Final answer:
The Polyadenylation sequences are located in the 3′ region of human genes and are important for mRNA processing and stability. Other sequences like promoters, splice signals, start codons, and locus control regions have different locations and functions within the gene structure.
Step-by-step explanation:
The sequence that is located in the 3′ region of human genes is the Polyadenylation sequences. These sequences are important for the processing of the pre-mRNA transcript into mature mRNA, which includes the addition of a 3′ poly-A tail. This tail is crucial for the stability of the mRNA and for its export from the nucleus to the cytoplasm, where translation occurs. The other options given, such as splice signals, promoters, start codons, and locus control regions, perform different functions and are located at various positions relative to genes. Splice signals are part of the pre-mRNA splicing machinery, while promoters are sequences where RNA polymerase binds to initiate transcription, typically found upstream of the transcription start site. Start codons mark the beginning of the coding sequence of a gene, whereas locus control regions are involved in the regulation of gene clusters and can be located far from the genes they regulate.