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Properties of the DNA in a Strawberry

Strawberries only became a cultivated crop about 250 years ago. Scientists are now using modern techniques to study the genetics of strawberries; the genome of the woodland strawberry, Fragaria vesca, was first sequenced in 2010. This species is popular with gardeners. Much of what scientists learn about the genome of F. vesca will be applicable to the related species cultivated by farmers, F. ananassa, as well.

Chromosomes
- Both woodland and cultivated strawberries have seven chromosomes. Like humans, the woodland strawberry is diploid, meaning it contains two copies of each chromosome. The cultivated species, however, is octoploid, meaning it has eight copies of each, making it one of the most complex of crop plants. Organisms with more than two copies of each chromosome are sometimes called polyploid, and this type of phenomenon is more common among plants than animals. The genome of the woodland strawberry has about 250 million base pairs (compared to roughly 3 billion in the human genome or more than 16 billion in the onion genome).
Genes
- According to the Nature Genetics study that first announced the sequencing of the strawberry genome, there are thought to be as many 34,000 genes in the strawberry genome; humans have a number of genes between 20,000 and 25,000 for comparison. There are thought to be some 569 transfer-RNA encoding genes, 177 ribosomal RNA-encoding genes, and a couple hundred other genes that code for small RNAs (small nucleolar RNAs, micro RNAs, etc). Some 1600 or so of the protein-coding genes code for transcription factors, proteins that regulate or are involved in expression of other genes.
Chloroplast Genome
- In addition to the nuclear DNA, strawberries, like other plant species, also have DNA in their chloroplasts. The chloroplast genome of the woodland strawberry is about 155,000 base pairs in length and has 78 protein-coding genes, 30 transfer RNA-encoding genes and four ribosomal RNA-encoding genes. There is some evidence to suggest that DNA has been transferred from the chloroplast genome to the nuclear genome in the recent history of this species.
Day Neutrality
- While modern molecular methods will probably assist greatly in strawberry cultivation, the genetics of strawberries have already been studied to some extent using older methods. Day neutrality is an especially prized trait in strawberries, for example. A day-neutral plant forms flower buds under both short and long day conditions, so it increases the number of harvests farmers can produce each year. Multiple genes are involved in day-neutrality, although researchers have not yet identified them.

Nature