Genetic Disorders is part of Biology. Below are notes on 7 sub-topics, followed by practice MCQs from State PSC and UPSC papers.

Causes of Genetic Disorders: Gene Mutations and Chromosomal Aberrations

  • Genetic disorders result from genetic defects, categorized as Gene Mutations or Chromosomal Aberrations.
  • Gene Mutations: Alterations in the nucleotide sequence within a gene.
  • Albinism: An autosomal recessive genetic disorder caused by mutations (e.g., in TYR gene) leading to the deficiency of the enzyme tyrosinase, which is crucial for melanin synthesis.
  • Mutagens: Agents that induce permanent changes (mutations) in DNA.
  • Categories of Mutagens:
    • Physical Mutagens:
      • Ionizing Radiation: X-rays, gamma rays, and radioactive isotopes (e.g., Carbon-14). Directly cause DNA strand breaks and base damage.
      • Professionals at risk: X-ray technicians, researchers handling radioactive isotopes like Carbon-14.
    • Chemical Mutagens:
      • Alkylating Agents: Chemically add alkyl groups to DNA bases, altering their pairing properties (e.g., EMS - Ethyl methanesulfonate, MMS - Methyl methanesulfonate, EES - Ethyl ethanesulfonate).
      • Base Modifiers: Chemically alter existing DNA bases. Hydroxylamine (HA) is a base modifier that modifies cytosine and is not an alkylating agent.
      • Other types: Base analogs (mimic DNA bases), Intercalating agents (insert into DNA).
      • Professionals at risk: Dyers and Painters due to exposure to various mutagenic chemicals in their materials.
  • Chromosomal Aberrations: Changes in chromosome structure (e.g., deletions, duplications, translocations, inversions) or number (e.g., aneuploidy like trisomy).

Chromosomal Disorders: Numerical and Structural Aberrations

  • Chromosomal disorders result from numerical or structural changes in chromosomes.
  • Numerical Aberrations (Aneuploidy): Involve the gain or loss of one or more whole chromosomes.
  • Trisomy: Presence of an extra copy of a chromosome (e.g., 2n+1).
  • Monosomy: Absence of one chromosome (e.g., 2n-1).
  • Down Syndrome (Trisomy 21): Caused by the presence of an additional copy of chromosome number 21. Also known as Mongolism.
  • Klinefelter Syndrome (47, XXY): A numerical abnormality of sex chromosomes, caused by an extra X chromosome in males. Individuals possess one Barr body.
  • Turner Syndrome (45, XO): A numerical abnormality of sex chromosomes, caused by the absence of one X chromosome in females. Individuals do not possess a Barr body.
  • Barr Body: An inactivated X chromosome found in somatic cells of individuals with two or more X chromosomes. The number of Barr bodies is N-1, where N is the total number of X chromosomes.

Complex (Multifactorial) Disorders: Genetic Component

  • Complex (Multifactorial) Disorders: Result from interaction between multiple genetic predispositions and environmental factors.
  • Examples: Heart disease, diabetes, certain cancers, neural tube defects (NTDs).
  • Spina Bifida: A common neural tube defect, categorized as a complex disorder.
  • Spina Bifida Characteristic: Incomplete closing of the backbone (vertebrae) and the membranes (meninges) surrounding the spinal cord.
  • Contributing Factors (Spina Bifida): Genetic susceptibility combined with environmental factors, notably maternal folic acid deficiency during early pregnancy.

Definition and Classification of Genetic Disorders

  • Genetic disorders: Diseases caused by abnormalities in an individual's DNA (genome).
  • Genetic disorders can be inherited from parents or arise from new mutations.
  • Genetic disorders are non-communicable diseases.
  • Classification of Genetic Disorders:
    • Mendelian Disorders (Single-gene disorders): Caused by a mutation in a single gene.
      • Examples: Sickle Cell Anemia (autosomal recessive), Hemophilia (X-linked recessive), Colour Blindness (X-linked recessive), Albinism (autosomal recessive).
    • Chromosomal Disorders: Caused by a change in the number or structure of chromosomes.
      • Example: Down Syndrome (Trisomy 21).
    • Multifactorial Disorders: Caused by a combination of genetic and environmental factors (not explicitly detailed in MCQs but good for completeness).
  • Progeria: A rare genetic disorder characterized by dramatic, premature aging in childhood.
  • Diseases that are NOT genetic disorders (from MCQs):
    • AIDS: Caused by HIV (virus).
    • Hepatitis B: Caused by Hepatitis B virus.
    • Cancer: Often multifactorial, involving somatic mutations, but not typically classified as a single inherited genetic disorder like Mendelian or chromosomal diseases.
    • Night blindness: Most commonly caused by Vitamin A deficiency, not primarily a genetic disorder.

