influenced traits

  4. sexual traits

  5. homozygous traits
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Certain traits such as baldness in human biings, which are actually determined autosomal genes but their expression being influenced by sex hormones are called sex influenced traits.

Multiple choice

Assertion (A): Cri-du-chat syndrome is an intrachromosomal aberration. Reason (R): It is caused in humans by deletion of a part of short arm of chromosome 5.

In the following question there are two statements, Assertion (A) and Reason (R), consider both the statements independently and mark your answers as under:
1. If A and R both are correct and R is correct explanation of A.
2. If A and R both are correct and R is not correct explanation of A.
3. If A is correct and R is incorrect.
4. If A is incorrect and R is correct.
5. If A and R both are incorrect.

  1. 1

  2. 2

  3. 3

  4. 4

  5. 5
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Both Assertion (A) and Reason (R) statements are correct, and R is correct explanation of A. In chromosomal aberration there is an alteration in the structural organisation of chromosome.  Aberrations are of two types, Intrachromosomal aberration :  when the alteration is within single chromosome. Interchromosomal aberration : when alteration involves the intervention of two or more chromosomes. Cri-du-chat syndrome in humans is caused by deletion of a part of short arm of chromosome 5. It involves alteration in only one chromosome; hence it is an intrachromosomal aberration.

Multiple choice

Which of the following are examples of autosomal recessive hereditary disorders?

  1. Albinism
  2. Phenylketonuria
  3. Achondroplasia
  4. Brachydatyly

  1. 1 and 2

  2. 1 and 3

  3. 2 and 3

  4. 2 and 4

  5. 3 and 4
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Albinism and Phenylketonuria are examples of autosomal recessive hereditary disorders. Albinism is caused due to inability to produce melanin pigment characterized by absence of normal colouration of skin. Phenylketonuria is a metabolic disorder which arises due to deficiency of an enzyme phenylalanine hydroxylase,  which converts phenylalanine to tyrosine.

Multiple choice

Which of the following cartilagenous disorders causes dwarfism?

  1. Osteoarthritis

  2. Achondroplasia

  3. Costochondritis

  4. Relapsing polychondritis

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Achondroplasia occurs as a sporadic mutation in approximately 85% of cases (associated with advanced paternal age) or may be inherited in an autosomal dominant genetic disorder that is a common cause of dwarfism.

Multiple choice

In humans, certain specific diseases are caused by point mutations. Which among the following diseases is associated with HEXA gene being present on chromosome 15?

  1. Color blindness

  2. Tay–Sachs disease

  3. Sickle-cell anemia

  4. Neurofibromatosis

  5. Cystic fibrosis
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The cause of Tay–Sachs disease is a genetic defect that is passed from parent to child. This genetic defect is located in the HEXA gene, which is found on chromosome 15. The HEXA gene makes part of an enzyme called beta-hexosaminidase A, which plays a critical role in the nervous system.

Multiple choice

Which of the following mutations are not the point mutations?

  1. Silent mutations

  2. Missense mutation

  3. Loss-of-function mutations

  4. Nonsense mutation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Loss-of-function mutations are the result of gene product having less or no function. When the allele has a complete loss of function (null allele) it is often called an amorphic mutation. Phenotypes associated with such mutations are most often recessive. It is not a point mutation.

Multiple choice

The mutations causing no change in their products are known as

  1. missense mutations

  2. nonsense mutations

  3. silent mutations

  4. splice-site mutations
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Most amino acids are encoded by several different codons. For example, if the third base in the TCT codon for serine is changed to any one of the other three bases, serine will still be encoded. Such mutations are said to be silent because they cause no change in their product and cannot be detected without sequencing the gene (or its mRNA).

Multiple choice

Which among the following is an autosomal recessive metabolic genetic disorder?

  1. Sickle-cell disease

  2. Cystic fibrosis

  3. Tay-Sachs disease

  4. Phenylketonuria
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder characterized by an error in the genetic code for the hepatic enzyme phenylalanine hydroxylase (PAH), rendering it nonfunctional.This enzyme is necessary to metabolize the amino acid phenylalanine (Phe) to the amino acid tyrosine.