Biology (Medical Entrance) - 5

Transposons are also called jumping genes as they can jump or transpose to different locations in the genome of a single cell.

 This option is correct because epinasty means downward, differential growth of the upper or adaxial part of a plant organ. Auxin and ethylene are involved in this response.

Auxotrophs require external addition of those components, which they are unable to synthesise.

Schwann cells wrap nerve cell axons in the peripheral nervous system with layers of myelin (a type of plasma membrane that provides electrical insulation).

This option is correct because nictitating membrane is also known as plica semilunaris.

This option is correct because in the presence of ultraviolet rays, rhodopsin breaks down and this process is known as bleaching.

 This option is correct because phototropism is directional growth in which the direction of growth is determined by the direction of the light source. In other words, it is the growth which response to a light stimulus.

This option is correct because geotropic responses in the roots occur due to more growth on the upper side of the root.

 Boyer and Cohen invented the DNA cloning technique that gave birth to an important branch of science called genetic engineering.

This option is correct because chemotaxis is the phenomenon in which somatic cells, bacteria and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment.  In multicellular organisms, chemotaxis is critical to early development (e.g. movement of sperm towards the egg during fertilization) and subsequent phases of development (e.g. migration of neurons or lymphocytes) as well as in normal function. 

This option is correct because auxins are a class of plant growth substances and morphogens (often called phytohormone or hormone). Auxins have an essential role in coordination of many growth and behavioural processes in the plant's life cycle.

In a frog, the number of cranial nerves are ten pairs.      

 This option is correct because the movement of cytoplasm is termed as cyclosis or cytoplasmic streaming.

This option is correct because movement of plant in response to an external stimulus is known as tropism. One of this stimulus can be a source of light to which the plants show response by bending. This process is known as phototropism.

In human brain, cerebral hemispheres are connected by corpus callossum.

The centre of autonomic nervous system is located in hypothalamus. 

 Beadle-Tatum worked on Neurospora crassa to show that one gene is responsible for producing one enzyme.

 Stop codons are nucleotide triplets in m-RNA indicating termination of the process of translation.

This option is correct because geotropism is the movement of plant growth in response to the direction and force of gravity.

This option is correct because the leaflet of Oxalis exhibits hyponasty. Hyponasty is the increased growth of the lower surface of a plant part, resulting in an upward bending of the part.

This option is correct because the chemical stimuli causing the movement of antherozoids towards the egg are malic acid and sugar.

The innermost layer of meninges which is very close to brain is piamater.

The part of human brain which controls hunger, thirst and sleep is hypothalamus.

Malleus is the first bone, incus is the second and stapes is the third bone from tympanum to inner ear.

In human brain, the most abundant cell type is the glial cells.