Diagnosis of Genetic Disorders: Pedigree Analysis, Karyotyping, Molecular Techniques (PCR, DNA sequencing)

  • Diagnosis of Genetic Disorders: Identification of genetic mutations, chromosomal aberrations, or abnormal protein products linked to inherited conditions.
  • Pedigree Analysis:
    • Graphical representation of genetic traits across generations within a family.
    • Helps determine inheritance patterns: autosomal dominant, autosomal recessive, X-linked, mitochondrial.
    • Uses standardized symbols (e.g., square for male, circle for female, shaded for affected, half-shaded for carrier).
    • Estimates recurrence risk for genetic diseases in future offspring.
  • Karyotyping:
    • Ordered arrangement of an individual's chromosomes from a cell (typically metaphase stage lymphocytes).
    • Used to detect numerical chromosomal abnormalities (aneuploidy):
      • Trisomy (e.g., Down syndrome Trisomy 21, Klinefelter syndrome - XXY).
      • Monosomy (e.g., Turner syndrome - XO).
    • Also identifies large structural chromosomal abnormalities (e.g., deletions, duplications, translocations, inversions).
  • Molecular Techniques:
    • PCR (Polymerase Chain Reaction):
      • In vitro method to amplify specific DNA segments exponentially.
      • Used for detecting specific gene mutations, pathogen identification, and as a preparatory step for DNA sequencing or fingerprinting.
    • DNA Sequencing:
      • Determines the precise order of nucleotides (A, T, C, G) in a DNA molecule.
      • Identifies point mutations, small insertions, or deletions responsible for genetic disorders.
      • Methods include Sanger sequencing and Next-Generation Sequencing (NGS).
    • DNA Fingerprinting:
      • Analyzes unique patterns of variable number tandem repeats (VNTRs) or short tandem repeats (STRs) in an individual's DNA.
      • Applications include:
      • Forensic investigations (matching DNA samples from crime scenes).
      • Paternity and maternity testing (establishing biological parentage).
      • Study of inherited diseases (by identifying linked markers or specific gene variants).
      • Biodiversity studies and evolutionary biology.

Mendelian Disorders: Autosomal Dominant, Autosomal Recessive, X-linked

  • Mendelian Disorders: Single-gene disorders, following Mendelian inheritance patterns.
  • Autosomal Dominant Disorders:
    • Myotonic Muscular Dystrophy: Also known as Steinert's Disease.
  • Autosomal Recessive Disorders:
    • Thalassemia:
      • Hereditary blood disease.
      • Characterized by reduced synthesis of either $\alpha$-globin or $\beta$-globin chains of hemoglobin.
      • Affects blood, leading to anemia.
    • Phenylketonuria (PKU):
      • Inherited metabolic disorder.
      • Caused by a defect in the gene encoding phenylalanine hydroxylase, leading to phenylalanine accumulation.
  • X-linked Recessive Disorders:
    • Haemophilia:
      • Genetic, heritable disease.
      • Leads to non-clotting of blood due to deficiency of specific clotting factors.
      • Known as "Royal Disease."
      • X-linked recessive; males are more commonly affected, females are typically carriers.
      • Haemophilia is low in women because it is X-linked recessive.
    • Colour Blindness:
      • Genetic, heritable disease.
      • X-chromosome linked recessive.
      • Primarily affects the ability to distinguish between red light and green light.
      • Males are more commonly affected.
      • Caused by recessive genes present on the X chromosome.
  • General Points:
    • Thalassemia is an autosomal disease. Haemophilia and Colour blindness are X-linked diseases.
    • Genetic diseases like Haemophilia, Colour blindness, Thalassemia, and Phenylketonuria are heritable/inherited disorders caused by gene defects.
    • The sex of a newborn is determined by the chromosomes inherited from the father (X or Y).

