NEET 2023 question paper with solutions

1. Recall what happens to differentiated plant cells during tissue culture. Living differentiated cells, such as leaf mesophyll cells, have normally lost the capacity to divide.

2. Identify the process that lets them regain this ability. When placed in a culture medium under suitable conditions, these cells can regain the capacity to divide, and this reversal is called dedifferentiation.

3. Distinguish it from the other options. Differentiation is the opposite process (a cell becoming specialized), development refers to the overall growth of an organism, and senescence refers to aging — none describe cells regaining division capacity.

Hence, the answer is A. Dedifferentiation.

1. Check statement A.

Given that tetrad (bivalent) formation requires homologous chromosomes to pair up, and this pairing (synapsis) actually happens during zygotene, not leptotene, Statement A is false.

2. Check statement B.

Since during anaphase the centromeres holding sister chromatids together must split for the chromatids to move to opposite poles, this correctly describes anaphase.

So, Statement B is true.

3. Check statement C.

Given that terminalisation refers to chiasmata moving toward chromosome ends, and this occurs during diakinesis (the last sub-stage of prophase I), not pachytene, Statement C is false.

4. Check statement D.

Since the nuclear envelope, nucleolus, Golgi complex, and ER all reassemble once chromosomes reach the poles, this reformation happens during telophase.

So, Statement D is true.

5. Check statement E.

Given that crossing over is an exchange of genetic material between non-sister chromatids of homologous chromosomes (not sister chromatids, which are genetically identical), Statement E is false.

6. Combine the results.

Since only B and D are correct, the answer is Option A: B and D only.

1. Recall which organelles make up the endomembrane system. The endomembrane system includes organelles whose functions are coordinated together, namely the endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and the plasma membrane.

2. Examine why mitochondria (A) and chloroplasts (C) are excluded. Both organelles have their own separate double membranes and their own DNA, and are believed to have originated through endosymbiosis rather than from the ER-Golgi network, so they are excluded.

3. Examine why peroxisomes (E) are excluded. Although peroxisomes are membrane-bound organelles, they do not communicate with the other endomembrane organelles and are not involved in protein sorting or lipid synthesis like the true endomembrane components, so they too are excluded.

4. Confirm that endoplasmic reticulum (B) and Golgi complex (D) are true members. Both of these directly participate in the coordinated packaging and transport pathway, so they are part of the endomembrane system.

Hence, since A, C, and E are excluded, the answer is A. A, C and E only.