Assertion (A): DNA replication is semiconservative. Reason (R): Each new DNA molecule consists of one old and one new strand. MCQ with Answer and Explanation
Assertion (A): DNA replication is semiconservative.
Reason (R): Each new DNA molecule consists of one old and one new strand.
A. Both A and R are true, and R is the correct explanation.
B. A true, R false.
C. Both A and R are true, but R is not the correct explanation.
D. A false, R true.
Answer: Option A
Solution (By JKSSB Mock Tests)
Meselson and Stahl proved that after replication, each daughter DNA contains one parental and one newly synthesized strand. R exactly explains semiconservative.
Explanation:
O negative blood group lacks A and B antigens on RBCs and Rh antigen. Hence, it can be transfused to any person without causing agglutination, making it the universal donor. AB positive has both antigens and is the universal recipient. Blood grouping is based on ABO and Rh systems. O negative is crucial in emergency transfusions when blood type is unknown.
Explanation:
The four pulmonary veins drain oxygen-rich blood from the lungs into the left atrium. The pulmonary artery carries deoxygenated blood from right ventricle to lungs. Vena cava brings deoxygenated blood to right atrium.
Explanation:
Leptin is a peptide hormone produced primarily by adipocytes (fat cells). Its concentration in the blood is proportional to the amount of body fat. Leptin acts as a satiety signal, crossing the blood-brain barrier to act on receptors in the hypothalamus. It suppresses appetite (anorexigenic effect) and increases energy expenditure, thereby regulating long-term food intake and body weight. It is often called the 'satiety hormone' or 'fat hormone'.
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