Mitochondrial Inheritance and Disorders

  • Mitochondrial DNA (mtDNA) is circular, double-stranded, located in mitochondria, separate from nuclear DNA.
  • Mitochondrial inheritance is strictly maternal; offspring inherit mtDNA exclusively from the mother.
  • Sperm mitochondria typically do not contribute to the zygote's cytoplasm, preventing paternal mtDNA transmission.
  • Mitochondrial disorders result from mutations in mtDNA.
  • Mitochondrial Replacement Therapy (MRT) is a technique used to prevent the transmission of mitochondrial diseases from an affected mother to her child.
  • MRT techniques can involve:
    • Maternal Spindle Transfer (MST): Transferring the nucleus from the mother's egg (containing faulty mitochondria) into an enucleated donor egg (with healthy mitochondria) before in vitro fertilization.
    • Pronuclear Transfer (PNT): Transferring the pronuclei from a fertilized egg (containing faulty mitochondria) into an enucleated, fertilized donor egg (with healthy mitochondria) after in vitro fertilization.
  • MRT results in a child with nuclear DNA from both biological parents and mitochondrial DNA from a healthy donor.

29. Deficiency, Non-Contagious and

Other Diseases

Practice MCQs: Genetic Disorders

Causes of Genetic Disorders: Gene Mutations and Chromosomal Aberrations

  1. Albinism is caused due to the deficiency of a/ an:

    Asked in: OPSC CS Prelims 2020

    1. Hormone
    2. Enzyme
    3. Vitamin
    4. Metal
    Show answer

    Answer: B. Enzyme

    Albinism is a group of inherited disorders characterized by a deficiency or absence of pigment (melanin) in the skin, hair, and eyes. This lack of melanin production is typically caused by mutations in genes that code for enzymes involved in the metabolic pathway that produces melanin, such as tyrosinase.

  2. Which of the following professional (s) are more likely to run the risk of a permanent change in their cell’s DNA? I. Researchers using carbon-14 isotope II. X-ray technician III. Coal miner IV. Dyer and Painter Select the correct answer by using the codes given below:

    Asked in: UPPCS Prelims 1996

    1. II alone
    2. I, II and III
    3. I, II and IV
    4. I, III and IV
    Show answer

    Answer: C. I, II and IV

    The life cycle of the malarial parasite in humans has distinct stages, and the initial site of multiplication after transmission is the liver. Exposure to radiation (ionizing radiation like X- rays and radioactive isotopes) and certain industrial chemicals are major causes of DNA mutations.

  3. Mutagen that is not alkylating agent is

    Asked in: Agri. Officer 2020

    1. EMS
    2. MMS
    3. EES
    4. HA
    Show answer

    Answer: D. HA

    Alkylating agents are mutagens that covalently add alkyl groups to DNA bases. EMS, MMS, and EES are well-known examples that specifically alkylate guanine and other bases. Hydrazine, while mutagenic, operates through different chemical interactions with DNA.

Chromosomal Disorders: Numerical and Structural Aberrations

  1. Which one of the following examples of genetic-disorder or disease is due to the numerical abnormalities in the sex chromosome ?

    Asked in: UPSC Geoscientist 2024

    1. Turner's syndrome
    2. Down's syndrome
    3. Haemophilia
    4. Alkaptonuria
    Show answer

    Answer: A. Turner's syndrome

    Turner's syndrome is a genetic disorder affecting females, caused by the complete or partial absence of one X chromosome (monosomy X, 45,XO). This is a numerical abnormality involving the sex chromosome.

  2. In humans trisomy of chromosome number 21 is responsible for

    Asked in: RPSC RAS Prelims 2018

    1. Haemophilia
    2. Klinefelter Syndrome
    3. Down Syndrome
    4. Turner Syndrome
    Show answer

    Answer: C. Down Syndrome

    Down Syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. This condition is known as Trisomy 21.

  3. Trisomy 21 is known as -

    Asked in: RPSC RAS Prelims 2021

    1. Evans syndrome
    2. Edwards syndrome
    3. Down syndrome
    4. Gray baby syndrome
    Show answer

    Answer: C. Down syndrome

    Trisomy 21 is the medical term for a genetic disorder caused by the presence of an extra copy of chromosome 21. This condition is commonly known as Down syndrome.

