Extraction of DNA
All living organisms are composed of cells that contain
(deoxyribonucleic acid) and
, the fourth kind of biomolecule.
Nucleic acids contain the hereditary
information of the cell. In eukaryote cells, like humans, spinach and mushrooms, DNA forms discrete
contained within a membrane-bound
. In prokaryotic cells, like bacteria, DNA is in
a circular form and there is no nucleus.
Each species has a known number of chromosomes, for example
humans have 46 (23 pairs), dogs have 78, cats 38, horses 64, wheat 42, rye 14 and cauliflower 18.
chromosomes are called
(2N), 1 chromosome comes from each parent during fertilization.
contain only half of the chromosome content of the zygote and are called
Many plants, though, don’t always follow the haploid/diploid rule.
Most wild strawberries have 14
chromosomes (1N = 7).
Throughout centuries scientists and gardeners have cultivated new species and
hybrids of existing species.
These species include tetraploids (4N), hexaploids (6N) octaploids (8N) and
In general these polyploidy species are more robust plants with larger fruits, one of the
primary reasons they have been selected for.
Why grow tiny plants when you can grow bigger, healthier
ones in the same space?
And gigantic strawberries will surely sell for more at the grocery store!
The most common cultivated strawberry,
, is an
, 112 chromosomes.
propagated through asexual reproduction, cuttings and runners, to maintain the continuity of its DNA.
Although it can undergo sexual reproduction, thus the seeds (actually achenes) that are found on the
outside of the berry, strawberry farmers want to maintain the exact genetic makeup from one generation
to the next.
Kiwi fruit (
) also contain a lot of DNA, but it is due to a large haploid chromosome
Recent research to increase the size (and marketability) of kiwi fruit has resulted in the
observation of tetraploids (116 chromosomes) and hexaploids (174 chromosomes).
Biochemistry of DNA