Understanding the Functions of Proteins and DNA Ingrain Waldron, Biology Department, University of Pennsylvania, 2012 These key concepts and activities are suggested as part of an introductory unit on biological molecules (or as an introduction too unit on molecular biology). The overarching goal is to help students understand that proteins and DNA are not Just abstract concepts in biology textbooks but rather crucial components of our bodies that affect familiar functions and characteristics.
Key Concepts: Proteins are responsible for many important aspects of cell structure and unction. Differences in the structure and function of proteins result in differences in the characteristics of biological organisms. Teaching Approaches: 1. Brainstorming session using the probe “What are proteins? Why are proteins important? ” 2. Show Youth video “Protein Functions in the Body” http://www. Youth. Mom/watch? V=T500B5yTy58 omit hormone section which has inaccuracies ask students to identify 5 functions of proteins 3. Hands-on activity: Enzymes Help Us Digest Food (available at http:// serendipity. Barnyard. Deed/sic_Deed/Waldron/#enzymes) Experiments using the enzyme acetates and discussion questions help students to learn about enzyme function, enzyme specificity, and the molecular basis of lactose intolerance.
Students also learn about the scientific method by interpreting evidence to test hypotheses and designing the second and third experiments to answer specific scientific questions about lactate. 4. Review protein functions and reinforce the idea that, if a protein is missing or defective, this has observable effects on our bodies: Protein Function Examples Effect if This Protein Missing or Defective* Enzyme Lactate (breaks down lactose)Lactose intolerance (difficulty digesting milk)
Enzyme for synthesizing melanin (pigment that gives our skin and hair color) Albinism (very pale skin and hair) Transport Hemoglobin (protein in red blood cells which transports oxygen in the blood) Sickle cell anemia Clotting Clotting proteins in blood Hemophilia (excessive bleeding) *Teacher intimation on these conditions is provided, beginning on the next page. DNA contains genes which provide the information necessary to make proteins. Ђ Different versions of the same gene result in different versions or amounts of a protein, and the differences in the protein result in different characteristics illustrated in the table above). 1. Discussion of probe question “Why do some people have lactose intolerance, albinism, sickle cell anemia, or hemophilia, and other people don’t? ” 2. Show “What is a gene? ” available at http://learn. Genetics. Utah. Deed/content/begin/ tour/ – illustrates both Key Concepts for this section 3. Revisit probe question.
Teacher Information about Conditions Resulting from Missing or Defective Proteins Lactose Intolerance The alleles for the gene for lactate differ in the nucleotide sequence in the regulatory DNA; this difference influences the rate of transcription of the coding DNA and thus influences the rate of production of the protein, lactate. Lactate persistence alleles result in substantial production of lactate throughout life. The lactate omnipresence allele results in substantial production of lactate by infants, but very low levels of lactate in adults, resulting in lactose intolerance.
In the most common form of albinism, the lack of the pigment melanin affects not only skin and hair color, but also the appearance and function of the eyes. Further information about the various forms of albinism, as well as a great deal of information on other aspects of human genetics, is available from MIM, Online Madeline Inheritance in Man (www. Incubi. Ml. NIH. Gob/MIM/; search for 223100 (lactose intolerance), 606952 (albinism), 603903 (sickle cell anemia), or 306700 or 306900 (hemophilia)). Students may ask about the distinction between inherited albinism and vitality.
Albinism is the inability of the body’s cells to produce melanin and affects the whole body. Vitality is a patterned loss of melanin pigment resulting from the destruction of melancholy’s; the hypertrophied areas appear on the skin of a person with normal pigmentation. (Additional information from the National Vitality Foundation is available at www. Nevi. Org. ) (continued) Sickle cell anemia Sickle cell hemoglobin is less soluble in the watery costly of the red blood cells than normal hemoglobin, particularly when oxygen concentrations are low.
Thus, sickle ell hemoglobin tends to form long stacks or rods of hemoglobin molecules, which results in the sickles shape of some red blood cells in a person who is homozygous for the sickle cell allele and consequently has sickle cell anemia. The sickles red blood cells tend to clog the tiny capillaries, blocking the circulation in different parts of the body. Also, the sickles red blood cells do not survive as long as normal red blood cells, contributing to a tendency to anemia. Resulting symptoms include pain, physical weakness, impaired mental functioning, and damage to organs such as the heart and kidneys.
Protein 0 Phenotype Normal hemoglobin dissolves in the costly of red blood cells 0 Disk-shaped red blood cells can squeeze through the capillaries 0 normal health Sickle cell hemoglobin can clump in rods in red blood cells 0 Some red blood cells are sickle-shaped – > clogged capillaries and fragile red blood cells 0 pain, damage to body organs, anemia In a person who is heterozygous for the sickle cell and normal hemoglobin alleles, each red blood cell has both sickle cell and normal hemoglobin.
The amount of normal hemoglobin is sufficient to prevent the symptoms of sickle cell anemia in almost all cases. The sickle cell hemoglobin in each red blood cell decreases the severity of malaria in heterozygous individuals because the malaria parasite doesn’t grow as well in red blood cells containing sickle cell hemoglobin. Additional information can be found in “Sickle cell anemia”, available at www. Monoclinic. Com/health/sickle-cell-anemia/DISCUSS A video, “Sickle cell anemia” is available at http://www. Him. Rig/bioinformatics/DNA/Dana_sickles. HTML Hemophilia An injury to a blood vessel triggers the activation of a series of blood-clotting proteins which culminates in the activation of thrombi which converts forefinger to fibrin which forms a clot. When one of the blood-clotting proteins is defective, it takes an abnormally long time tort a b clot to tort, resulting in excessive bleeding tater injury or surgery. In severe cases, a person may experience spontaneous bleeding. This condition is called hemophilia.
Hemophilia is due to alleles that code for defective clotting proteins, most commonly alleles of one of two genes on the X chromosome. Since a male has only one X chromosome in each cell, if his X chromosome has an allele that codes for defective looting protein, he will not be able to make blood clots properly and he will have hemophilia. In contrast, a female has two X chromosomes, so she generally only has hemophilia if she is homozygous for a recessive allele for a defective clotting protein.
In most heterozygous women, approximately half of her liver cells have the X chromosome with the normal allele active (due to random inactivation of one X chromosome in each cell), and these cells are able to make enough blood clotting protein to prevent hemophilia. However, in some heterozygous women random inactivation of one X chromosome in each cell has resulted in less than half the cells in her liver having the X chromosome with the allele for the normal clotting protein and these women may have mild hemophilia (e. . With heavy prolonged menstrual bleeding and frequent nosebleeds). Additional information can be found in “Hemophilia”, available at http:// gar. Ml. NIH. Gob/condition/hemophilia Additional Resource for Teaching about Macromolecules: Who took Sorrel’s pod? An Organic Compound Mystery (a hands-on activity available at http://serendipity. Barnyard. Deed/sic_Deed/Waldron/#organic ) In this activity, students earn how to test for triglycerides, glucose, starch, and protein and then use these tests to solve a mystery.
The activity reinforces students understanding of the biological functions and food sources of these different types of organic compounds. Additional Resources for Teaching Molecular Biology: Multiple activities for teaching about DNA structure, replication and function, transcription and translation, and the molecular biology of mutations are suggested in “Molecular Biology: Major Concepts and Learning Activities” (available at http:// serendipity. Barnyard. Deed/exchange/biostatistics/Million).