(This is the online version of the paper booklet available at ticket offices in the Garden.)
One complete copy of the DNA of an organism is called its genome. Sequencing genomes has revolutionised our understanding of evolution and how heredity works. This trail will explore the genomes of some familiar plants and reveal some of their evolutionary secrets.
Download the DNA in the Garden Trail brochure here.
What is DNA?
DNA (short for DeoxyriboNucleic Acid) is the material that stores the instructions for making the components of all living things and enables this information to be passed to future generations. It acts like an instruction manual for the organism.
DNA is composed of four basic building blocks called bases which are nitrogen-containing biological compounds. They form base pairs and stack on top of each other leading directly to the formation of the double helix DNA structure.
What are genes and genomes?
Genes are sections of DNA that contain the code for a particular trait or characteristic like eye colour. There are a number of different varieties of the same gene (known as alleles); so a gene coding for eye colour can code for blue, green, brown etc. Humans have up to 23 000 genes.
Genes are packaged together into spaghetti like structures called chromosomes which normally occur in pairs- half from one parent and the other half from the other parent; humans have 23 pairs of chromosomes. Many plant species, however, have more than two sets of each chromosome, this is known as their ploidy level.
One complete copy of the DNA of an organism, including bits that don’t code for anything, is called its genome. Genomes are measured in millions of base pairs (Mb=Mbp)= 1,000,000 bp.
The amount of DNA in a genome differs dramatically between species. Unwinding the DNA in a cell of the plant with the largest genome, the Fritillary, would stretch a staggering 84 metres, compared with just over 2 metres in our own genome.
Large amounts of DNA carry high inherent biological costs. The more DNA in an organism, the longer it takes to copy it. Plants with large genomes thus grow slower than their slim-genome relatives. This can restrict the type of life strategy that a plant adopts, for example whether it is an annual or perennial.
DNA sequencing involves determining the order of the DNA base pairs. Knowing the sequence for the entire genome of an organism and understanding what each gene codes for, allows us to understand the evolutionary history of a species and how organisms respond to their environment. The code can then be linked to traits, such as flower colour and shape, which are the manifestation of the genetic code in the living organism.
Ensembl Plants is a genomes database produced by EMBL’s European Bioinformatics Institute (EMBL-EBI) and holds the genomic data of many plant species, some of which have been highlighted in this trail.
For each plant species featured in this trail you will learn something about the size of their genome, their chromosome number and how many sets of chromosomes they have (you can learn more about this on the back page of this trail leaflet). In addition you will find out how sequencing the genome of these species has revealed their evolutionary secrets.