Gene variants that arise by mutation and exist at the same relative locations on homologous chromosomes are called alleles. Diploid organisms produce haploid gametes, which contain one copy of each homologous chromosome that unite at fertilization to create a diploid zygote.įor cases in which a single gene controls a single characteristic, a diploid organism has two genetic copies that may or may not encode the same version of that characteristic. The same is true for many other plants and for virtually all animals. In other words, peas are diploid organisms in that they have two copies of each chromosome. Each pair of homologous chromosomes has the same linear order of genes. The genetic makeup of peas consists of two similar, or homologous, copies of each chromosome, one from each parent. Physical characteristics are expressed through genes carried on chromosomes. Identify non-Mendelian inheritance patterns such as incomplete dominance, codominance, recessive lethals, multiple alleles, and sex linkage.Explain the purpose and methods of a test cross.Develop a Punnett square to calculate the expected proportions of genotypes and phenotypes in a monohybrid cross.Explain the relationship between genotypes and phenotypes in dominant and recessive gene systems.By the end of this section, you will be able to do the following:

Rare dominant traits