Experiment 2: You are happy that you have identified the molecular mechanism by

Question

Experiment 2: You are happy that you have identified the molecular mechanism by which the tomatoes become pink. You go to the company that produces these tomatoes to explain your data. However, when you explain your results, the company scientist tells you that the red and white alleles are not found in nature and that the pink and white tomatoes are genetically modified: He tells you that the company produced a knock-out construct which contained the C nucleotide at the 33^rd nucleotide in the promoter of the red gene. Then they transfected cells from red tomatoes with this construct and were able to knock-out the promoter region of the red gene. The construct inserted into the promoter site and since it contained the mutation the promoter became inactive. Importantly, he tells you that these experiments were not done using a single cell, but small tomato embryos containing many tomato cells were transfected with the construct. So maybe some cells were transfected and others were not. He also tells you that there was no positive selection but only negative selection. Upon these explanations you suspect that your earlier conclusions might have been wrong: You think that since they used many cells for transfections and no positive selection, some cells might have become heterozygous for the C allele (CT), other cells might have become homozygotes (CC), and some cells might not have the mutation at all, they could be TT homozygotes. To test if this is the case, you want to stain tomatoes transfected with the knock-out construct with a fluorescent antibody that binds only to the "red" protein. When you do this experiment you see that only some cells produce the red protein and others do not: so there are only two types of cells, red and white. To understand what is going on, you obtain 2 red and 1 white cells, you grow them separately so that they form clones. You then obtain DNA from all three clones and repeat the RFLP experiment above. You get the results shown below. Based on these observations, would you conclude that the red allele is dominant, co-dominant, or recessive over the "white" allele? Please explain your logic briefly. Red tomato cells: cells #1,2 White tomato cells: cells # 3

Explanation / Answer

The process here is explaining that the expressed pink color does not have any allele of its own.

The effect in the hybrid is intermediate between the two parents red and white.

CC is homozygous mutated for red gene

TT is homozygous non mutated for white gene

CTare heterozygous

Only two alleles CC / TT are present.

A crossing between these two resulted in incomplete dominance with pink allele expression in heterozygous condition.

The offspring thus do not exhibit any characters of parents in incomplete dominance.

Here the red is dominant over the white allele expressing intermediate color in heterozygous condition.

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.