In the DNA strand, guanine bonds to cytosine. It does not bond to the other nitrogenous bases. Guanine and cytosine form three hydrogen bonds to keep complementary strands of DNA together.

One of the primary differences between purines and pyrimidines is that purines consist of two rings, whereas the pyrimidines consist of one ring. One way to help remember the differences between purines and pyrimidines is that pyrimidines are like pyramids: sharp. Sharp things CUT (Cytosine Uracil Thymine). Note that uracil is only present in RNA, while thymine is only present in DNA. All nitrogenous bases bond to the sugar in the DNA backbone. The sugar is also connected to a phosphate group via a phosphodiester bond.

Purines are adenine and guanine, while pyrimidines are cytosine, thymine, and uracil.

The hnRNA (heterogeneous nuclear RNA) produced from transcription must be processed by several enzymes to create an mRNA (messenger RNA) product that can pass from the nucleus to the cytoplasm without degrading. This involves cutting out introns, which remain in the nucleus, and splicing exons together. Furthermore, a methylguanine cap is added to the 5' end and a poly-A tail is added to the 3' end. 

Addition of a 5-methyl guanosine cap, the splicing out and removal of introns, and the addition of a poly-A tail are all processes that are essential to making stable, mature mRNA.

Codons are contained on the exons of mature mRNA and are matched to appropriate anticodons during translation. Anticodons are found on tRNA molecules, and are not involved in mRNA transcription.

Fingerprints are different in all individuals, even identical twins. Due to RNA processing, or post-transcription modification, the grooves of a finger are different even in individuals with identical DNA.

The other techniques are used for DNA analysis between individuals with different DNA. Identical twins will be indistinguishable under these techniques, because their DNA is the same.

During post-transcriptional modification, spliceosomes can remove introns from the transcript and splice together exons. Introns are the parts that are removed from the transcript, meaning they are not translated. Exons are the portions of mRNA that code for the correct amino acids sequence for the desired gene.

Other modifications involve the poly-A tail, which is added to the 3' end, and the 5' cap. Both structures protect the transcript from damage during transport and provide binding sites for various proteins, as well as the ribosome itself. Methylation is a part of epigenetic DNA modification, and is not involved with transcription processes.

snRNPs, or small nuclear ribonucleoproteins, are an essential part of the spliceosome complex. The spliceosome is responsible for the removal of introns from the primary transcript.

Post-transcriptional modifications are changes that are made to the mRNA transcript before it is translated into a protein. The first of these changes is cleavage at the 3' end to separate the new strand, or "primary transcript," from the transcription machinery. Next, a protective 5' cap is added, as is a string of adenine nucleotides at the 3' end. Finally, noncoding regions, called introns, are spliced out and the exons, or coding regions, are reconnected.

The incorrect statement confuses exons and introns.

Post-transcriptional modification is the stage where the recently synthesized primary RNA transcript undergoes changes to become a mature RNA molecule. Post-transcriptional modifications ensure that the correct RNA transcripts are produced and that the correct proteins are translated. Post-transcriptional modification includes the processes of polyadenylation, 5’ capping, and splicing. Polyadenylation is the addition of adenine bases (the poly-A tail) to the 3’ end of the RNA primary transcript. The poly-A tail is important in export, stability, and translation of the transcript. 5’ capping is the addition of guanine bases to the 5’ end of the primary transcript. The 5’ cap aids in export and translation of the transcript and also protects it from degradation. Splicing is the removal of non-coding regions, or introns, from the primary transcript.