Introduction:
The Northern blotting technique is a laboratory method used to study gene expression by detecting and analyzing specific RNA molecules. It involves separating RNA molecules based on their size and then detecting the presence and quantity of a specific RNA molecule. While the technique is useful for certain types of information, there are limitations to what can be determined using Northern blotting.

Explanation:
a) The strand of DNA that is transcribed into mRNA:
This information can be determined using the Northern blotting technique. The technique involves isolating RNA molecules from a sample and then subjecting them to gel electrophoresis to separate them based on their size. The resulting RNA bands can be transferred to a membrane and hybridized with a labeled DNA probe. By using a specific probe complementary to the DNA strand of interest, one can determine if that particular DNA strand is transcribed into mRNA.

b) The amino acid sequence of the protein coded by an mRNA species:
This information cannot be determined using Northern blotting. The technique only provides information about the presence and quantity of specific RNA molecules. It does not provide any information about the translation process that converts mRNA into a protein. Determining the amino acid sequence of a protein requires techniques such as protein sequencing or mass spectrometry.

c) The half-life of an mRNA species:
This information can be determined using the Northern blotting technique. By comparing the intensity of the RNA bands at different time points after transcription inhibition, one can estimate the half-life of an mRNA species. A decrease in the intensity of the RNA band over time indicates the degradation of the mRNA molecule and can be used to determine its half-life.

d) The size of an mRNA species:
This information can be easily determined using the Northern blotting technique. The technique involves separating RNA molecules based on their size using gel electrophoresis. By comparing the migration of the RNA bands with known size markers, one can determine the size of the mRNA species.

Conclusion:
In conclusion, the Northern blotting technique is a valuable tool for studying gene expression and analyzing specific RNA molecules. While it can provide information about the DNA strand transcribed into mRNA, the half-life of an mRNA species, and the size of an mRNA species, it cannot determine the amino acid sequence of the protein coded by an mRNA species. Other techniques such as protein sequencing or mass spectrometry are required to determine the amino acid sequence of a protein.