Chromosomal Anomalies as the Cause of Developmental Disorders

Abstract

Many instances have been found in plants and animals where both abnormal development and the transmission of hereditary characters were associated with chromosome anomalies. Bridges (1916) discovered the presence of an additional chromosome in the genome to be responsible for the anomalous transmission of certain characters in the fruitfly Drosophila. He attributed the abnormal chromosome constitution to be the result of non-disjunction of a particular chromosome during gametogenesis. Similarly in Datura plants, the presence of an extra chromosome in the genome produced new morphological varieties. Blakeslee (1922) demonstrated that the different appearance or phenotype of the new varieties depended on which particular chromosome of the genome was “extra”. Since that time an impressive amount of information concerning chromosome behaviour in plants and animals has been brought together by cytologists showing that the genetic behaviour of an organism can be inferred and predicted through chromosomal studies.