Genetics vs. Genomics
Genetics and genomics are closely connected, but they do not focus on exactly the same level of biological information.
Genetics generally focuses on individual genes, inheritance, mutations, and relationships between genes and traits.
Genomics takes a broader approach by studying large portions of, or the entire, genome.
What Is a Genome?
A genome contains the genetic information of an organism. In humans, the genome is primarily composed of DNA organized into chromosomes.
A genome contains:
- Genes
- Regulatory sequences
- Non-coding DNA
- Repetitive regions
- Genetic variants
- Chromosomal structures
The human genome contains billions of DNA base pairs, with the sequence of these bases providing the information studied by genetic and genomic researchers.
How Is the Genome Organized?
Genomic information can be understood at several interconnected levels:
DNA → Genes → Chromosomes → Genome
DNA is the molecule that stores genetic information. A gene is a region of DNA associated with a functional product, such as a protein or functional RNA. DNA is organized into chromosomes, and the complete collection of genetic material forms the genome.
Genomes also contain regulatory and other non-coding regions that contribute to how genetic information is organized and used.
Understanding this organization is important because genomic research does not simply ask what DNA sequence is present? It also asks how different genomic regions function and interact.
Understanding Genetic Variation
Genomes differ between individuals, populations, and species. These differences are known as genetic variation.
Variation can include:
- Single-nucleotide variants
- Insertions and deletions
- Copy-number variations
- Structural variations
- Larger chromosomal changes
Some variants may have little or no known biological effect, while others can influence biological characteristics or contribute to disease.
DNA sequencing allows researchers to identify genetic differences by comparing DNA sequences with reference genomes or with other samples.
How Do Scientists Study Genomes?
Studying a genome involves much more than simply reading DNA.
A simplified genomic research workflow can include:
Biological sample → DNA/RNA extraction → Library preparation → Sequencing → Quality control → Computational analysis → Variant or feature identification → Biological interpretation
Depending on the research question, scientists may use different approaches, including:
- DNA sequencing
- RNA sequencing
- Whole-genome sequencing
- Whole-exome sequencing
- Genotyping
- Comparative genomics
- Functional genomics
- Metagenomics
The choice of method depends on what researchers want to investigate.
The NCBI Handbook provides information about NCBI resources covering genomes, variation, genes and gene expression, nucleotide and protein databases, and bioinformatics tools.
DNA Sequencing and Next-Generation Sequencing
DNA sequencing determines the order of nucleotide bases in DNA. Sequencing technologies have developed considerably over time, allowing researchers to analyze increasingly large amounts of genetic material.
Next-generation sequencing (NGS) refers to high-throughput sequencing technologies that can generate large quantities of sequence data. NGS has become an important tool for studying genomes, transcriptomes, genetic variants, and biological processes.
Researchers can use NGS for applications such as:
- Whole-genome sequencing
- Whole-exome sequencing
- Targeted sequencing
- RNA sequencing
- Variant discovery
- Microbial genome analysis
- Cancer genomics
Whole-Genome Sequencing and Whole-Exome Sequencing
Two important genomic approaches are whole-genome sequencing (WGS) and whole-exome sequencing (WES).
Whole-Genome Sequencing
WGS aims to analyze DNA across the entire genome. Because it covers both coding and non-coding regions, it can provide a broad view of genomic variation.
Whole-Exome Sequencing
WES focuses primarily on the exome, the collection of protein-coding regions of the genome.
The choice between WGS, WES, and targeted sequencing depends on the research question, sample type, available resources, and the type of genomic information being investigated.
The Role of Bioinformatics in Genomics
Genomic sequencing can produce extremely large datasets. Bioinformatics provides computational methods for organizing, processing, analyzing, and interpreting these data.
A genomic analysis may involve:
- Quality control
- Sequence alignment
- Genome assembly
- Genome annotation
- Variant detection
- Gene expression analysis
- Sequence comparison
- Database searches
- Statistical analysis
NCBI provides numerous databases and computational resources for working with genomic and biological data. Its resources include information on genomes, variation, genes and gene expression, nucleotide sequences, proteins, and biological literature.
