CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF STUDY
Over the years, right from the second half of the 20th century, genetics progressively became an essential field of biology also feeding controversial ethical, social and economical debates. The multiplicity and availability of products and applications of genetic technology (GMOs, DNA fingerprinting, screening of genetic diseases, gene therapy, cloning, … ) are more and more daily present, requiring us a high level of scientific literacy and understanding of these issues for a citizenship control (Dawson & Schibeci, 2003; Marbach-Ad, 2001).
According to Banet & Ayuso, (2003) stated that genetics is also one of the most difficult subjects in the biology curricula at the secondary school. The term “gene” was introduced by Wilhelm L. Johannsen in 1909. This central concept in genetics was initially defined as an entity of calculations to account for the transmission of hereditary traits. It became a material entity firstly as a part of chromosome (Morgan, 2001) and then, with the development of molecular biology, as a segment of DNA. More recently, three types of genes were defined related to their functions: genes coding for proteins, genes specifying the untranslated RNA (tRNA, RNAs … ) and the regulatory genes. The more recent conceptions of gene have never totally replaced earlier conceptions: Multiple scientific conceptions of the gene are coexisting (Morange, 2004). Several authors tried to categorize them. Griffiths distinguished two different conceptions of the gene: The molecular gene is “the molecular process underlying the capacity to express a particular polypeptide product”, and the evolutionary gene is “a theoretical entity with a role in a particular, atomistic approach to the selection of phenotypic traits” (Griffiths & Neumann, 2009). Later, Griffiths and Stotz outlined three conceptions of the gene: instrumental, nominal, and postgenomic:
“The instrumental gene has a critical role in the construction and interpretation of experiments in which the relationship between genotype and phenotype is explored. The nominal gene is a critical practical tool, allowing stable communication between bioscientists in a wide range of fields grounded in welldefined sequences of nucleotides, but this concept does not embody major theoretical insights into genome structure or function. The post-genomic gene embodies the continuing project of understanding how genome structure supports genome function, but with a deflationary picture of the gene as a structural unit”. (Griffiths & Stotz, 2006).