Consider statements about genetics: 1. The human genome contains 23 pairs of chromosomes. 2. Sex is determined by the Y chromosome. 3. All mutations are harmful. Which are correct? MCQ with Answer and Explanation
Consider statements about genetics: 1. The human genome contains 23 pairs of chromosomes. 2. Sex is determined by the Y chromosome. 3. All mutations are harmful. Which are correct?
A. 1 and 3 only
B. 1 and 2 only
C. 2 and 3 only
D. 1, 2 and 3
Answer: Option B
Solution (By JKSSB Mock Tests)
Human somatic cells are diploid, containing 23 pairs of chromosomes (22 pairs of autosomes and 1 pair of sex chromosomes). The presence of the Y chromosome determines male sex (XY), while its absence results in female sex (XX). Mutations are random changes in DNA; while some are harmful, many are neutral, and some can be beneficial, providing the genetic variation necessary for evolution. Thus, statements 1 and 2 are correct.
Explanation:
Mitochondria and chloroplasts contain their own DNA and ribosomes (70S) and can replicate by binary fission, a feature supporting their endosymbiotic origin. Golgi apparatus, lysosomes, and rough ER cannot self-replicate; they are part of the endomembrane system and arise from pre-existing membranes. Mitochondria are thus semi-autonomous organelles.
Explanation:
Chaperone proteins like BiP assist in proper protein folding in the rough ER. Misfolded proteins are degraded. Golgi modifies, lysosome digests.
Explanation:
Chagas disease is caused by T. cruzi, transmitted by triatomine bugs. Sleeping sickness is T. brucei, malaria Plasmodium, leishmaniasis Leishmania.
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