Which of the following groups of diseases consists of genetic diseases?
- A.Sickle cell anaemia, AIDS, Down syndrome
- B.AIDS, Hepatitis B, Cancer
- C.Haemophilia, Hepatitis B, Colour blindness
- D.Sickle cell anaemia, Haemophilia, Down syndrome
Correct answer
Explanation
The correct answer is D, Sickle cell anaemia, Haemophilia, Down syndrome. All three are genetic disorders, caused by changes in genes or chromosomes and passed on through birth, not by germs. Sickle cell anaemia is an autosomal recessive disease in which a single change in the haemoglobin gene makes red blood cells sickle-shaped. Haemophilia is a sex-linked recessive disorder carried on the X chromosome, in which blood does not clot properly; it mostly affects males, and it is called the royal disease because it spread among Queen Victoria's descendants. Down syndrome is a chromosomal disorder caused by an extra copy of chromosome 21, also called trisomy 21. Option A is wrong because AIDS is caused by the HIV virus and is not inherited through genes. Option B is wrong because AIDS and Hepatitis B are viral infections, and most cancers come from mutations acquired during life. Option C is wrong because Hepatitis B is a viral infection, even though haemophilia and colour blindness are genetic. Exam tip: genetic disorders include sickle cell anaemia, haemophilia, colour blindness, thalassaemia and Down syndrome.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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