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Intro to genetics problem.

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Intro to genetics problem.

Postby BioNoob » Tue Jan 19, 2010 9:17 am

I am unsure that my answer to this problem is correct please help me.

In the plant datura, purple flowers are dominant to white flowers. When a purple-flowered plant is self-pollinated, its progeny are 28 purple-flowered plants and 10 white-flowered plants. What proportion of the purple-flowered progeny plants will breed true if they are self-fertilized?

Since the progeny are in a 3:1 ratio, I got Pp x Pp as the crosses. So the ratio of the crosses are 1PP, 2Pp, 1pp. Since it asks the proportion of the purple flowered progeny plants of true, I took out the recessive pp and got 1/3 PP and 2/3 Pp. So I got 1/3 as my answer.
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Postby JackBean » Tue Jan 19, 2010 12:07 pm

Question is, what is meant by breeding true...

Anyway, you have correct the genotypes, but IMHO, they are asking, how much of P2 will be purple again.
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby jwalin » Wed Jan 20, 2010 1:16 am

bionoob
you have done an excellent job.
you have got the right answer
it isn't what you do that matters but it is how you do it
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Postby jwalin » Wed Jan 20, 2010 1:20 am

@jackbean
bread true means you get a homologous recessive or dominant when one of the parent is the has the genetic constitution as the offspring

a little confusing. sorry. i will get back to you
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Postby JackBean » Wed Jan 20, 2010 12:13 pm

So I was right, wasn't I?
http://www.biolib.cz/en/main/

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Postby jwalin » Wed Jan 20, 2010 3:11 pm

what's IMHO?
and you were wrong for once as they wanted how many would homologous dominant
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Postby Omnesion » Sat Jan 23, 2010 4:51 am

IMHO = In my humble opinion.
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Re: Intro to genetics problem.

Postby NeilC413 » Tue Feb 02, 2010 8:03 am

Original post is correct. Also "breeding true" means your offspring are all the same phenotype as you. So you must be a homozygous genotype (PP or pp).
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Postby JackBean » Tue Feb 02, 2010 8:33 am

if that means the same phenotype, than Pp will breed true in 75% of cases ;)
http://www.biolib.cz/en/main/

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Postby jwalin » Tue Feb 02, 2010 3:26 pm

okay
let's get things clear

the definition is
A phenotype for a simply-inherited trait is said to breed true if two parents with that phenotype produce offspring of that same phenotype only

i.e PP or pp

simple


sorry, even i was wrong

the right answer is 1/3
Last edited by jwalin on Wed Feb 03, 2010 3:52 pm, edited 1 time in total.
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Postby jwalin » Tue Feb 02, 2010 3:27 pm

and
A kind of breeding in which the parents with a particular phenotype produce offspring only with the same phenotype
this is the definition on
http://www.biology-online.org/dictionary/True_breeding

a new website for us all no?
:roll:
:x
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Postby JackBean » Tue Feb 02, 2010 4:23 pm

OK, I didn't mention, that ALL of them must have the same phenotype...
http://www.biolib.cz/en/main/

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