Geitonogamy is functionally cross pollination but genetically it is autogamy because in geitonogamy the pollens come from the same plant. Pollens are being transferred to the stigma of one flower to another flower of /on the same plant, which is genetically same. Therefore, geitonogamy is a cross pollination phenomenon but is equivalent to autogamy genetically. 

In artificially acquired passive immunity performed antibody in an immune serum is introduced into the body by infection. As the antivenum used to treat snake bites. In this case, the body does not produce any antibodies. Antibody is a protein molecule having two light chain and two heavy chain. B-cells recognize and bind antigens and may differentiate to memory cell or plasma cells (produce antibody). T-cells casues transplant rejection. 

Honey is made by bees by nectar and pollens. Bees collect pollen and nectar in the spring when most flowers and plants are in bloom. They collect them in their stomach about an hour,  the nectar mixes with the proteins and enzymes produced by bees, which convert nectar into honey.

In a palindrome, the base sequence in the second half of a DNA strand is the mirror image of sequence in first half. But in palindrome with rotational symmetry the base sequence in first half of one strand is mirror image of second half of complementary strand, e.g., 
5´ - GATACC - 3´
3´ - CCTAAG - 5´

Male gametes are flagellated in Ectocarpus belonging to Phaeophyceae. The flagella of male and gamete plays an important role in establishing initial sexual contact with the female gamete. However, in Ectocarpus the female gamete too is flagellated but is different in structure. 
In Polysiphonia (Rhodophyceae) flagellated gametes are not observed, in Anabaena sexual reproduction through gametes is absent while in Spirogya sexual reproduction takes place by conjugation wherein male gamete passes through a tube to the adjacent filament. The male gametes here are non-flagellated and show amoeboid movement. 

Gene therapy is the treatment of disease by the transfer and extension of genetic material in the patient's cell in order to restore normal cellular functions. The first clinical gene therapy was given for treating adenosine deaminase deficiency.

There are three steps in polymerase chain reaction namely.
(i) Denaturation- at  for DNA strand separation.
(ii) Annealing - binding of primer.
(iii) Extension in presence of DNA polymerase which is heat stable.