Basic genetics questions?

Question

You crossed a petunia plant with red flowers to a petunia plant with white flowers. the seeds from this cross produced plants that all had red flowers. When the seeds obtained by selfing these plants were grown, the plants produced either red flowers or white flowers in the ratio 3:1. Based on protein analysis, an enzyme called "protein A" was isolated from the red flowers. This protein was not present in the white flowers.

Give the genotype with regards to flower color for the plants: parentals, F1, and F2s.
How would you isolate the gene for protein "A"?
How would you determine the number of copies of this gene in the genome of petunia? Do you think you will find some form of this gene in the white flowered petunia plant?
What experiments would you do to determine if this gene is transcriptionally or translationally regulated at an organ/cell-specific manner?
Knowing what you know, can you design an experiment to validate that the gene you have isolated does encode for a protein that has a function in red pigment synthesis (petunia can be transformed)?

If you know any of those, could you answer and maybe explain why? I am lost on this one which my professor considers "basic", so maybe I am missing something simple. Thanks!

Anonymous · Accepted Answer

First, let's assign letters to the gene. 

R = red. It is dominant to white, which we will assign as r
Having at least one R means the flower will be red. Since white is recessive, it must be rr. 
One gene is received from each parent

So the parents yielded only red flowers. So the red flower had to be RR, or homozygous dominant. The white flower was rr.
The first generation was Rr and red, so they are heterozygous
When F1 is selfed, there will be a ratio of flowers. 25 percent will be RR, 50 percent Rr, and 25 rr.

This is all mendelian genetics, so I'll give you a site about it for reference.
http://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel1.htm

Isolating the gene. You can use a primer, which is a DNA sequence complimentary to the enzyme. The enzyme will bind to this DNA so it is the only gene you'll get.

You can see how many times the nucleotides in the sequence repeat. There is probably an inactive form in the white plant because they are related. And also because red plants are selected for (my guess) since more pigment would attract pollinators 

Transcription = DNA to RNA, Translation = RNA to protein. Does the Gene have RNA or DNA nucleotides? That would tell you what form it is in. 
A site on transcription and translation:
http://learn.genetics.utah.edu/content/begin/dna/transcribe/

You could isolate the gene and place it in bacteria. If the bacteria becomes red, it's pretty strong evidence.

Hope this helps

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Basic genetics questions?

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