Final answer:
A ratio lower than 1.8 at 260/280 nm indicates substantial protein contamination in a nucleic acid sample, potentially affecting downstream applications such as PCR or sequencing.
Step-by-step explanation:
When analyzing nucleic acids, the Absorbance ratio at 260/280 nm is used as an indicator of protein contamination. A ratio between 1.8 and 2.1 suggests that the sample mainly contains nucleic acids without significant protein contamination. If the ratio is lower than 1.8, it usually indicates that there is substantial protein contamination in the nucleic acid sample. This may affect downstream applications, such as polymerase chain reactions (PCR) or sequencing, as proteins can interfere with the efficiency and accuracy of these techniques. When interpreting absorbance values, aspects such as the presence of phenol or other contaminants that could also absorb at these wavelengths must be considered.