The results of some of Gregor Mendel’s experiments up to the F2 progeny or first selfed progeny (S1) are summarized in the table below.
The symbol F1 for the first filial generation refers to Mendel’s “hybrids” while F2 or second filial generation refers to his first generation after the hybrids.
Summary of Gregor Mendel’s Data
Table GM-2. Summary of Gregor Mendel’s data on the characters of the F1 and F2 progenies using garden pea as test plant (source: Mendel 1865).
Characters Evaluated | Parental Cross | F1 Phenotype | Total F2 Progeny Evaluated | Numbers of F2 Progeny | F2 Phenotypic Ratio (dominant to recessive character) |
Form/shape of ripe seed | round x wrinkled | round or roundish (smooth) | 7,324 seeds from 253 F1 plants | 5,474 round or roundish seeds, 1,850 wrinkled | 2.96:1 |
Color of cotyledons | yellow x green | yellow | 8,023 seeds from 258 F1 plants | 6,022 seeds with yellow cotyledons, 2,001 green | 3.01:1 |
| Color of seedcoats* (and flowers) | grey-brown x white seedcoats | grey-brown seedcoats, violet-red flowers | 929 F2 plants | 705 plants produced violet-red flowers and grey-brown seedcoats, 224 white flowers and white seedcoats | 3.15:1 |
| Form of ripe pods | inflated x constricted | inflated | 1,181 F2 plants | 882 plants had inflated pods, 299 constricted | 2.95:1 |
| Color of unripe pods | green x yellow | green | 580 F2 plants | 428 plants had green pods, 152 yellow pods | 2.82:1 |
| Position of flowers | axial x terminal | axial | 858 F2 plants | 651 plants had axial inflorescences, 207 terminal | 3.14:1 |
| Length of stem | long x short | long | 1,064 F2 plants | 787 plants had long stems, 277 short | 2.84:1 |
MEAN** | 2.98:1 |
* Violet-red flowers develop into seeds with grey-brown seedcoats; white flowers into white seed coats.
** The average ratio of the dominant to the recessive character in the F2 progeny was 2.98:1 or 3:1.
Gregor Mendel’s Interpretation of Results
Each of the hybrids (F1) showed the character of one parent only which he called dominant.
The character of the other parent, however, is not lost but is only hidden (or masked).
This character, called recessive, reappeared in the next generation (the F2 progeny) but in a ratio of one in every four plants whereby the other three plants exhibit the dominant character.
This means a ratio of 1:3 recessive to dominant characters or, reversed, 3:1 dominant to recessive characters.
Mendel explained that the dominant phenotypes in the F2 consisted of two types: those representing the pure dominant parental character (homozygous for the dominant character), and those having the hybrid character (heterozygous).
He further distinguished that the progeny possessing the pure dominant parental character will yield offsprings having the same character while those with the hybrid character will produce diverse offsprings (exhibiting dominant and recessive characters) similar to what had been observed in the F2 progeny (i.e., 3:1 dominant to recessive characters).
Note: There is no way to tell if any F2 plant (or seed) showing the dominant character is a pure dominant (with homozygous genotype) or a hybrid (with heterozygous genotype).
The F2 seeds and the seeds harvested from the F2 plants had to be planted before a determination can be made.
Number of Plants Evaluated
The above table shows that Gregor Mendel obtained his data from a total of 5,123 plants.
Out of these, 511 were F1 plants that he evaluated for the form or shape of ripe seeds (253 plants) and for the color of cotyledons (258 plants).
The remaining 4,612 were F2 plants that he evaluated for the other five sets of characters.
REFERENCE
MENDEL G. 1865. Experiments in Plant Hybridisation. (Translated by the Royal Horticultural Society of London). Retrieved Nov. 2, 2013, from https://ia600409.us.archive.org/15/items/experimentsinpla00mend/experimentsinpla00mend.pdf.
