The Avery–MacLeod–McCarty experiment<span> was an experimental demonstration, reported in 1944 by </span>Oswald Avery<span>, </span>Colin MacLeod<span>, and </span>Maclyn McCarty<span>, that </span>DNA<span> is the substance that causes </span>bacterial transformation<span>, in an era when it had been widely believed that it was </span>proteins<span> that served the function of carrying genetic information (with the very word </span>protein<span> itself coined to indicate a belief that its function was </span>primary<span>).
It was the culmination of research in the 1930s and early 20th Century at the </span>Rockefeller Institute for Medical Research<span> to purify and characterize the "transforming principle" responsible for the transformation phenomenon first described in </span>Griffith's experiment<span> of 1928: killed </span>Streptococcus pneumoniae<span> of the </span>virulent<span> strain type III-S, when injected along with living but non-virulent type II-R pneumococci, resulted in a deadly infection of type III-S pneumococci.
In their paper "</span>Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III<span>", published in the February 1944 issue of the </span>Journal of Experimental Medicine<span>, Avery and his colleagues suggest that DNA, rather than protein as widely believed at the time, may be the hereditary material of bacteria, and could be analogous to </span>genes<span> and/or </span>viruses<span> in higher organisms.</span>
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In bryophytes, the sporophyte is minute and dependent on the relatively prominent and nutritionally independent gametophyte for resources. The moss gametophyte looks like a miniature herb, with tiny leaf-like photosynthetic organs. The gametophyte generation begins as a dormant spore, which germinates under appropriate conditions to produce filamentous and branching protonemal tissues. These form multicellular bud-like structures, each of which develops into a leafy shoot. The mature gametophytes produce male and female sexual organs, the antheridia and archegonia, respectively. The gametophyte is often sexually distinct, and plants are either male or female.
Each antheridium has an outer layer that encloses and protects thousands of motile sperm, which swim through available external water layer to the egg. Fertilization at the base of the cylindrical archegonium produces a diploid zygote which develops into an unbranched sporophyte. The sporophyte consists of a thin stalk attached to the gametophyte, and a capsule that encloses the sporophytic meiotic cells.
In recent years, the mosses Physcomitrella patens and Funaria hygrometrica have emerged as attractive model systems for studying gene function in non-vascular plants because of the relative ease of molecular manipulation by homologous recombination. Mutants affecting gametophyte development have been isolated and their analysis should provide insights into the molecular basis of gametophyte development in mosses.
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D) Mouth, pharynx, esophagus, stomach, small intestine, large intestine.
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Food is ingested in the mouth, passes through the pharynx that connects the mouth to the esophagus. It moves down the esophagus by parastalsis. It is further digested in the stomach, absorbed in the small intestine and indigestible material together with fibre is passed to the large intestine where its either digested by freindly bacteria or eliminated as waste by defecation.
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One very important chlorophyll is chlorophyll a. All photosynthetic organisms (except a few groups of bacteria) have this as their main photosynthetic pigment. It is important because only it can participate directly in the light reactions, which convert solar energy to chemical energy.
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