Textbook - N ON-DISJUNCTION A S PROOF O F T HE CHROMOSOME T...

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NON-DISJUNCTION AS PROOF OF THE CHROMOSOME THEORY OF HEREDITY1 CALVIN B. BRIDGES Colicmbia University, New York City [Received October 21, 19151 TABLE OF CONTENTS PALE I. IN~ODUCTIOX .............................................................. I The sex chromosomes and sex ........................................ z Normal sex-linked inheritance ......................................... 4 The characters used and their linkage relations. . ....... .:. ............. 4 Primary non-disjunction in the female. ................................. 9 11 11 11. NEW DATA ............................................................... 14 I5 16 secondary exceptions ................................................. 16 I7 18 XXY females ....................................................... I9 females ............................................................. 28 37 44 49 Primary non-disjunction in the male .................................... Secondary non-disjunction in the female. .............................. The percentage of secondary exceptions ................................ The equality of the exceptional sons and daughters of XXY females. .... The relation between the percent of heterosynapsis and the percent of The coefficient of Y synapsis ........................................... The relation between the coefficient of Y and the percent of exceptions Tihe equality of XXY and XX females among the regular daughters of The equality of XYY and XY moles among the regular sons of XXY Secondary non-disjunction in the male .................................. The constitution of the patroclinous sons of XXY females. ............ XO males and primary non-disjunction. The independence of non-disjunction. ................................ 45 Attempts to obtain pure stock of non-disjunction. ............................... ..................... I INTRODUCTION There has been a long series of observations and experiments which has led more and more definitely to the conclusion that the chromosomes are the bearers of the hereditary materiak2 It was observed that male and female contribute equally to the inheritance of the offspring, and yet the contribution of the male consists of little more than a nucleus. That *Contribution from the Zoological Laboratory of Columbia University. ‘For a huller discwssion of the steps in the accumulation of this evidence see “The mechanism of Mendelian heredity” by MORGAN, STURTEVANT, MULLER, and BRIDGES. GENETICS 1: Ja 1916
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2 CALVIN B. BRIDGES inheritance is a function of the nucleus rather than of the cytoplasm is shown by many embryological and cytological facts. Attention was next narrowed to the chromatin and chromosomes. Embryological experi- ments showed that the chromosomes are qualitatively different and that a full complement is essential to normal development. The increasing cytological knowledge of mitotic division and of gametogenesis made it clear that the chromosomes were qualified to serve as the material basis of heredity. The next advance was the result of the exact knowledge of heredity which Mendelian analysis furnished, and of the coupling of experimental genetics with cytological investigation. It was shown that the genes for characters and the chromosomes have the same Method of distribution. More recently cases have arisen in which genes and chromosomes have the same distribution. The final step has been to demonstrate the identity of distribution between spccijic gcnes and specific chromosomes in such a way that the argument of “the-cell-as-a-whole’’ cannot be ap- plied, and in such a way that the chromosomes must be regarded as the means and not the consequence of the inheritance of characters and of sex. The experimental and cytological evidence in the case of non-
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This note was uploaded on 04/04/2010 for the course MCB 164 taught by Professor Burgess during the Spring '08 term at UC Davis.

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Textbook - N ON-DISJUNCTION A S PROOF O F T HE CHROMOSOME T...

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