Chapter 1 Summary

The topics covered in this chapter can be summarized as follows:

• Mendel demonstrated that heredity involved discrete, heritable factors that affected specific traits.
• A gene can be defined operationally as a unit of inheritance.
• Homologous chromosomes contain the same series of genes along their length, but not necessarily the same alleles. Sister chromatids initially contain the same alleles.
• Homologous chromosomes pair (synapse) with each other during meiosis, but not mitosis.
• A diploid organism can have up to two different alleles at a single locus. The alleles segregate equally between gametes during meiosis.
• Phenotype depends on the alleles that are present, their dominance relationships, and sometimes interactions with the environment and other factors.
• Classical geneticists make use of true breeding lines, monohybrid crosses, Punnett squares, test crosses, and reciprocal crosses.