Question

2) How would you explain gene expression? How is it that a particular genotype is actually expressed as a phenotype? I am looking for details here, including an explanation of the molecular mechanisms involved.

Answer 1

The pyrimidine bases ( cytosine and thymine in DNA and uracil in RNA ) and the purine bases ( adenine and guanine ) along with the deoxyribose and ribose sugar and phosphate group unite to form nucleotide constitute genes.

Genes mainly vary due to different arrangement of those nitrogenous bases.

According to Central dogma during transcription complementary bases are transcribed into RNA from DNA and during translation the arrangement of bases upon specific m-RNA in triplet manner constitutes codon that binds with t-RNA having anticodons and carrying amino acids. These amino acids unite to form proteins. This is known as gene expression as per the coding sequence of m-RNA that is transcribed by a specific DNA sequence or a specific gene.

Hence a specific gene represents a specific enzyme. But expression of a certain phenotype needs several types of enzyme.

That means many genes are need to be expressed for a phenotype. Genotype means the particular genes that are responsible for a phenotype to be expressed. In this way the genes that forms the particular enzymes that are responsible for a particular trait are called genotype of a particular trait and need to be expressed for that phenotype.