  4. Barr body is absent in somatic cell of

    Asked in: WBPSC CS Prelims 2017

    1. Klinefelter syndrome individual
    2. Tripple X syndrome individual
    3. Turner syndrome individual
    4. Sub-human mammalian female individual
    Show answer

    Answer: C. Turner syndrome individual

    A Barr body is an inactivated X chromosome found in the somatic cells of most female mammals. It is a mechanism of dosage compensation to equalize the expression of X-linked genes between males (XY) and females (XX). The number of Barr bodies in a cell is typically one less than the total number of X chromosomes (N-1 rule). - Klinefelter syndrome (XXY): Individuals have 2 X chromosomes (N=2). Number of Barr bodies = 2 - 1 = 1. - Triple X syndrome (XXX): Individuals have 3 X chromosomes (N=3). Number of Barr bodies = 3 - 1 = 2. - Turner syndrome (XO): Individuals have only 1 X chromosome (N=1). Number of Barr bodies = 1 - 1 = 0. Thus, Barr bodies are absent. - Sub-human mammalian female individual (typically XX): Females have 2 X chromosomes (N=2). Number of Barr bodies = 2 - 1 = 1. Therefore, Barr bodies are absent in individuals with Turner syndrome.

  5. In human beings, disorder caused due to trisomy of 21st chromosome is:

    Asked in: MPPSC CS Prelims 2024

    1. Turner Syndrome
    2. Down Syndrome
    3. Super Female Syndrome
    4. Klinefelter Syndrome
    Show answer

    Answer: B. Down Syndrome

    Trisomy 21 specifically refers to having three copies of chromosome 21, which is the underlying cause of Down Syndrome.

  6. Cause of 'Down's syndrome' in humans is

    Asked in: Junior Accountant and TRA 2013

    1. presence of an additional copy of the chromosome number '21'
    2. absence of chromosome number '21'
    3. presence of an additional copy of the 'X' chro‐ mosome
    4. absence of 'X' chromosome
    Show answer

    Answer: A. presence of an additional copy of the chromosome number '21'

    Down's syndrome is a chromosomal disorder resulting from an extra copy of chromosome 21.

  7. Down syndrome is also known as

    Asked in: Civil Engg GA 24 2023 CO 1505 2024

    1. Edwards' syndrome
    2. Patau syndrome
    3. Mongolism
    4. None of the above
    Show answer

    Answer: C. Mongolism

    Down syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. The term 'Mongolism' was historically used to describe individuals with Down syndrome due to perceived facial similarities to people of East Asian descent. However, this term is considered outdated, inaccurate, and stigmatizing by medical professionals and advocacy groups.

Complex (Multifactorial) Disorders: Genetic Component

  1. Ques #: 97 the birth defect where there is incomplete closing of the back bone and membrane around spinal chord is known as

    Asked in: Sr. Teacher Gr II (Spl. Edu.) 2015

    1. spina bifida
    2. spinal chord injury
    3. muscular dystrophy
    4. multiple sclerosis
    Show answer

    Answer: A. spina bifida

    Spina bifida is a congenital condition that affects the development of the spinal cord and spine. It occurs when the neural tube fails to close properly during pregnancy.

Definition and Classification of Genetic Disorders

  1. Which of the following groups of diseases includes genetic diseases?

    Asked in: HAS Prelims 2021

    1. Sickle Cell Anemia, AIDS, Down Syndrome
    2. AIDS, Hepatitis B, Cancer
    3. Hemophilia, Hepatitis B, Color Blindness
    4. Sickle Cell Anemia, Hemophilia, Down Syn‐ drome
    Show answer

    Answer: D. Sickle Cell Anemia, Hemophilia, Down Syn‐ drome

    - Sickle Cell Anemia is a hereditary blood disorder caused by a mutation in the gene encoding hemoglobin. It is a genetic disease. - Hemophilia is a hereditary bleeding disorder caused by defects in genes for blood clotting factors. It is a genetic disease, often X-linked. - Down Syndrome is a chromosomal disorder caused by an extra copy of chromosome 21 (trisomy 21). It is a genetic disease. - AIDS (Acquired Immunodeficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV). It is an infectious disease, not genetic. - Hepatitis B is caused by the Hepatitis B Virus (HBV). It is an infectious disease, not genetic. - Cancer can be caused by genetic mutations (inherited or acquired), but it is a complex disease resulting from uncontrolled cell growth, not solely determined by inherited genes in most cases, although genetic predisposition plays a role. In the context of distinguishing purely genetic/hereditary diseases from infectious ones, it's often categorized differently.

