Gene expression in eukaryotes can be regulated at various levels. certain mutations in flies may cause them to develop an extra set of legs or wings. a. small interfering rna b. operons c. hox genes, which determine the formation and arrangement of body parts in multicellular organisms, control gene expression by regulation of a. pre mrna splicing b. mrna degradation c. dna description. nextreset

The right answers are: C. Hox Genes and C. DNA description (it's better to say transcription).

Hox genes are among the most extensively studied genes in evolutionary biology. Hox genes are a special category of homeotic genes. The homeotic genes have a DNA sequence described as homeotic or homeobox. Moreover their name, "Hox", comes from the contraction of "homeobox".

The homeobox will encode a homeodomain in translated proteins. These proteins are transcription factors (type of genetic regulatory protein) that, thanks to their homeodomain with a particular conformation, allows them to bind strongly to the DNA and allows cascade activation of other genes.

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.