In a plant cell, which one of the following contains their own DNA ?
- A.Nucleus and Endoplasmic Reticulum
- B.Ribosome and Golgi apparatus
- C.Mitochondria and Chloroplast
- D.Chloroplast and Vacuoles
Correct answer
Explanation
The correct answer is C, mitochondria and chloroplast. Besides the nucleus, these are the only organelles of a plant cell that carry their own DNA.
Mitochondria and chloroplasts have small circular DNA molecules and their own 70S ribosomes, so they can make some of their own proteins and divide on their own. That is why they are called semi-autonomous organelles. The endosymbiotic theory explains this: they are thought to descend from bacteria that were engulfed by an ancestral cell, mitochondria from aerobic bacteria and chloroplasts from cyanobacteria. Mitochondria release energy in respiration, and chloroplasts carry out photosynthesis.
A is wrong because the endoplasmic reticulum has no DNA of its own, even though the nucleus does.
B is wrong because ribosomes are made of RNA and protein, and the Golgi apparatus has no DNA.
D is wrong because vacuoles are sacs of cell sap and have no DNA.
Exam tip: semi-autonomous organelles with their own DNA and 70S ribosomes are mitochondria and chloroplasts.
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.
Show answer
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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