a. A LINE inserted into an enhancer of a human gene may result in consequences depending on which gene it is inserted and also depends on the insertion.
Here, the gene will not be expressed as no mRNA needs to be synthesized. This is because the insertion prevents the binding of transcriptional activators that are required for the ultimate binding of ribonucleic acid (RNA) polymerase to the promoter.
In more complex situations, the genes may be regulated by many enhancers. In most of the human genes, the genes are regulated by many enhancers. One enhancer may be required for transcription in the liver and other enhancer may be required for transcription in the muscle cells.
In this case, insertion of LINE into liver enhancer may prevent the transcription of that gene in the liver, but it will not interfere with the transcription of that gene in muscle cell.
b. The effects of insertion will depend on the gene that has sustained the insertion. In the simplest scenario, the insertion of the transposable element containing a binding site for a transcriptional repressor adjacent to a promoter, will prevent the binding of RNA polymerase II.
c. The Alu element will be transcribed into RNA with the rest of the gene sequences and will prevent the splicing of the intron that it has inserted into. As the Alu sequence and the intron will be translated, the insertion will result in a null allele. Alu and the intron both or one of them contains stop codons.
d. The insertion and excision of Ds element leaving 3 base pairs in the exon will result in a 3-bp indel (insertion and deletions) in the exon and slightly alter the amino acid sequence of the protein, but it will not produce a frame shift mutation. There will be a minor change in the amino acid sequence. This may affect the function of the encoded protein or sometimes there may not be any effects.
e. The insertion and excision of Ds element leaving 2 bp in the exon will produce a frame shift mutation and will impair the protein function more than the insertion and excision of Ds element leaving 3 bp.
f. A Ds element that was inserted into the middle of an intron and excises imperfectly and leaves 5 bp in the intron will not affect the gene expression, as the intron will be spliced during RNA splicing and it will be spliced correctly.