  2. Which of the following group of diseases comprises genetic diseases?

    Asked in: HAS Prelims 2021

    1. Sickle cell anemia, AIDS, Down syndrome
    2. AIDS, Hepatitis B, Cancer
    3. Hemophilia, Hepatitis B, Colour blindness
    4. Sickle cell anemia, Hemophilia, Down syn‐ drome
    Show answer

    Answer: D. Sickle cell anemia, Hemophilia, Down syn‐ drome

    - Genetic diseases are passed down through families or occur due to new mutations in DNA. - AIDS is caused by the Human Immunodeficiency Virus (HIV). - Hepatitis B is caused by the Hepatitis B Virus (HBV). - Cancer is a complex disease often involving both genetic mutations (inherited or acquired) and environmental factors, but not all cancers are strictly classified as monogenic or chromosomal genetic disorders in the context of typical genetic disease lists like this.

  3. Genetic disorders are :

    Asked in: OPSC CS Prelims 2018

    1. Communicable diseases
    2. Non-communicable diseases
    3. Life-style diseases
    4. Toxicity diseases
    Show answer

    Answer: B. Non-communicable diseases

    Genetic disorders are not spread between individuals, classifying them as non-communicable diseases.

  4. Paa is a 2009 Indian comedy-drama film directed by R. Balakrishnan in which Amitabh Bachchan is shown to suffer with a rare genetic disease of childhood characterized by dramatic, premature ageing. What is this type of disorder called ?

    Asked in: PPSC CS Prelims 2013

    1. Conn's syndrome
    2. Acromegaly
    3. Progeria
    4. Down's syndrome
    Show answer

    Answer: C. Progeria

    The film "Paa" features a character with Hutchinson–Gilford progeria syndrome (HGPS), commonly known as Progeria. This is an extremely rare genetic disorder causing affected children to age rapidly from early childhood. Symptoms include growth failure, hair loss, aged-looking skin, joint abnormalities, and cardiovascular problems, leading to a significantly reduced lifespan. Conn's syndrome involves excess aldosterone. Acromegaly involves excess growth hormone in adulthood. Down's syndrome is a chromosomal disorder causing intellectual disability and characteristic physical features. None of these describe the premature aging shown in the film.

  5. Which one of the following is not a genetic disease?

    Asked in: UPPCS Prelims 2017

    1. Night blindness
    2. Albinism
    3. Haemophilia
    4. Colour blindness
    Show answer

    Answer: A. Night blindness

    Night blindness can be caused by nutritional deficiencies (Vitamin A) or genetic disorders.

Diagnosis of Genetic Disorders: Pedigree Analysis, Karyotyping, Molecular Techniques (PCR, DNA sequencing)

  1. Which of the following is/are correct regarding DNA fingerprinting?

    Asked in: Assistant Auditor (Direct) 2021

    1. It helps in the study of inherited diseases
    2. It helps in the forensic investigations
    3. It helps in the detection of biological parents
    4. All of the above
    Show answer

    Answer: D. All of the above

    DNA fingerprinting, also known as DNA profiling, is a technique used to identify individuals based on their unique patterns of DNA. Its applications are vast and include: Forensics: Identifying criminals from crime scene evidence. Paternity Testing: Establishing biological relationships. Medical Diagnostics: Identifying genetic disorders and inherited diseases. Anthropology and Archaeology: Studying evolutionary relationships and identifying ancient remains.

