Question

Do morphogens support a preformation or epigenetic view of development? Provide an example to support your answer.

Answer 1

Epigenetic is the study of changes which is heritable character and become reversible without any changes in the DNA sequences or gene sequences. In developmental biology this epigenetic changes occur by morphogen gradient. Morphogen is the gradient of gene of expression in tissue. This morphogen can regulate the expression of tissue in developmental period of an organism. But this morphogen is not responsible for any kind of gene alteration. Morphogen regulate the pattern formation in an organism. In early period of development morphogen differentiate the cells in a specific manner. Morphogen provide information gradient to the cell and this information is received by specific cell receptor. This reaction can regulate by which manner one celll can determine their pattern formation of particular organ. There is a threshold level of this concentration gradient. cells which are closer to the source of morphogen receive high concentration the morphogenic infomation and differentiate the cell in a specific manner. But the cells far from source of morphogen receive low concentration of information and differentiate the same cells in different manner.

An example is found in Drosophila pattern formation where same gene in the cells express differently by different morphogen gradient but there is no alteration of DNA sequences. In early development of Drosophila Bicoid gene expression occur in anterior part of the organism and this gene control development of anterior structure of the organism. Where as Caudal gene expression is seen in the posterior part of the organism which control posterior structure develpoment. Thus in an organism every cells contain same gene but from this same cells different organs develop because these cells receive different morphogenic information.