Final answer:
Roundup kills plants by inhibiting the synthesis of aromatic amino acids through the active ingredient glyphosate, which disrupts the shikimate pathway.
Step-by-step explanation:
The mechanism by which "Roundup" kills plants is by inhibiting the synthesis of aromatic amino acids, specifically by disrupting the production of phenylalanine, tyrosine, and tryptophan. This process is crucial for plant growth and survival. The active ingredient in Roundup, glyphosate, targets the shikimate pathway, which is not present in animals but essential in plants. Furthermore, some crops have been genetically engineered to be resistant to glyphosate. This is done by incorporating a gene from Agrobacteria, resulting in 'Roundup Ready' seeds that can still synthesize the necessary amino acids even in the presence of the herbicide.