Consider statements about human respiration: 1. Hemoglobin has a higher affinity for CO2 than O2. 2. Carbonic anhydrase is present in RBCs. 3. Most CO2 is transported as bicarbonate. Which are correct? MCQ with Answer and Explanation

Explanation:
The thymus is a lobulated lymphoid organ located in the upper part of the thoracic cavity, near the heart. It is most prominent and active during childhood and begins to atrophy (involute) after puberty. Its primary function is to provide a microenvironment for the differentiation, selection, and maturation of T-lymphocytes (T cells), which are crucial for cell-mediated immunity. The thymus also secretes hormones like thymosin, which aid in T-cell development.

Explanation:
pUC19 is a small, high-copy-number cloning vector. A crucial feature for selecting recombinant clones is the presence of the lacZ' gene, which codes for the alpha-peptide of beta-galactosidase. The multiple cloning site (MCS) is located within this lacZ' gene. When foreign DNA is inserted into the MCS, it disrupts the lacZ' gene (insertional inactivation). On media containing X-gal and IPTG, colonies with empty vectors turn blue, while colonies with recombinant plasmids (disrupted lacZ') remain white, allowing easy visual selection.

Explanation:
The bottleneck effect is a form of genetic drift that occurs when a population's size is drastically reduced for at least one generation due to a severe environmental event (like a natural disaster, disease, or overhunting). The surviving population is a random, small sample of the original, and its gene pool may not represent the original population's genetic diversity. This leads to a significant loss of genetic variation, making the population more vulnerable to future changes.