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selective breeding question

hi,

im doing a paper from jan11 and im confused on this 2 mark question...

'suggest two undesirable consequences of selective breeding in chickens' (2)

the mark scheme says:
growth too rapid ;
increased susceptibility to, disease / named abnormality ;
inbreeding ;
reduces gene pool / genetic variation / genetic diversity ;

but i still dont get it.

thanks in advance for any help :smile:
Reply 1
Avatar for Dynamo123
Dynamo123
7
Which portion you don't get?
Selective breeding means some important genes are going to vanish. Suppose you put a white eyed and a red eyed male and a white eyed and a red eyed female Drosophila in a container. After fifteen generations, there are red eyed individuals in abundance, but the white eyed are less. This is because both the red eyed female and the white eyed female prefer to mate with the red eyed male. And the white eyed male, left alone, ultimately produces little progeny. So alleles for white eyed trait ultimately become less, and the allele tends to get fixed.(If all individuals in population are homozygous for a trait, its alleles become fixed and no variability is produced.)

It's confusing, yea, but I think It might be helpful.
Original post by Dynamo123
Which portion you don't get?
Selective breeding means some important genes are going to vanish. Suppose you put a white eyed and a red eyed male and a white eyed and a red eyed female Drosophila in a container. After fifteen generations, there are red eyed individuals in abundance, but the white eyed are less. This is because both the red eyed female and the white eyed female prefer to mate with the red eyed male. And the white eyed male, left alone, ultimately produces little progeny. So alleles for white eyed trait ultimately become less, and the allele tends to get fixed.(If all individuals in population are homozygous for a trait, its alleles become fixed and no variability is produced.)

It's confusing, yea, but I think It might be helpful.



first thanks for the response

secondly how does selective breeding increase the susceptibility to disease then?

thanks again
Reply 3
Avatar for johnny-marr
johnny-marr
Inbreeding reduces the allele frequency, so there is less genetic diversity. Therefore if the animal gets a disease and they all have similar or the same alleles it becomes much more difficult to fight the disease and adapt against it, so they become more susceptible because they are similar. It allows diseases to not have to evolve or mutate to infect the chickens.
Reply 4
Avatar for Dynamo123
Dynamo123
7
Original post by ThePremierLeague
first thanks for the response

secondly how does selective breeding increase the susceptibility to disease then?

thanks again


I guess your second question was answered pretty well.
Just another example to add up on:
Suppose that chicken cholera is caused by a single gene malfunctioning. If the alleles for that gene are fixed in the population's gene pool, then all individuals will be equally likely to catch chicken cholera, and pass into the void. :P :colone:
Original post by johnny-marr
Inbreeding reduces the allele frequency, so there is less genetic diversity. Therefore if the animal gets a disease and they all have similar or the same alleles it becomes much more difficult to fight the disease and adapt against it, so they become more susceptible because they are similar. It allows diseases to not have to evolve or mutate to infect the chickens.


thanks bro
Original post by Dynamo123
I guess your second question was answered pretty well.
Just another example to add up on:
Suppose that chicken cholera is caused by a single gene malfunctioning. If the alleles for that gene are fixed in the population's gene pool, then all individuals will be equally likely to catch chicken cholera, and pass into the void. :P :colone:


thanks bro

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