Key words genetics

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      • The genetic makeup of an organism
        • It describes the organism in terms of the alleles it contains, usually in the context of a particular characteristic
          • An organism with two identical alleles for a gene is homozygous
          • An organism with two different alleles for the same gene are heterozygotes
      • Refers to the characteristics that are expressed in an organism, those features which can be observed
        • These are determined by genotype and environment
      • An allele is said to be dominant if it is always expressed in the phenotype
        • This is even if a different allele for the same gene is present in the genotype
      • An allele is said to be recessive if it is only expressed in the phenotype in the presence of another identical allele
      • Two alleles for the same gene are said to be codominant if they are both expressed in the phenotype of a heterozygote
      • Linkage refers to two or more genes that are located on the same chromosome
        • The linked alleles of these genes are normally inherited together because they do not segregate  independently at meiosis, unless chiasmata have been formed between them
      • A characteristic is sexed linked if the gene that codes for it is found on one of the sex chromosomes


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