An allele is an alternate form of a gene. Genotype refers to the physical expression or manifestation of the gene. In a test cross, the homozygous dominant must always be used as one of the parents. In chickens it is the female that determines the sex of the offspring. Expressivity refers to the degree to which the phenotype is visible or manifested.
Chromosomes are long stretches of amino acids.
Polytene chromosomes are generated by many rounds of DNA replication without cytokinesis. The S phase of the cell cycle is when the cell accumulates carbohydrates to prepare for mitosis. Mitosis results in two identical daughter cells whereas meiosis results in four identical, although haploid, cells. Loci are positions on the chromosomes where genes occur. The number of protons in an atom equals the number of electrons.