Any of the possible combinations of alleles will result in every member of the F1 generation getting an R from each of the two parents . The father will give one or the other of his two Rs and the mother will give one or the other of her two Rs , forming offspring that will have two Rs . The same would be true with white flowers . Two parents homozygous for white flowers will make offspring with white flowers . Where things start to get complicated is when a red-flowered pollen-bearing hypothetical plant and a white-flowered egg-bearing hypothetical plant are crossed together . The father will donate one of his two Rs , and the mother will donate one of her two rs , resulting in children that will all have one of each ( Rr ). This is the F1 generation ( in this case also the hybrid generation ). Since the offspring will have one R and one r , they are heterozygous for flower color .
Hybrid F1s
Two Rs form red flowers , and two rs form white flowers . What flower color the plants will have when they have one allele of both will depend on which is dominant . Alleles that win ties ( when there is one of each ) are called dominant , and those that lose ties are called recessive . So , if red is dominant , then the Rr children will all have red flowers . If white-colored flowers were dominant , then the F1 generation would all have white flowers ( there are also some cases where heterozygous alleles have what is called incomplete dominance that can result in things like pink flowers , but that is a more advanced topic ). F1 hybrids tend to be similar to each other and can exhibit a robustness that is called hybrid vigor . For this example , assume red flower color is dominant .
F2s
If two members of the F1 generation ( Rr ) are crossed ( say that three times fast ) then each parent will pass one of their two alleles . The four combinations possible in the F2 generation are RR , Rr , rR , and rr . These are commonly expressed as a punnett square .
• In the case of RR , the child plant will have red flowers .
• In the case of rR or Rr , the child plant will have red flowers ( because of dominance ).
• In the case of rr , the child plant will have white flowers .
In other words , about 75 percent of the offspring will have red flowers , and about 25 percent will have white flowers .
P
F1
F2
RR
Rr
RR Rr Rr rr
Breeding for recessive traits is easier than breeding for dominant traits . In the example , while there are fewer white flowers , they will all be rr ( because they didn ’ t have an R to lose to ). For the dominant trait however , RR , Rr , and rR will all have red flowers , and no way to tell them apart . With recessive traits , if they show , they are true breeding . With dominant traits , one has to run trials and use statistics to be able to determine when it is statistically likely to be homogeneous .
GMOs
While traditional forms of breeding have involved probability and record keeping to determine and change the alleles in an existing plant population , there are also more direct methods that can create genetically modified organisms ( GMOs ). By using genetic engineering techniques , the alleles are changed or replaced in the laboratory . Early methods included introducing a mutagen and observing the survivors for promising candidates . Later methods include using a gene gun and carrier viruses to alter ( or replace ) alleles . One concern with GMOs is they allow the resulting lifeforms to be patented / owned by the generating company that can have legal and social repercussions if they are allowed to become a major source in the public food chain ( or health ).
Gardeners
Many gardeners perform some form of classical breeding if for no other reason than to develop plants that are well suited to their own needs . It can be a fun and engaging hobby , if not one suited for instant gratification . With time and patience ( and a little know how ) progress can be made in home gardens , which can help with both diversity and disease defense .
rr
Rr
“ F1 hybrids
tend to be similar to each other and can exhibit a robustness that is called hybrid vigor .”
Maximum Yield 47