小中大准确地说,楼主的小鼠IL-4引物所扩增片段的大小应该为:
1、以RNA反转录所得的cDNA为模板,扩增产物为216bp(403-188+1)。
>gi|10946583|ref|NM_021283.1| Mus musculus interleukin 4 (Il4), mRNA
Length=605
Score = 40.1 bits (20), Expect = 0.089
Identities = 20/20 (100%), Gaps = 0/20 (0%)
Strand=Plus/Plus
Query 1 TCGGCATTTTGAACGAGGTC 20
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Sbjct 188 TCGGCATTTTGAACGAGGTC 207
Score = 40.1 bits (20), Expect = 0.089
Identities = 20/20 (100%), Gaps = 0/20 (0%)
Strand=Plus/Minus
Query 26 GAAAAGCCCGAAAGAGTCTC 45
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Sbjct 403 GAAAAGCCCGAAAGAGTCTC 384
2、以基因组DNA为模板,扩增产物为4586bp(91574-86989+1)
>gi|3687208|gb|AC005742.1| Mus musculus chromosome 11, BAC clone CT7-111I18 (LBNL M01),
complete sequence
Length=159500
Score = 40.1 bits (20), Expect = 0.089
Identities = 20/20 (100%), Gaps = 0/20 (0%)
Strand=Plus/Plus
Query 26 GAAAAGCCCGAAAGAGTCTC 45
||||||||||||||||||||
Sbjct 86989 GAAAAGCCCGAAAGAGTCTC 87008
Score = 40.1 bits (20), Expect = 0.089
Identities = 20/20 (100%), Gaps = 0/20 (0%)
Strand=Plus/Minus
Query 1 TCGGCATTTTGAACGAGGTC 20
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Sbjct 91574 TCGGCATTTTGAACGAGGTC 91555
对于所设计的引物,上游引物应该与模板序列某段完全相同、下游引物应该与模板序列的某段完全互补。下面看看用你的引物序列BLAST的结果,Identities后面的是引物序列与基因序列某段的匹配程度(如,100%),Query后面的是用于BLAST的引物序列,Sbjct后面的是与引物序列匹配的基因的某段序列。从BLAST结果可以看出,你的上游引物与小鼠IL-4基因序列的某段完全相同(注意上面的红色部分);你的下游引物与小鼠IL-4基因序列的某段互补且完全匹配(注意上面的蓝色部分)。