Which of the following is a good primer sequence for PCR? A: A 25-bp oligonucleotide with a Tm of 56 degree B: A 30-bp oligonucleotide which can form a hair-pin structure C: A 50-bp oligonucleotide with a Tm of 55 degree D: A 30-bp oligonucleotide with a Tm of 72 degree

Which of the following is correct about the gene chip? A: It can simultaneously analyze the variation of multiple genes. B: Microarray sample density is very small. C: It can be used to study the expression of multiple genes. D: It is a regularly arranged cDNA or oligonucleotide array.