• Question: What is an Allele?

    Asked by Paka Maka the 1st (Adira) to Yinka, Stéphane, Gemma on 13 Mar 2018.
    • Photo: Stéphane Berneau

      Stéphane Berneau answered on 13 Mar 2018:

      An allele is a copy of a gene that you have inherited one from your mum and one from your father. Alleles are important for multiples characteristics such as eye colours and disease.
      For example, if the disease is allele recessive, it means that you need the allele for it on both genes (paternal and maternal) to express the disease in your cells. Parents are a carrier of the disease allele but do not have to be expressing the disease.
      If the disease is dominant, only one allele is necessary for you to express it. It also means that one of the parents has the disease.

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    • Photo: Gemma Chandratillake

      Gemma Chandratillake answered on 13 Mar 2018:

      Think of an allele as the “flavour” of the gene, so just as you can have chocolate, strawberry, or vanilla ice cream, you can have different versions of genes. This is why we are different from each other, because we have different versions of our genes. We have two copies of each gene, one from our mum and one from our dad. If both the copies are the same, we say that we are homozygous for that allele. If the two copies of the gene are different, we say that we are heterozygous for each allele. You can think of the human population as a pool of alleles for each gene – all the different versions of that gene that are available. Each of us has two of these alleles for each gene, which may be the same or may be different, depending on what we inherited from our parents. Different alleles can be common or rare in the population depending on chance and/or selection.
      An example, do you know what your blood group is? Mine is B. Your blood group is determined by the combination of alleles that you have for the ABO gene. The alleles for blood groups A and B are dominant over the allele for blood group O. My mum is B, my dad is O, and my sister is O. So, my Dad’s alleles have to be O and O, because O is recessive to the other types. My sister has to be O and O too for the same reason, which means that my mum must have an O allele as she passed one on to my sister. So my mum’s alleles are B and O, giving her blood group B. My alleles must be B from my mum, giving me blood group B, and O from my Dad (because that’s all I could’ve inherited from him. http://www.biology.arizona.edu/human_bio/ABO_Crosses.html

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