Answer:
Single nucleotide polymorphisms (SNPs) are single base DNA differences that occur at specific locations on the human DNA. SNPs are the most common type of genetic variation among individuals and are responsible for the differences in traits and susceptibility to diseases.

Single Nucleotide Polymorphisms (SNPs)
- SNPs are variations in a single nucleotide (A, T, C, or G) at a specific position in the DNA sequence.
- They can occur in both coding and non-coding regions of the genome.
- SNPs can be inherited from parents or arise as de novo mutations.
- They can affect gene function, protein structure, and susceptibility to diseases.

Locations on Sites in the Human DNA
- The human genome is composed of approximately 3 billion base pairs.
- Within the genome, specific locations or sites can be identified where SNPs occur.
- These locations are typically referred to as SNP sites or SNP loci.
- SNP sites are specific positions on the DNA sequence where variations in a single base can be observed.

Identification of SNP Sites
- SNP sites can be identified through various methods, such as DNA sequencing or genotyping.
- DNA sequencing involves determining the exact order of nucleotides in a DNA molecule.
- Genotyping involves identifying specific variations at known SNP sites using methods like polymerase chain reaction (PCR) or DNA microarrays.

Significance of SNP Sites
- SNP sites are of significant interest in genetics and genomics research.
- They serve as genetic markers for mapping disease susceptibility genes.
- They can be used to study population genetics, human evolution, and ancestry.
- SNPs can also be associated with drug response and personalized medicine.

Conclusion
In summary, locations on sites in the human DNA where single base DNA differences occur are known as SNP sites. These sites are of great importance in genetics research, as they contribute to genetic variation among individuals and can have implications for disease susceptibility, drug response, and other traits.