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Joined: 11/19/2005
Posts: 30460
Posted on Sunday, July 23, 2006 6:24:20 PM
 
Ok, using Mendilean Symbols, the cross is:

PpYyRr x Ppyyrr

Need to calculate the fraction of offspring predicted to exhibit the recessive phenotypes for at least 2 of the 3 traits. Listing all
genotypes that fulfill this condition:

ppyyRr, ppYyrr, Ppyyrr, PPyyrr and ppyyrr.

We use the rule of multiplication to calculate the individual probabilities for each of these genotypes from our PpYyRr x Ppyyrr cross.
Finally we use the rule of addition to pool the propabilities for fulfill the condition of at least two recessive traits:

ppyyRr 1/4 (propability of pp) x 1/2(yy) x 1/2(Rr) = 1/16
Я не понимаю, почему именно 1/4 ? Откуда она взялась? I'm a slow thinker today :( В классе вроде бы всё понятно было, а тут :-/

ppYyrr 1/4 x 1/2 x 1/2 = 1/16

Ppyyrr 1/2 x 1/2 x 1/2 = 2/16

PPyyrr 1/4 x 1/2 x 1/2 = 1/16

ppyyrr 1/4 x 1/2 x 1/2 = 1/16

Почему рр постоянно 1/4 а все остальные 1/2 ?

Chance of at least 2 recessive traits = 6/16 or 3/8
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"[I] don't care just what people say:
If I should take a notion to jump into the ocean- Nobody's business
If I go to church on Sunday then cabaret on Monday-Nobody's business"
Last edited by lady bastet on Sunday, July 23, 2006 6:27:00 PM
 
Joined: 8/6/2004
Posts: 5983
Posted on Sunday, July 23, 2006 6:36:35 PM
 
Потому, что в исходном выражении PpYyRr x Ppyyrr с обоих сторон есть набор Рр, а остальные наборы имеют разные пары Yy и yy, Rr и rr, соответственно. :)
Joined: 11/19/2005
Posts: 30460
Posted on Sunday, July 23, 2006 6:38:42 PM
 
«Потому, что в исходном выражении PpYyRr x Ppyyrr с обоих сторон есть набор Рр, а остальные наборы имеют разные пары Yy и yy, Rr и rr, соответственно. :)»

Спасибо огромное :))))))
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"[I] don't care just what people say:
If I should take a notion to jump into the ocean- Nobody's business
If I go to church on Sunday then cabaret on Monday-Nobody's business"
Joined: 11/19/2005
Posts: 30460
Posted on Sunday, July 23, 2006 6:46:49 PM
 
Нее, тогда почему Рр только 1/2 ?

Ppyyrr 1/2 x 1/2 x 1/2 = 2/16

Like I know there are only 2 of them at the beginning: PpYyRr x Ppyyrr

but.......


Ыыыы, крап.
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"[I] don't care just what people say:
If I should take a notion to jump into the ocean- Nobody's business
If I go to church on Sunday then cabaret on Monday-Nobody's business"
Last edited by lady bastet on Sunday, July 23, 2006 6:50:00 PM
 
Joined: 8/6/2004
Posts: 5983
Posted on Sunday, July 23, 2006 6:51:31 PM
 
По той же самой причине. Рр (исходный набор) - 1/2, а РР и рр по 1/4. :)
Joined: 11/19/2005
Posts: 30460
Posted on Sunday, July 23, 2006 6:55:20 PM
 
ЫЫыыыыыыыыыыыыыыыыы ( плакает)

вроде дошло, ща ещё раз перекручу в голове.
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"[I] don't care just what people say:
If I should take a notion to jump into the ocean- Nobody's business
If I go to church on Sunday then cabaret on Monday-Nobody's business"
Joined: 7/22/2006
Posts: 134
Posted on Sunday, July 23, 2006 8:44:48 PM
 
predpolagaetsa chto oni na raznih alleles? togda shans recessive P(A)=1/2,P(b)=1/2, i P(c)=1/4, gde a,b,c eti 3 raznih genes. Chto bi poluchit 2/3 recessive, nado P(A&B)orP(B&C)orP(A&C)orP(A&B&C)
t.e. .5*.5+.5*.25+.5*.25+.5*.25*.25
Joined: 7/22/2006
Posts: 134
Posted on Sunday, July 23, 2006 8:45:46 PM
 
now tell me about stalking.
Joined: 11/19/2005
Posts: 30460
Posted on Sunday, July 23, 2006 8:51:07 PM
 
чё-та ты меня запутал совсем, я только врубилась, а ты... :)
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"[I] don't care just what people say:
If I should take a notion to jump into the ocean- Nobody's business
If I go to church on Sunday then cabaret on Monday-Nobody's business"
Joined: 7/22/2006
Posts: 134
Posted on Sunday, July 23, 2006 8:56:05 PM
 
voobsche to ya kazhetsa ne pravdu skazal, ya schas prochitau esche raz
Joined: 7/22/2006
Posts: 134
Posted on Sunday, July 23, 2006 9:00:10 PM
 
net ya pravilno vse skazal. no drugoe obyasnenie kotoroe ya hotel dat' tolko zaputalo bi. a to chto ya napisal vse verno. naprimer P(A) eto veroyatnost' chto budet yy P(B) chto budett bb i t.d. tebe nado chto b bilo yybb ili yypp i t.d.
Joined: 11/19/2005
Posts: 30460
Posted on Sunday, July 23, 2006 9:05:02 PM
 
did u take genetics?
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"[I] don't care just what people say:
If I should take a notion to jump into the ocean- Nobody's business
If I go to church on Sunday then cabaret on Monday-Nobody's business"
Joined: 7/22/2006
Posts: 134
Posted on Sunday, July 23, 2006 9:07:10 PM
 
da, eto high school genetics
Joined: 11/19/2005
Posts: 30460
Posted on Sunday, July 23, 2006 9:09:03 PM
 
Ну я тут не училась в хай скул.
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"[I] don't care just what people say:
If I should take a notion to jump into the ocean- Nobody's business
If I go to church on Sunday then cabaret on Monday-Nobody's business"
Joined: 7/22/2006
Posts: 134
Posted on Sunday, July 23, 2006 9:13:25 PM
 
ya dumal v rossii high school slozhnee?
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