Biology MCQs

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Apomixis is reproduction where only one parent passes genes to the offspring. Apomictically produced offspring are genetically identical to the parent (clones). The method is most seen in plants, especially flowering plants. Brambles (blackberry) are apomictic. Some authorities give “reproduction by special tissues without fertilisation”, or “asexual formation of a seed from the maternal tissues of the ovule, avoiding meiosis and fertilization, leading to embryo development”. (Wikipedia Simple)

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As cells develop some genes are turned off permanently. All of the cells within a complex multicellular organism such as a human being contain the same DNA; however, the body of such an organism is clearly composed of many different types of cells. What, then, makes a liver cell different from a skin or muscle cell? The answer lies in the way each cell deploys its genome. In other words, the particular combination of genes that are turned on (expressed) or turned off (repressed) dictates cellular morphology (shape) and function. This process of gene expression is regulated by cues from both within and outside cells, and the interplay between these cues and the genome affects essentially all processes that occur during embryonic development and adult life. This means that cells become specialized because the genes that are not required are switched off. Only the genes needed to make a particular type of cell work are switched on. So muscle cells only have the genes needed to make muscle cell proteins switched on. All the other genes, such as those needed to make blood cell proteins and nerve cell proteins, are switched off. But the stem cells are unspecialized and can develop into various tissues.

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The chemical name of Vitamin B3 is Niacin which is a water soluble vitamin. It is an important nutrient. In fact, every part of your body needs it to function properly. As a supplement, niacin may help lower cholesterol, ease arthritis and boost brain function, among other benefits.

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Water is passively transported into the roots and then into the xylem. The forces of cohesion and adhesion cause the water molecules to form a column in the xylem. Water moves from the xylem into the mesophyll cells, evaporates from their surfaces and leaves the plant by diffusion through the stomata.

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Scratching helps to relieve an itch because it reduces the sensations of pain sent to the brain, a new study has found. Scientists found that skin cells in that part of the body tended to respond more to itchy substances than those in other areas.

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The genus of the human being today is called Homo and the man today is called as Homo sapiens. From simple life forms that were unicellular to the development of multicellular organisms gave rise to the vertebrates. The family to which human beings belong is called Hominidae. It was in the Miocene age that the family Hominidae split from the Pongidae(apes) family.

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Vitamin E was discovered by Evans and Bishop in 1922. Work in the 1930s revealed the chemical structure and biological function of alpha-tocopherol.

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Multiple layer of peptidoglycan that helps to retain the crystal violet stain is happens in Gram-positive cells. Gram-positive organisms have a thicker peptidoglycan cell wall than Gram-negative bacteria.

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The stimulating growth factor was found to be cytokinin, a hormone that promotes cell division.

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The nucleus of the pollen tube and the secondary nucleus of the egg develop in the endosperm.