Intro to genetics problem.

[BioNoob]

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.

[JackBean]

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.

[jwalin]

bionoob
you have done an excellent job.
you have got the right answer

[jwalin]

@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

[JackBean]

So I was right, wasn't I?

[jwalin]

what's IMHO?
and you were wrong for once as they wanted how many would homologous dominant

[Omnesion]

IMHO = In my humble opinion.

[NeilC413]

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).

[JackBean]

if that means the same phenotype, than Pp will breed true in 75% of cases

[jwalin]

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

[jwalin]

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?

[JackBean]

OK, I didn't mention, that ALL of them must have the same phenotype...