The traits we have studied so far fall into a few easily distinguishable classes that we use to predict the genotypes of individuals (McClean, 1997). Mendel worked with features that were all discrete, for example these features were yellow or green, round or wrinkled, etc. A phenotype can be predicted from the known genotype and various alleles result in distinctly discernible phenotypes (McClean, 1997). These types of phenotypes are called discontinuous traits. However, many traits do not fit into distinct categories since there is a continuous distribution of phenotypes. The distribution is similar to the bell-shaped curve for a normal distribution. These types of phenotypes are known as continuous traits and are studied differently from discontinuous traits. Examples of these traits are learning ability in humans, weight gain in animals or ear length in corn. These traits are regulated by multiple genes, each segregated according to Mendel's laws, and can also be influenced by the environment at varying levels (McClean, 1997). Since continuous characters are frequently calculated and given a quantitative value, they are commonly called quantitative. features. Thus, quantitative genetics is known as the field of study of the inheritance of coherently calculated traits and their mechanisms (McClean, 1997). Today, famine is rare because quantitative trait management has led to a significant increase in crop yield over the past 80 years. years. Yield is the most essential and complex trait for crop genetic improvement because it reflects the interaction of the environment with all the advanced procedures that occur throughout the life process (2). This was the most profitable feature of genetics until not long ago. This was... middle of article...... Mapping and analysis of candidate genes for plant architectural traits using rice whole genome re-sequencing http:// www. ncbi.nlm.nih.gov/pmc/articles/PMC3935628/(4) Mutations and quantitative genetic variation: lessons from Drosophila http://rstb.royalsocietypublishing.org/content/365/1544/1229.long (5) Variation quantitative genetics of odor-guided behavior in a natural population of Drosophila rnelanogaster http://www.genetics.org/content/144/2/727.full.pdf(6) Wilhelm Johannsen's genotype-phenotype distinction http:/ /embryo.asu.edu/pages/wilhelm-johannsens-genotype-phenotype-distinction (7) An analysis of Wilhelm Johannsen's genetic term "genotype" 1909-26 http://onlinelibrary.wiley.com/doi/10.1111/j .1601-5223.1975.tb01456.x/pdf (8) Griffiths AJF, Miller JH, Suzuki DT et al. An introduction to genetic analysis. 7th edition New York: WH Freeman; 2000.