Login

Join for Free!
118478 members


BACKCROSS HELP

Discussion of all aspects of cellular structure, physiology and communication.

Moderator: BioTeam

Postby star21 » Fri May 13, 2005 5:00 pm

thank you
star21
Garter
Garter
 
Posts: 13
Joined: Wed May 04, 2005 10:07 pm

Postby star21 » Fri May 13, 2005 5:25 pm

so how and why would all 47 f1 offspring be homoglomus? and how can it be proved?
star21
Garter
Garter
 
Posts: 13
Joined: Wed May 04, 2005 10:07 pm

Postby MrMistery » Fri May 13, 2005 7:27 pm

It is proved theoretically:From B and b nothing else will ever result than Bb
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
User avatar
MrMistery
Inland Taipan
Inland Taipan
 
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)


Postby MrMistery » Fri May 13, 2005 7:33 pm

Be warned though, in a backcross that procent of 50% is strictly theoretical: in reality you will get procents close to that, but not quite... Also, if your population is not pancmictical than you can kiss your whole experiment bye-bye
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
User avatar
MrMistery
Inland Taipan
Inland Taipan
 
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)

Postby star21 » Fri May 13, 2005 8:32 pm

but why this is what i cannt get my head around, i know it is, but how can i explane this
star21
Garter
Garter
 
Posts: 13
Joined: Wed May 04, 2005 10:07 pm

Postby MrMistery » Sat May 14, 2005 6:50 pm

A gamet is a haploid cell. If one gamet has the B gene and one gamet has the b gene than the resulting diploid organism will be Bb. If all your males were BB and your females were bb then all the male gamets will be B and the female gamets will be b. Since a male gamet can olny fuse with a female gamet and vice-versa then nothing else can resul but Bb
Get it?
Regards,
Andrew
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
User avatar
MrMistery
Inland Taipan
Inland Taipan
 
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)

Postby star21 » Sat May 14, 2005 8:34 pm

yes FINALLY i do, bet ur glad u answer my question. any way thank you for your help
star21
Garter
Garter
 
Posts: 13
Joined: Wed May 04, 2005 10:07 pm

Postby MrMistery » Sun May 15, 2005 6:02 pm

Welcome. That's what i don't have a social life for :) :)
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
User avatar
MrMistery
Inland Taipan
Inland Taipan
 
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)

Postby star21 » Mon May 16, 2005 10:14 pm

well what about just one more question then? :D
what evidence is there that the parents of the 47 offspring where pure breeding for these characterustics. (offspring all had red eyes and grey bodie)?
star21
Garter
Garter
 
Posts: 13
Joined: Wed May 04, 2005 10:07 pm

Postby MrMistery » Tue May 17, 2005 6:59 pm

Ok, so here you have to think in reverse. I am going to explain for only one set of genes, it is the same for any number of pairs. If you have only one parent individual heterozygotus Bb and all the other homozygotus BB than the recessive gene will not manifest in F1(all individuals in f1 will have dominant carachteristics). But if at least two of your organisms that are of opposite sexes have the b recessive gene it may show up in F1(if two heterozygotus organisms breed you will get 25% BB, 50% Bb and 25% bb. This bb-25% of the total possible offspring-are the organisms showing recessive traits because the reccesive gene can manifest).
So, you should give the following answer: "though it is not sure, the most probabile cause of the traits of the individuals in f1 is that all the parents where homozygotus dominant"
If your teacher or professor says comments anything, just show him my answer. I am sure he will agree
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
User avatar
MrMistery
Inland Taipan
Inland Taipan
 
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)

Postby star21 » Wed May 18, 2005 12:12 am

:D thanks for all the help
star21
Garter
Garter
 
Posts: 13
Joined: Wed May 04, 2005 10:07 pm

Previous

Return to Cell Biology

Who is online

Users browsing this forum: No registered users and 0 guests

cron