Outline of genetics : with special reference to plant material / by Merle C. Coulter.

Abstract

been the actual history of the case, for, with the beginning of the twentieth century, the study of evolution culminated in, and became diverted into, genetics, the experimental study of inheritance. Of course genetics has not answered all of the questions that have presented themselves in connection with evolution, but many critical and suggestive findings have been made, as will be seen in the following chapters; and unquestionably genetics will contribute a great deal more in the next few decades. CHAPTER II THE INHERITANCE OF ACQUIRED CHARACTERSAt the basis of genetics lies the fact that variation occurs in all living organisms. It is possible to classify variations in a number of different ways.^At the outset it is important to realize the distinction between nonheritable and heritable variations. As for the former, it is usually evident that these originate as responses on the part of the organism to environmental stimuli. Acquired characters of this sort, however, are of little significance in genetics, inasmuch as they are not passed on from parent to offspring. It is the heritable variations that provide the material of genetics; and the origin of these is a matter of considerable controversy. For the most part, they are ascribed to mutation, meaning that their origin is sudden and spontaneous, seemingly unrelated to environmental stimuli. There is some evidence, however, which suggests that heritable variations may originate as acquired characters. It will be appropriate at this point to discuss the controversy on inheritance of acquired characters.The idea of inheritance of acquired characters was first clearly developed by Lamarck in connection with his explanation of evolution, the so-called theory of *' appetency," or the effect of use and disuse. Francis Galton, in 1875, was one of the first to express skepti-* A serviceable set of classifications is provided by Babcock and Claussen (i).

Stereochemistry of nucleic acids and their constituents. XIV. Crystal and molecular structure of 2,4-dithiouridine monohydrate

“…The bond angles in the base are quite similar to the values observed in 4-thiouridine (Saenger & Scheit, 1969), thymidine (Young, Tollin & Wilson, 1969) and the other 5-substituted bases such as 5-methyluridine (Hunt & Sabramanian, 1969), 5-fluoro-2'-deoxyuridine (Harris & Maclntyre, 1964) and 5-chlorouridine (Coulter, 1969). The exocyclic angles involving the C-S bond are remarkably close to the values found in the corresponding keto compounds.…”

The structure of a uridine derivative in the syn conformation: 6,7-dimethyl-N-1-β-D-ribofuranosyllumazine

“…Similar values for the same angle were observed in 6-methyluridine, 69.6 and 69.4 ° (Suck & Saenger, 1972), 3',5'-diacetyl-2'-deoxy-2'-fluorouridine, 68.5 o (Suck et al, 1974) and cytidine-2',3'-cyclophosphate, 62.9 and 74.5 ° (Coulter, 1973); in 4-thiouridine this angle is increased considerably to 92.9 ° (Saenger & Scheit, 1970). In Table 8 these torsion angles are listed together with the conformational angles within the ribose moieties.…”

“…Clearly the C(3')-endo envelope, which dominates in anti-nucleosides, is not preferred in syn-nucleosides but is replaced by a C(3')-endo,C(4')-exo twist form and by the C(2')-endo envelope which both appear to avoid unfavourable contacts between 0(2) and the H atom attached to C(3'). The ribose puckering for cytidine-2',3'-cyclophosphate (Coulter, 1973) differs from that of the other syn-nucleosides in Table 8, probably as a consequence of the fused phosphodiester group.…”

“…So far only a few pyrimidine nucleosides have * To'whom correspondence should be addressed. been observed in this conformation, namely cytidine-2',3'-cyclophosphate (Coulter, 1973), 4-thiouridine (Saenger & Scheit, 1970), 3',5'-diacetyl-2'-deoxy-2'-fluorouridine (Suck, Saenger, Main, Germain & Declercq, 1974), 6-methyluridine (Suck & Saenger, 1972). In this paper the structure of (I) is reported.…”

In-situ cyclic stress experiment at the Clinton P. Anderson Meson Physics Facility (LAMPF) for determining the effect of dislocation vibration on void growth in metals during irradiation. [Protons at LAMPF]

“…The experiment reported herein takes~dvantage of the high pcnetrntlng puwer of 800 MeV protons and pluces samples, one with an imposed cyclic stress, the other with no stress, In line along the proton baam to as~iureiden~ical irradiation hictories In both samples (Fig. 1) [4]. For Al, the damage energy cross section was found to be 63 barn-keV, and since the threshold displacement energy is 17 keV, the damage rate is (1) where dpa is displacements per atorn.…”