How is the structure, function and position of the crayfish nerve cord different from the rat's spinal cord?

In the crayfish's nerve cord, it is the combination of the two nerves that lead from the brain to form the ventral nerve cord which runs down the abdomen. It is important for sending signals from the ganglion to the appendages and muscles. While the rat's spinal cord it runs along the dorsal or back, rather than the front, and it is important for transferring neural signals between the brain and for the rest of the body.

C) to ensure each new cell has an exact copy of the dna

Proteins are the workhorses of the cell, controlling virtually every reaction within as well as providing structure and serving as signals to other cells. proteins are long chains of  amino acids  , and the exact sequence of the amino acids determines the final structure and function of the protein. instructions for that sequence are encoded in  genes  . to make a particular protein, a messenger ribonucleic acid (mrna) copy is made from the gene (in the process called  transcription  ), and the mrna is transported to the  ribosome  . protein synthesis, also called  translation  , begins when the two ribosomal subunits link onto the mrna. this step, called initiation, is followed by elongation, in which successive amino acids are added to the growing chain, brought in by transfer rnas (trnas). in this step, the ribosome reads the  nucleotides  of mrna three by three, in units called  codons  , and matches each to three nucleotides on the trna, called the anticodon. finally, during termination, the ribosome unbinds from the mrna, and the  amino acid  chain goes on to be processed and folded to make the final, functional protein