genetics question

[mrdorky]

Hey
I am having trouble understanding how to solve genetics questions.
Need help with solving this one:

In a plant, blue petal (B) is dominant to white petal (b); and long stem (L) is dominant to short stem (l). Determine the parental genotypes if 299 blue petal long stem, 302 blue petal short stem, 103 white petal long stem, and 98 white petal short stem plants are produced.

A) BbLl x Bbll
B) BbLl x BbLl
C) BBll x BbLl
D) Bbll x bbLl
e) bbLl x bbLl

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[UCB05]

Hey
I am having trouble understanding how to solve genetics questions.
Need help with solving this one:

In a plant, blue petal (B) is dominant to white petal (b); and long stem (L) is dominant to short stem (l). Determine the parental genotypes if 299 blue petal long stem, 302 blue petal short stem, 103 white petal long stem, and 98 white petal short stem plants are produced.

A) BbLl x Bbll
B) BbLl x BbLl
C) BBll x BbLl
D) Bbll x bbLl
e) bbLl x bbLl

It's easier to round the numbers:
300 Blue, Long
300 Blue, Short
100 White, Long
100 White, Short

You can see there are 600 blues and 200 whites, 3:1 ratio. The minipunnet resulting in that ratio would be Bb x Bb.

Next there are 400 long plants and 400 short plants. The cross representing that would be Ll x ll

Considering the law of independent assortment you can conclude that the parent genotypes were BbLl x Bbll

If you wanted to use a full 2-gene punnet cross to figure this out, you would get the same answer as well, but it would take quite a bit longer.

 

[mrdorky]

ok that makes more sense than the solution to the answer.

Thanks a lot UCB05! =)

I always have trouble with these genetic problems... bleh

 

[dentalWorks]

great explanation UCB05