Gene sequencing and genome projects

In a nutshell

Gene sequencing is used to analyse genetic material found in an organism. This can be collated in gene projects to map the entire genome of an organism.

Genome projects

Genome projects aim to map the nucleotide sequence that make up an organism's genome. This can then be used to map the genes onto the chromosomes of the organism. With this information, tools can be developed to identify genes involved in diseases.

Example

The Human Genome Project began in $1990$ and it was completed in $2003$ . The project aimed to map all $3.2\ billion$ base pairs and $20,000$ genes.

Bioinformatics plays a vital role in genome projects. Bioinformatics is the science of collecting and using computers to analyse biological data.

Gene sequencing

Definition

Gene sequencing is a method used to determine the nucleotide sequence in a gene. Gene sequencing can be used to map a whole genome using whole-genome shotgun (WGS) sequencing. This involves cutting the DNA into small fragments, using bioinformatics to align overlapping sequences, then assembling the whole genome.

SNPs

Single nucleotide polymorphisms (SNPs) are single-base variations in the genome. These are often associated with diseases and genetic disorders. Gene sequencing identified $1.4\ million$ SNPs in the human genome. This knowledge can be used to easily screen individuals and ascertain their risk of developing certain diseases.

Proteome

Definition

An organism's proteome is the complete set of proteins that can they can express at a given time (as genes for proteins can be switched on or off under certain conditions).

It is easier to determine the proteome of simple organisms, like bacteria, as they have less non-coding DNA than complex organisms, like humans.

Determining genomes and proteomes

Simple organisms

Simple organisms are easier to map as they have fewer genes and less non-coding genetic material.

Example

The complete genome of the bacterium Haemophilus influenzae consists of $1.8\ million$ bases and $1700$  genes. The mapping of the genome was completed in $1995$ . 

A benefit of determining the genome and proteome of simple organisms, like bacteria, is that antigens can be identified on their surface. These can be used in vaccine development.

Complex organisms

The Human Genome Project mapped all $20,000$ protein-coding genes in the human genome. Determining the genomes and proteomes of complex organisms is more difficult given the large amount of non-coding DNA.

Example

Up to $99\%$ of human genes are non-coding.