|MadSci Network: Genetics|
Dear Cara, I am not too sure how the Americam education system works so I'm not too sure how old your brother is. I think that his teachers are trying to get him to demonstrate a knowledge of genetic crosses, like Mendel's peas. First, I am assuming that these'zoots' are imaginary - I've never heard of one. We are dealing with three genes - one for colour, one for intelligence and one for height. The different forms of the genes are called alleles so there are two alleles for each gene e.g. sort and shorter for the height gene. You have two test subjects. Do you know what the terms homzygous and heterozygous mean? If an organism is homozygouss the two alleles it has for the gene are the same. e.g. two alleles for brown. To be heterozygous is to have two different alleles -e.g. one for white and one for brown at the colour gene. O.k. Assuming that the test subjects are homozygous, when they breed together, they can only pass on one of the alleles they have in their egg or sperm. This means that zoot one can only pass on alleles for being brown, short and moronic and zoot two can only pass on alleles for being white, shorter and intelligent. The offspring of this mating are therefore going to be heterozygous at each of the three genes - they will have a mixture. This is where the question about dominance comes in. Will the offspring be short or shorter, white or brown, intelligent or moronic. Whatever the offspring look like will answer whether brown or white is dominant - if it is brown then the brwon allele is dominant and vice versa. If it is intelligent then the allele for intelligence is dominant or vice versa if it is moronic and if it is short then the allele for being short is dominant or vice versa if it is shorter. Now, I'll give a little extra here and you judge for yourself if this is for your brother's age or not. I think the reason why they mention some zoots are shiny and tan is because they may be wanting your brother to realise that these are mutants with different versions of the height and colour alleles. A height allele for tall and a colour allele for tan. I hope this has answered your question. Check out chi-squares, genetic crossing and mendel's peas for more info - do a web search if there is nothing in your school text book. Best wishes, Yvonne
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