Possible Causes: Components · Primer concentration is too low. · Primer concentrations not balanced. Make sure primers are present in equal concentrations. · New primers are required. Some primers are immune to optimization. See Primer Design. · Nested primers are required. Reamplify dilutions (1:10 to 1:1000) of the first reaction using nested primers . · Contaminated primer. See Rescuing Contaminated PCR Primers and Wayward PCR Primers. · Template concentration is too low. Use a higher concentration of template. · Template concentration is too high. Excessive template can inhibit the reaction by binding all the primers . · Template is degraded. Check the integrity of the template by electrophoresis after incubation. · Template: Target sequence is not present in target DNA. Redesign your experiment or try other sources of target DNA. · Mg++ concentration is too low. This may compromise enzyme activity so try increasing the concentration by 0.2 mM · dNTP concentration is too low. Normally concentrations between 20 - 200 μM are optimal. · dNTPs degraded. Keep nucleotides frozen in aliquots, thaw quickly and keep on ice once thawed. Avoid multiple · pH of the reaction buffer is too high. · Reaction mixture is incomplete or degraded. Do a control check with positive control DNA. · Buffer isn't diluted enough. Add more water.Possible Causes: Conditions · Denaturing temperature is suboptimal. Try extending the time and/or increasing the temperature of the initial denaturation · Annealing temperature is too high. Start at 10° C below calculated optimal annealing temperature. · Suboptimal extension time. Increase by 1minute increments, especially for LA PCR. · Inhibitors are present. See Enhancers & Inhibitors in this Guide. · Enhancers needed. Some reactions may amplify only in the presence of additives. See Enhancers & Inhibitors in this · Mineral oil problem. The reaction must be overlaid with highquality, nuclease-free light mineral oil. Do not use autoclaved · Reaction tubes are contaminated. tubes eliminates contaminants that inhibit amplification. See also How to Reduce Contamination. · Too few cycles. Try doing 10 additional cycles at a constan annealing temperature (i.e. 55° C) and recheck. · Thermal cycler didn't cycle. Check to see if the thermal cycler was actually turned on. · Thermal cycler was programmed incorrectly. Check to see if times and temperatures are correct. · Thermal cycler temperatures are too low in some positions. Do a set of control reactions to determine if certain positions give · Thermal cycler top was left open. |
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