Biology Answers

QUESTION NINE: BREEDINGA chicken farmer discovers a chicken which has four legs.a) Explain what must have happened for the chicken to be born withfour legsThe farmer raises chickens to sell to a fried chicken restaurant. He getspaid for each leg he supplies.b) Discuss what he would have to do to get a pure breeding strain offour legged chickens. Assume the allele for four legs is dominant(L) and show punnett squares with your answer. A completeanswer would mention any possible negative side effects as well)ANSWER NINE: BREEDINGa) For Achievement your answer should have ONE correct statement.There was a mutation in the DNA of the chicken.The chicken must have been born with a mutation in its genetic codeFor Merit your answer should have ONE correct explanation. EitherA mutation (a change to the base sequence of a gene along the DNA) or a change inthe genetic code must have occurred. ORFor the chicken to have been born with this mutation it must have occurred in the zygote(first fertilised cell) or in the sex cells of one of its parents.b) For Achievement your answer should have ONE correct statement.For Pure breeding this feature a chicken would need to be LLThe original mutant chicken genotype is unknown, must be LL or Ll (probably Ll)The mutant chicken would need to be bred with other normal chickens and its offspringbred from as well.For Merit your answer should have a partial explanation. (i.e. does not explain howto separate heterozygous from homozygous dominant chickens AND does notexplain possible negative side effects)Mate the chicken with lots of normal chicken (genotype ll) to produce heterozygous fourleggedchicken. These are the F1 generation.Mate different combinations of F1 generation four-legged chicken in order to producemore four-legged chicken. These are the F2 generation. Do not keep any non-fourleggedchicken as they do not carry the mutant allele.Mate different combinations of F2 generation four-legged chicken to produce more fourleggedchickensFor Excellence you should have a full explanation, including side effects.Mate the chicken with lots of normal chicken (genotype ll) to produce heterozygous fourleggedchicken. These are the F1 generation.Mate different combinations of F1 generation four-legged chicken in order to producemore four-legged chicken. These are the F2 generation. Do not keep any non-fourleggedchicken as they do not carry the mutant allele.Then Either:Mate different combinations of F2 generation four-legged chicken. (Some will beheterozygous, others homozygous dominant)If the offspring from one chicken in any pairing are non-four-legged, remove that parentfrom the breeding program. (Must be Ll)If the offspring are four-legged in all cases for one chicken’s offspring, you can beconfident that it is homozygous dominant for four-legs. Keep all these types of chicken forfurther breeding. (Should be LL – pure breeding for 4 legs)ORCarry out test crosses of the F2 generation by breeding them with normal chickens. Anythat have normal offspring must be heterozygous and should be removed from thebreeding program. Any that have no normal offspring are probably homozygous dominant.Possible negative side effects are that when you bred to reinforce a (desired) feature,you may also reinforce an undesired feature. I.e. if the original chicken had someweakness (e.g. a bad heart) all the offspring could end up with this weakness as well)