Mendelian Disorders: Autosomal Dominant, Autosomal Recessive, X-linked

  1. Which of the following is known as Royal Disease ?

    Asked in: GPSC Prelims CSP 2 2017

    1. Sickle Cell anaemia
    2. Alzheimer's disease
    3. Haemophilia
    4. Colour blindness
    Show answer

    Answer: C. Haemophilia

    Haemophilia is known as the "Royal Disease" because it affected the royal families of Europe, most notably the descendants of Queen Victoria of the United Kingdom. She was a carrier of the mutation, and the condition spread through her offspring to the royal families of Spain, Germany, and Russia.

  2. Which of the following statements is/are correct ? 1. Haemophilia is a genetic disorder which leads to decrease in the white blood cells 2. The sex of new born baby is determined by the chromosomes inherited from the mother 3. Haemophilia is low in women due to a dominant gene found on Y chromosome

    Asked in: GPSC Prelims CSP 2 2019

    1. 1, 2 and 3
    2. 3 only
    3. 1 and 3 only
    4. 1 and 2 only
    Show answer

    Answer: D. 1 and 2 only

    - Statement 1: Haemophilia is a genetic disorder which leads to decrease in the white blood cells. This is incorrect. Haemophilia is a bleeding disorder caused by a deficiency in blood clotting factors, not affecting white blood cells. - Statement 2: The sex of new born baby is determined by the chromosomes inherited from the mother. This is incorrect. The mother contributes an X chromosome. The father contributes either an X or a Y chromosome via the sperm, thus determining the sex (XX for female, XY for male). - Statement 3: Haemophilia is low in women due to a dominant gene found on Y chromosome. This is incorrect. Haemophilia is an X-linked recessive disorder. It is less common in women than men because women have two X chromosomes (requiring both to be affected for the disorder, or one affected and skewed inactivation), while men have only one X (so one affected X results in the disorder). The Y chromosome is not involved, and the gene is recessive, not dominant.

  3. What happens in human Thalassemias? reduce $\alpha$ - globin synthesis reduce $\beta$ - globin synthesis enhance $\alpha$ and $\beta$ - globin synthesis

    Asked in: TNPSC CS Prelims 2019

    1. 1 alone correct
    2. 2 alone correct
    3. 1 and 2 are correct
    4. 3 alone correct
    Show answer

    Answer: C. 1 and 2 are correct

    Thalassemias result from genetic defects that impair the synthesis of either the alpha or beta globin chains of hemoglobin.

  4. Thalassemia is a hereditary disease which affects

    Asked in: UKPSC CS Prelims 2016

    1. Blood
    2. Lungs
    3. Heart
    4. Kidney
    Show answer

    Answer: A. Blood

    Thalassemia is a group of inherited genetic disorders that affect the production of hemoglobin, the protein in red blood cells responsible for carrying oxygen. Defective hemoglobin production leads to anemia and various complications affecting red blood cells and related organs.

  5. The X-chromosome linked colour blindness affects the ability to detect the difference between which of the following lights ?

    Asked in: UPSC CISF AC EXE 2018

    1. Green light and red light
    2. Yellow light and blue light
    3. Blue light and violet light
    4. Yellow light and red light
    Show answer

    Answer: A. Green light and red light

    X-linked colour blindness primarily impairs the ability to distinguish between red and green colours.

  6. Which of the following diseases is autosomal?

    Asked in: WBPSC CS Prelims 2023

    1. Haemophilia
    2. Thalassemia
    3. Colourblindness
    4. All of the above
    Show answer

    Answer: B. Thalassemia

    - Autosomal diseases are caused by mutations on non-sex chromosomes (autosomes). - Sex-linked diseases are caused by mutations on sex chromosomes (X or Y). - Haemophilia and Colourblindness are X-linked recessive disorders. - Thalassemia is an autosomal recessive disorder.

  7. The heritable disease is

    Asked in: UPPSC Upper Mains 2007

    1. Diphtheria
    2. Jaundice
    3. Hemophilia
    4. Whooping Cough
    Show answer

    Answer: C. Hemophilia

    Heritable diseases are caused by genetic mutations or abnormalities that are passed down from parents to their offspring. Hemophilia is a group of inherited bleeding disorders caused by a deficiency in certain blood clotting factors, resulting from mutations on genes located on the X chromosome.

