Learning Intention: Students will understand the genetic code as a degenerate triplet code and the steps in gene expression including transcription, RNA processing in eukaryotic cells and translation. Students will also understand gene structure and regulation, especially start/stop, promoter regions, exons/introns and the lac operon.
Transcription – the process by which the DNA code is transcribed into messenger RNA in the nucleus of a cell. (DNA to mRNA)
RNA processing – the process by which introns are removed and the exons are spliced together, leaving a single-stranded mRNA molecule which travels through the nuclear pores into the cytoplasm.
Translation – the process by which the mRNA code is converted to a protein code by ribosomes adding amino acids that are attached to an anticodon that pairs with codons on the mRNA strand.
Gene structure and regulation
• the functional distinction between structural genes and regulatory genes
• the structure of genes in eukaryotic cells including stop and start instructions, promoter regions, exons and introns
• use of the lac operon as a simple prokaryotic model that illustrates the switching off and on of genes by proteins (transcriptional factors) expressed by regulatory genes.
Non-coding DNA explained
DNA transcription promoter
Gene expression and order of the operon
Lac operon from Virtual Cell
Learning Intention: To understand nucleic acids as information molecules that encode instructions for the synthesis of proteins in cells and the processes of transcription and translation in cells. Students will also understand protein functional diversity and the nature of the proteome as well as the functional importance of the four hierarchal levels of protein structure. They will perform experiments that demonstrate the effect of temperature and pH on enzymes.
- Catalase is an enzyme found in liver extract that breaks down hydrogen peroxide (H2O2) into water and oxygen.
- Hydrogen peroxide is a toxic product of digestion that needs to be eliminated from the body. Water and oxygen are the safe products of hydrogen peroxide breakdown.
- Primary structure of protein – order of amino acids
- Secondary structure – alpha helix, beta pleated sheets or random coils
- Tertiary structure – folding of the polypeptide chain due to disulphide bridges and other attractions or repulsions between molecules.
- Quarternary structure – two or more polypeptide chains folded together to form a complex protein.
Biomacromolecules – Nucleic acids and proteins (Part A) from GTAC
Biomolecules – Nucleic acids and proteins (Part B) from GTAC
Nucleic acids (DNA and RNA) are the next group of macromolecules that we are looking at. Nucleic acids are made up of monomer units that consist of a phosphate group, a sugar unit and a nitrogenous base. The nitrogenous bases in DNA are Thymine (T), Adenine (A), Guanine(G) and Cytosine (C). In RNA, the Thymine (T) is replaced by Uracil (U). Thymine (or Uracil in RNA) always pairs with Adenine (2 hydrogen bonds) and Guanine always pairs with Cytosine (3 hydrogen bonds).