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Gregor Mendel is often referred to as the father of modern genetics — he developed the laws of Mendelian inheritance in the 1800s and advanced our understanding of how inheritance works .”
Brassica oleracea is a well-known example of this type of selective breeding . In its original form it is known as wild cabbage , but human intervention through breeding has led to a variety of domesticated forms . There are different varieties of Brassica oleracea in much the same way as there are different breeds of dogs , although it is generally better known by its various common names :
• Brassica oleracea bred for loose leaves is better known as kale .
• Brassica oleracea bred for large tight headed leaves is better known as cabbage .
• Brassica oleracea bred for small tight headed leaves is better known as Brussels sprouts .
• Brassica oleracea bred for large stems is better known as kohlrabi .
• Brassica oleracea bred for their edible immature flowers has resulted in cauliflower , broccoli , romanesco , and so on .
All of these were bred just by selecting for certain traits over many generations . A problem with this level of basic plant breeding is unexpected results can occur . If at least some of the underlying mechanisms involved are understood , then a breeding program can be much more efficient and predictable .
Mendelian Genetics
Gregor Mendel is often referred to as the father of modern genetics — he developed the laws of Mendelian inheritance in the 1800s and advanced our understanding of how inheritance works . This type of classical breeding is commonly used to improve the existing population of plants into new varieties . In our hypothetical red and white flowered plant example , flower color is a trait dictated by the gene for flower color .
The value of the gene is dictated by two alleles . Each parent will have two alleles , which may or may not be the same . They will pass on one or the other ( random chance ) to each of their offspring . When a seed is formed , for every gene , one allele is inherited from the pollen ( on the father ’ s side ) and the other from the egg ( on the mother ’ s side ). For the flower color gene , let ’ s call the red allele ‘ R ’ and the white allele ‘ r ’.
True Breeding Traits
If a red-flowering father is true breeding ( homozygous ) for red flower color , then both of his alleles are the same ( in this case coded for red ). For simplicity , this can be expressed as RR , one R for each of his two alleles . Since both of his alleles are for red flowers , he will have red flowers , and no matter which allele he passes on to his children , it will be an allele for red flowers ( because it will either be an R or the other R ). The same is true for homozygous mothers . If a white-flowering mother is true breeding for white flower color , then both of her alleles are the same , but this time coded for white . For simplicity , this can be expressed as rr . When she produces seeds , she will donate either her first r or her second r , but an r in either case . Again , the same would be true for homozygous fathers . The parent generation is called the P generation . When two members of the P generation are crossed , the resulting children are members of the F1 generation . The children of the F1 generation are called the F2 generation , their children are the F3 generation , and so on . If both members of the P generation are true breeding for red flowers , then the offspring will all have red flowers .
Cross-pollination Selfing
Transfer of pollen with brush
Removal of anthers
Transfer of pollen to stigma
Progeny Progeny
46 Maximum Yield