  8. Haemophilia is a genetic disorder which leads to

    Asked in: UPPCS Prelims 1998

    1. decrease in haemoglobin level
    2. rheumatic heart disease
    3. decrease in WBC
    4. non-clotting of blood
    Show answer

    Answer: D. non-clotting of blood

    Haemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting or coagulation. This leads to prolonged bleeding after injury, surgery, or even minor cuts, and can also cause spontaneous internal bleeding, especially in joints and muscles. It is caused by a deficiency in specific blood clotting factors (Factor VIII in Haemophilia A, Factor IX in Haemophilia B).

  9. Which one of the following genetic diseases is sex-linked?

    Asked in: UPPCS Prelims 1999

    1. Royal haemophilia
    2. Tay Sachs disease
    3. Cystic fibrosis
    4. Hypertension
    Show answer

    Answer: A. Royal haemophilia

    Sex-linked genetic diseases are those caused by genes located on the sex chromosomes, most commonly the X chromosome. Haemophilia (both Type A and B, sometimes referred to as Royal Haemophilia due to its prevalence in European royal families) is a classic example of an X-linked recessive disorder.

  10. Which of the following is also known as Steinert's Disease ?

    Asked in: Asst. Statistical Officer 2

    1. Duchene Muscular Dystrophy
    2. Becker's Muscular Dystrophy
    3. Myotonic Muscular Dystrophy
    4. Limb Griddle Muscular Dystrophy
    Show answer

    Answer: C. Myotonic Muscular Dystrophy

    Steinert's Disease is a specific genetic disorder affecting muscles and other organs, characterized by myotonia (difficulty relaxing muscles) and progressive muscle weakness. It is a type of muscular dystrophy.

  11. Ǔनम्नͧलͨखत में से कौन सा आनुवंͧशक रोग है ?

    Asked in: JUNIOR ACCOUNTANT AND TRA 2013

    1. (1) रेबीज़
    2. (2) विणर्त अंधता
    3. (3) पोlलियो
    4. (4) चेचक
    Show answer

    Answer: B. (2) विणर्त अंधता

    Colour blindness is a hereditary (genetic) disease.

  12. Which of the following is a hereditary disease ?

    Asked in: JUNIOR ACCOUNTANT AND TRA 2013

    1. Rabies
    2. Colour blindness
    3. Polio
    4. Small-pox
    Show answer

    Answer: B. Colour blindness

    Colour blindness is a hereditary disease.

  13. Which one of the following diseases is caused due to defect in gene ?

    Asked in: Assistant Accountant 2012

    1. Haemophilia
    2. Typhoid
    3. Malaria
    4. Jaundice
    Show answer

    Answer: A. Haemophilia

    Genetic disorders are caused by abnormalities in an individual's genome, which can be due to mutations in a single gene or multiple genes. Haemophilia is a classic example of a sex-linked genetic disorder.

  14. Phenylketonuria is an example of A) sexual overstimulation B) bone malfunction C) infectious disease D) inherited disorder

    Asked in: ASSISTANT AUDIT OFFICER 2017 18 2017

    1. sexual overstimulation
    2. bone malfunction
    3. infectious disease
    4. inherited disorder
    Show answer

    Answer: D. inherited disorder

    Inherited disorders are conditions caused by abnormalities in an individual's genome. These abnormalities can be inherited from one or both parents.

Mitochondrial Inheritance and Disorders

  1. In the context of hereditary diseases, consider the following statements : Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of egg. A child inherits mitochondrial diseases entirely from mother and not from father. Which of the statements given above is/are correct?

    Asked in: UPSC IAS 2021

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Show answer

    Answer: C. Both 1 and 2

    - Statement 1: Mitochondrial Replacement Therapy (MRT), including Pronuclear Transfer or Maternal Spindle Transfer techniques, aims to prevent the transmission of mitochondrial diseases from mother to child. These procedures involve transferring the nucleus from the affected mother's egg (or zygote) into a donor egg (or zygote) that has had its nucleus removed but retains healthy mitochondria. This can be performed either before or after fertilization (in vitro fertilization). - Statement 2: Mitochondria, organelles responsible for energy production within cells, contain their own DNA (mtDNA). In humans, mtDNA is almost exclusively inherited from the mother because the egg contributes the vast majority of cytoplasm (containing mitochondria) to the zygote, while the sperm contributes primarily nuclear DNA. Therefore, mitochondrial diseases are maternally inherited.