Gen. Biology...NEED HELP ASAP

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Specializes in ICU. Med/Surg: Ortho, Neuro, & Cardiac.

My final exam for general biology is in 3 hours and I still have one question that I can't seem to answer on my review. I have to pass the final to get credit for the class. The question is...

"What is an example of evolution using genetics?"

To which I answered,

"A large number of houseflies died after the introduction of DDT; most houseflies born today have a resistance to DDT."

For reference, DDT is the chemical in bug spray that kills bugs.

My instructor has already told me via E-Mail that my answer is right but he wants me to show genotypes. I totally sucked at the chapter with genotypes and phenotypes. Can someone help?

Thanks!

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Specializes in ICU. Med/Surg: Ortho, Neuro, & Cardiac.

Thanks for the site. It's a good reference.

Now that I understand genotype more, I'm still having a hard time "showing the genotype." I don't know if that is like...

XXDD = male resistant to DDT

XYDD = female resistant to DDT

XXDD x XYDD

And then do the punnet square or whatever. I asked him for help on that part and he said he can't help me. No one in my class is available right now.

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I don't know what he means by "showing the genotype."

Is the Punnett square the Mendelian square?

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Okay, I did a little poking around via Google and these types of questions want the Punnett square shown.

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Specializes in ICU. Med/Surg: Ortho, Neuro, & Cardiac.

I don't think we covered Mendelian Squares, so I guess he's looking for a punnet square.

Ack, so lost. How would I cross maternal and paternal if I don't know if they carry the DDT-resistance gene, if they don't carry it, etc.?

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I don't think we covered Mendelian Squares, so I guess he's looking for a punnet square.

Ack, so lost. How would I cross maternal and paternal if I don't know if they carry the DDT-resistance gene, if they don't carry it, etc.?

Well, at least one of them has to carry it if it's a dominant trait, both if it's recessive. Right?

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The Punnett square is what I call the Mendelian square, Jared.

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Specializes in ICU. Med/Surg: Ortho, Neuro, & Cardiac.

DD x dd

D D

d Dd Dd

d Dd Dd

Maybe? But I still don't know if the gene is dominant or recessive in mother or father.

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You have to make it up, Jared.

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Specializes in ICU. Med/Surg: Ortho, Neuro, & Cardiac.

Well, does the monohybrid cross above look alright to you? The father has the dominant gene.

Thanks so much for the help.

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The one on the preceding page? Yes.

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