Question

The Human Genome Project has demonstrated that in humans of all races and nationalities approximately 99.9 percent of the sequence is the same, yet different individuals can be identified by DNA fingerprinting techniques. What is one primary variation in the human genome that can be used to distinguish different individuals? Briefly explain your answer.

Short answer

Answer: The primary variation in the human genome that can be used to distinguish different individuals is the presence of Single Nucleotide Polymorphisms (SNPs), which occur when a single nucleotide base (A, T, C, or G) varies between individuals. SNPs can be used in DNA fingerprinting by comparing patterns of SNPs between individuals, as the likelihood of the same SNPs occurring in the same pattern becomes increasingly low, allowing for the identification of unique genetic 'fingerprints' for each person.

Step-by-step solution

Introduction to the Human Genome

The human genome is the complete set of genetic information for humans, encoded within our DNA. It is mainly composed of sequences of four bases: adenine (A), guanine (G), cytosine (C), and thymine (T). These base sequences encode the information needed to build and maintain a human being. Understanding the variations within these sequences can be used for DNA fingerprinting techniques to distinguish between individuals.

Primary Variation in the Human Genome

One primary variation in the human genome that can be used to distinguish different individuals is the presence of Single Nucleotide Polymorphisms (SNPs). SNPs are positions in the DNA sequence where a single nucleotide base (A, T, C, or G) varies between individuals. These variations occur approximately once in every 1,000 nucleotides, which results in roughly 3 million to 4 million SNPs in the human genome.

How SNPs can be used in DNA Fingerprinting

SNPs help to distinguish individuals by providing a unique 'fingerprint' of an individual's genetic makeup. If researchers identify multiple SNPs within an individual's DNA, the likelihood of those same SNPs occurring in the same pattern in another person becomes increasingly low. Therefore, comparing patterns of SNPs can establish whether two DNA samples originated from the same individual.

Key concepts

Human Genome Project

The Human Genome Project (HGP) was an international research effort to determine the sequence of the human genome and identify the genes it contains. Initiated in 1990 and completed in 2003, the project aimed to map all the nucleotides contained in a set of human DNA. This pivotal project not only provided a comprehensive blueprint for building a human being, but it also laid the foundation for advances in genetic testing, gene therapy, and personalized medicine.

Due to the complexity of the human genome, which consists of over 3 billion DNA base pairs, the HGP utilized cutting-edge genomic sequencing techniques, which have since evolved significantly. This tremendous endeavor highlighted the fact that humans share the vast majority of their genetic sequence, with about 99.9% similarity across the species, affirming the unity of human biology across the globe. Yet, as the HGP revealed, it is the subtle differences in our DNA that contribute to our individual uniqueness, as well as our susceptibility to diseases.

Single Nucleotide Polymorphisms (SNPs)

Single Nucleotide Polymorphisms, or SNPs (pronounced 'snips'), are one of the most common types of genetic variation among people. A SNP represents a difference in a single DNA building block, called a nucleotide. For example, a SNP may replace the nucleotide cytosine (C) with the nucleotide thymine (T) in a certain stretch of DNA.

SNPs occur normally throughout a person’s DNA. They are found approximately every 300 to 1,000 bases along the 3-billion-base human genome. What makes SNPs incredibly valuable for genetic research is their frequency and distribution throughout the genome. These variations can serve as biological markers, helping scientists locate genes associated with disease. When SNPs occur within a gene or in a regulatory region near a gene, they may directly affect gene function, hence influencing the individual's health, physical attributes, or response to medication.

Genetic Variation

Genetic variation refers to the diversity found within the genetic makeup of individuals within a population. The variation is what makes each person unique and can affect everything from appearance to susceptibility to diseases. While the majority of DNA is identical across humans, the small percentage that varies is incredibly important.

Several types of genetic variation exist, with SNPs being just one example. Others include structural variations like insertions, deletions, and copy number variations, where sections of the genome can be duplicated or missing. Genetic variation is not only crucial for individual identification but also for the evolution of species, as it forms the basis for natural selection to act upon.

Genomic Sequencing

Genomic sequencing is the process of determining the complete DNA sequence of an organism's genome at a single time. This technique involves sequencing the order of nucleotides in a genome—the order of As, Ts, Cs, and Gs that make up an organism's DNA. Since the Human Genome Project's completion, the technology has rapidly evolved, and sequencing has become faster and more affordable.

Today, genomic sequencing is used for a variety of applications in medicine, such as identifying genetic disorders, characterizing cancer mutations, and determining the appropriate treatment for diseases based on an individual's genetic makeup. The information gained from genomic sequencing can also be used for evolutionary studies, as well as for understanding genetic relationships between individuals and populations.