Most bacteria have a haploid genome, a single chromosome consisting of a circular, double stranded DNA molecule. However linear chromosomes have been found in Gram-positive Borrelia and Streptomyces spp., and one linear and one circular chromosome is present in the Gram-negative bacterium Agrobacterium tumefaciens.

Bacteria with multiple chromosomes have been found in diverse prokaryotic phyla including Actinobacteria, Chloroflexi, Deinococcus-Thermus, Fibrobacteres, Firmicutes, Proteobacteria (α-, β- and γ-classes), and Spirochaetes, suggesting that they have arisen independently, many times in the course of evolution.

Like other organisms, bacteria use double-stranded DNA as their genetic material. However, bacteria organise their DNA differently to more complex organisms. Bacteria have a single circular chromosome that is located in the cytoplasm in a structure called the nucleoid.

Chromosomes vary in number and shape among living things. Most bacteria have one or two circular chromosomes. Humans, along with other animals and plants, have linear chromosomes that are arranged in pairs within the nucleus of the cell.

The amount of DNA in bacterial chromosomes ranges from 580,000 base pairs in Mycoplasma genitalium to 4,700,000 base pairs in E. coli to roughly 9,450,000 base pairs in Myxococcus xanthus.

The human genome is comprised of 23 pairs of linear chromosomes, and approximately 3000 megabases (Mb) of DNA, while the genome of the bacterium Escherichia coli consists of a single 4.6 Mb circular chromosome.

It is common knowledge that bacteria, or even viruses and fungi, exist in areas of our body, including the mouth, skin and gut.

“You share 50 percent of your DNA with each of your parents. But with bananas, we share about 50 percent of our genes, which turns out to be only about 1 percent of our DNA,” emails Mike Francis, a Ph. D. student in bioinformatics at the University of Georgia.

Analysing your DNA enables you to trace its origin and discover where your ancestors came from. An ethnicity estimate shows how similar your DNA is to different populations from around the world. The higher the degree of similarity, the higher the likelihood of your common origin.

The simplest thing DNA can tell you is whether someone is male or female. Apart from some very rare cases, that doesn’t even involve looking at their DNA sequence – all you need to know is whether they have X and Y chromosomes (making them male) or a pair of Xs (which makes them female).

One of the most enduring is that a man inherits the baldness gene from his mother. While there is some truth to this, it is not the whole story. The primary baldness gene is on the X, or female chromosome, which men do inherit from their mothers.