Punnet Squares - I have some blue flowering plants and some green flowering plan
ID: 91890 • Letter: P
Question
Punnet Squares
- I have some blue flowering plants and some green flowering plants of the same species. I planted the seeds after cross pollinating them. Wow! I got the coolest looking teal colored flowers. Before you read any further, what could be responsible for this? Being the nerd that I am, I have a microscope at home (I really do!). I took a petal of one of these teal flowers and looked at it under the microscope. What I found were really tiny blue dots and really tiny green dots. When viewed from a distance, the green and blue dots make the flower look teal. Does this change the answer you came up with in the first question? From a distance, what two possibilities would come to mind-explain how you arrived at this conclusion?
- I know a farmer who grew pumpkins for Halloween with really long stems (this is true-I know this farmer). His customers loved them since they could easily create an easy to manipulate cap for lighting and extinguishing the candle. He wanted to grow the really warty ones, but the warty ones have short stems. He figured he would cross pollinate the long stemmed pumpkins with the warty ones then plant the seeds from this crossing and see what he gets. To his surprise, he got about half with long stems and warty skin and half with long stems and smooth skin. Explain the reason for these phenotypes. Hint: Examine the two phenotypes separately then give your answer for both phenotypes.
Explanation / Answer
Let us consider your first question “Before you read any further, what could be responsible for this?”
We can represent the flower color as
Blue – BB and Green – GG
Parents BB X GG
Gametes B G
F1 BG (teal)
On crossing blue colored flower plant with green, we obtained the progeny as teal which is neither green nor blue but a mixture of both. This shows that there was the occurrence of incomplete dominance.
In incomplete dominance, both genes of contrasting characters express as a blend and the result of it is such that the hybrid produced by crossing the two pure individuals does not resemble either of them but a midway between them. Therefore, one allele of a trait is not completely expressed or dominant over its paired allele.
For the second part of your question “Does this change the answer you came up with in the first question?” it is totally a different phenomenon.
Let us represent the flower color in a different way (to avoid confusion) as
Blue - FB FB and Green - FG FG
Parents FB FB X FG FG
Gametes FB FG
F1 FB FG (teal with both the colors expressed)
In this case, both blue and green colors of the flowers of F1 generation were fully expressed. This phenomenon wherein the alleles of a gene pair in a heterozygote is fully expressed is called co-dominance. This results in offsprings with a phenotype that is neither dominant nor recessive.
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