Answer:
increasing extension time
Explanation:
The Polymerase Chain Reaction is a technique widely used in molecular biology laboratories to amplify target DNA regions. The standard steps of a PCR are as follow 1-denaturation, 2-annealing and 3-elongation/extension. These steps are repeated 15-40 times in order to exponentially amplify the linear DNA fragment. It is well known that longer extension times can be used as a strategy to increase the yield of longer PCR products. This is because the extension time depends on the synthesis rate of the DNA polymerase used in PCR technique and the length of the DNA fragment to be amplified.
Answer no 1:
The part labelled A is the upper epidermis . The main function of the epidermis is to protect the structure of the leaf.
The part labelled B is palisade tissues. These are the sites where the chlorophyll are present.
The part labelled C are the air spaces in the spongy mesophyll tissue. They allow carbon dioxide to move freely.
The part labelled D are the vascular tissues which transport water and food.
Answer No 20:
The correct option is B) Most of the carbohydrates are made in the palisade mesophyll.
The palisade mesophyll comprises of chloroplast which are the sites where photosynthesis takes place. Hence, these will be the sites where carbohydrates will be manufactured.
Answer No 21)
The correct option is A) upper epidermis
As upper epidermis is the first layer of leaf, sunlight will enter through it and be trapped by the chlorophyll present in the palisade mesophyll cells.
Sources of heat from inside earth is radioactive decay and residual heat.
They respire and give off c0^2
