A woman plants 2 yellow plants next to each other in area with lots of soil that has nothing growing in it. Overall time (just as the woman hoped), the seeds from the plants fall in to the soil and make many more plants. To the surprise of the woman, about one fourth of the new plants are white. She is asking you, because she know you are taking biology, how is this possible? What would you tell her and be sure to include terms such as dominant, recessive and others that you have learned that may help her understand.

Answer 1

I would explain to her that the color of the plants is likely determined by genetics, specifically through the principles of inheritance established by Gregor Mendel. Here’s a breakdown of how she might see both yellow and white plants emerge from her initial two yellow plants:

1. Dominant and Recessive Traits: In genetics, traits are often described as dominant or recessive. Let's assume that yellow flower color (Y) is a dominant trait and white flower color (y) is a recessive trait.

2. Genotype of the Initial Plants: Since both of her initial plants are yellow, it is possible that their genotypes are either homozygous dominant (YY) or heterozygous (Yy). If a plant is homozygous dominant (YY), all offspring will be yellow. However, if both plants are heterozygous (Yy), their offspring can be a mix of yellow and white plants.

3. Punnett Square Analysis: If both yellow plants are heterozygous (Yy), we can set up a Punnett square to see the possible combinations of alleles in their offspring:

   | | Y | y | |-----|-----|-----| | Y | YY | Yy | | y | Yy | yy |

   In this case:

   • 1 out of 4 (25%) will be homozygous dominant (YY - yellow).
   • 2 out of 4 (50%) will be heterozygous (Yy - yellow).
   • 1 out of 4 (25%) will be homozygous recessive (yy - white).

   As a result, for every four offspring, you’d expect one to be white (yy).

4. Conclusion: This means that the appearance of white plants among the new generation is due to the combination of alleles inherited from the original yellow plants. Since she has white offspring, it is a strong indication that both of her yellow plants carried the recessive allele (y) for white flower color, making them heterozygous (Yy).

5. Genetic Diversity: This phenomenon also highlights the concept of genetic diversity and variability within populations, which can result from the combination of different alleles during reproduction.

I would assure her that the appearance of white plants is a normal and interesting part of plant reproduction and genetic inheritance!