BIO.7.B
The student is expected to describe the significance of gene expression and explain the process of protein synthesis using models of DNA and ribonucleic acid (RNA);
Knowledge and Skills Statement
Science concepts--mechanisms of genetics. The student knows the role of nucleic acid in gene expression.
Further Explanation
It may be helpful to provide some concrete examples of gene expression to students while discussing the process of protein synthesis. It is important to recognize that protein synthesis is the mechanism through which gene expression occurs.
One example to consider is lactose intolerance. In humans who can digest dairy, there is a particular gene (the LCT gene) that is activated whenever lactose is introduced to the body. When the LCT gene is activated, the cell begins to synthesize the enzyme lactase, which helps digest lactose. In people who are lactose intolerant, the expression of lactase has greatly decreased, the enzyme synthesized is abnormally short, or it is otherwise ineffective. This is why people who are lactose intolerant have digestive difficulty after consuming dairy.
Another example is that sex differentiation in turtles is dependent on the environmental temperature of the nest. The genes which produce male characteristics are activated when eggs are exposed to lower temperatures. The genes which produce female characteristics are activated when eggs are exposed to warmer temperatures.
Supporting Information
Research
Chen, Shanyi, Ting Ye , Lu Hao, Hui Chen, Shaojie Wang, Zaifeng Fan, Liyun Guo, Tao Zhou "Infection of Apple by Apple Stem Grooving Virus Leads to Extensive Alterations in Gene Expression Patterns But No Disease Symptoms." PLoS ONE 9, no. 4 (April 2014):e95239. https://doi.org/10.1371/journal.pone.0095239
Summary: To understand the molecular basis of viral diseases, transcriptome profiling has been widely used to correlate host gene expression change patterns with disease symptoms during viral infection in many plant hosts. We used infection of apple by Apple stem grooving virus (ASGV), which produces no disease symptoms, to assess the significance of host gene expression changes in disease development. We specifically asked the question of whether such asymptomatic infection is attributed to limited changes in host gene expression.
Research
Brakmann, Susanne. "A Ribosome in Action: The Manufacture of Proteins by Ribosomes Involves Complex Interactions of Diverse Nucleic Acid and Protein Ligands. Single-molecule studies allow us, for the first time, to follow the synthesis of full-length proteins in real-time." Nature 464, no. 7291 (April 2010): 987+.
Summary: Protein synthesis involves a complex interplay of various cellular components. Ribosomes are the cell's protein-production factories, and interact with messenger RNA (the template), amino-acylated transfer RNAs (which act as adaptors between mRNA and amino-acid residues) and diverse co-factors (for the initiation of synthesis, elongation of the nascent chain and release of the mature polypeptide). Uemura et al. report the use of an extremely sensitive single-molecule detection technique to observe this process at unprecedented resolution: the stepwise synthesis of a single protein.
Research
Golding, Ido, and Edward C Cox. "Protein Synthesis Molecule by Molecule." Genome Biology 7, no. 221 (June 2006).
https://doi.org/10.1186/gb-2006-7-6-221
Summary: Since the earliest days of molecular biology it has been known that even a seemingly uniform culture of bacteria is made up of cells very different from each other in terms of their levels of a given protein. This individuality has now finally been quantified at single-molecule resolution, as reported in two recent papers.