(A) (B) anterior posterior () (D) Figure Q21-3 Effects of Dpp expression on wing development in Drosophila (Problem 21-16). (A) Normal Dpp expression. (B) Absence of Dpp expression. (C) Additional anterior Dpp expression. (D) Additional posterior Dpp expression. (From M. Zecca, K. Basler and G. Struhl, Development 121:2265-2278, 1995. With permission from The Company of Biologists.)
Gene Interactions
When the expression of a single trait is influenced by two or more different non-allelic genes, it is termed as genetic interaction. According to Mendel's law of inheritance, each gene functions in its own way and does not depend on the function of another gene, i.e., a single gene controls each of seven characteristics considered, but the complex contribution of many different genes determine many traits of an organism.
Gene Expression
Gene expression is a process by which the instructions present in deoxyribonucleic acid (DNA) are converted into useful molecules such as proteins, and functional messenger ribonucleic (mRNA) molecules in the case of non-protein-coding genes.
The extracellular protein factor Decapentaplegic
(Dpp) is critical for proper wing development in Drosoph-
ila (Figure Q21–3A). It is normally expressed in a narrow
stripe in the middle of the wing, along the anterior–pos-
terior boundary. Flies that are defective for Dpp form
stunted “wings” (Figure Q21–3B). If an additional copy
of the gene is placed under control of a promoter that is
active in the anterior part of the wing, or in the posterior part of the wing, a large mass of wing tissue composed of
normal-looking cells is produced at the site of Dpp expres-
sion (Figure Q21–3C and D). Does Dpp stimulate cell divi-
sion, cell growth, or both? How can you tell?
