Phenotypes are the observed physical structure. Genotype is the genetic composition. An Allele is one version of a gene. Some genes are neither dominant nor recessive and the heterozygote is a third phenotype. So all possible combinations of round or wrinkled and yellow or green seeds were observed in predictable ratios.
Males have an X and a Y, females have two X's.
When two genes are located on the same chromosome, they are usually transmitted together, and are thus Linked . At the start of Meiosis, Synapsis occurs and homologous chromosomes form pairs with their long axes parallel and the chromosomes have duplicated to form two chromatids. Chromosome breakage or some other event allow the broken chromatids to rejoin in a mixed manner. There can be multiple crossovers along a single chromosome. Interference can either increase or decrease the probability of correlated crossovers.