Year+12+Genetics

The term //genetic code// refers in this context to the sequence of bases on the DNA molecule. DNA replication comprises unwinding the DNA molecule, breaking the bonds between the strands, replication, and repackaging. Candidates should understand the roles of key enzymes in this process, including RNA and DNA polymerases, DNA ligase and DNA helicase. The significance of DNA replication to gene expression is that it is a semi-conservative process that maintains and transmits the genetic code with a high level of accuracy. The role of DNA in determining protein structure: students should be aware of the significance of codons and anticodons, and of the redundant nature of the code. The term //phenotype// includes not only visible features, but also physiological and behavioural characteristics that are determined by the outcome of interactions between the genotype and the organism's environment. Statement of genotype and phenotype frequencies may be expressed as a ratio, fraction or percentage. Control of metabolic pathways by gene expression in eukaryotes includes enhancers and transcription factors. Candidates should understand the role of control elements, including the promoter region, enhancer region, the transcription factors (proteins) that must bind to both regions before transcription can occur, and the terminator region. Candidates should also understand the role of operons in control of gene expression in prokaryotes.
 * **Achievement Standard Number 90715** ||
 * **Title** || Describe the role of DNA in relation to gene expression ||
 * **Version:**2 || **Number of Credits:** 4 ||
 * **Special notes** || For the structure of DNA, the molecular components of DNA are the nucleotides (deoxyribose, a phosphate group, and a base, where the bases are Adenine, Thymine, Guanine, Cytosine).

website : [] for DNA replication ||