BCH190 The Way We Work With Life
Study Guide Quiz 06, 2006
1. In the 1860s Gregor Mendel discovered “factors” that determined inheritance of traits in plants (notice how many great discoveries appear first from work on plants) and by 1906 Thomas Hunt Morgan showed that ‘genes’ are the “factors” that Mendel had discovered, and that genes are located on chromosomes. Then in 1944 Oswald Avery showed that genes are made of DNA! (We have come a long way). We now know all the genes in
2. Life took about 4 billion years to reach its present level of complexity. To maintain it, life must always come from life, replicating its DNA and passing that information, however slightly changed, from generation to generation. This inevitable conclusion comes from our modern understanding of the key role played by
3. Former President Jimmy Carter has said that ‘Biotechnology is not a threat…starvation is.’ Vitamin A deficiencies are responsible for a million lives a year globally and many of those are in developing countries where the main staple is rice. Dr. Ingo Potykus of Switzerland genetically modified rice to accumulate high levels of beta carotene the natural precursor for vitamin A. Some have argued that it would be unethical to deny this population of such a useful tool to alleviate suffering. This variety is known as:
4. While it has not yet been done for all organisms on earth, based on what we now know, it is possible to clone any gene from almost any living organism, transfer that gene into another unrelated organism, and make the same protein coded for by that gene. This means that the genetic code is a universal language for life on this planet.
5. Plants that have been genetically modified for crop improvement, including corn, canola, cotton, and soybean in the US, have been widely adopted by farmers to reduce input costs and pesticides. The products from these plants
6. The first commercially available genetically engineered plant was released in 1992. It was
7. Gene constructs can be readily made in the laboratory by fusing together DNA segments from different sources. If done correctly, these cloned constructs can be delivered into plants where there will be stably integrated into the plant’s DNA and expressed to confer new and useful traits. Gene constructs can be introduced into plants by
8. The segments of DNA that we call genes usually code for proteins. The region of a strand of DNA, which is ‘upstream’ of the coding sequence either turns on or off the expression of a particular gene. When we say a gene is ‘on’ we mean that it is making mRNA and that protein is translated from that mRNA. In humans and in other animals, there must be eye specific genes, liver specific genes, and genes that are expressed in all cells. Similarly in plants there must be flower specific genes, leaf specific genes, root specific genes and so on. These genes make the proteins that are specific for each function in each tissue. These ‘upstream’ sequences that regulate cell and tissue specific expression are called
9. Agricultural Biotechnology:
10. It is now possible to make gene constructs in the laboratory by fusing together DNA segments from different sources. If done properly, these cloned constructs can be expressed in plants to confer new and useful traits. For example, genes that encode proteins from a bacteria can be moved into plants to make them resistant to pests without using pesticides. This process of plant improvement has been
11. It is also interesting that because all life on this planet uses information in the form of either DNA, RNA or both, and that the same bases are used, and that the genetic code is almost always the same using three of those bases to code for one of twenty amino acids…because now genes can be cloned and moved from one organism into another and the foreign gene will make the same protein! So a gene from a bacteria can be expressed in plant to make the same protein that was made in the bacteria. The process of taking a gene from one species and expressing it in the genome of another species is referred to as
12. It is interesting that all life on this planet uses information in the form of either DNA, RNA or both; that the same bases are used; and, that the genetic code is almost always the same using three of those bases to code for one of twenty amino acids. (And it’s the same twenty amino acids!) It is also interesting that RNA uses the base Uracil in place of Thymine. The sequence GATTACA in DNA will code for what sequence in RNA?
13. Nearly all the plants available in US grocery stores do not grow in ‘the wild’. Most of our cultivated plants are the result of intensive human intervention over many generations to select for desirable traits, and most of these plants would not even exist without humans. Hybrid corn was first commercialized on a large scale in the US in the 1930s and now, because of vastly improved yields these varieties dominate the $42 billion yr corn crop in the US. Hybrid corn
14. There is an interesting parallel between the language of DNA and our own written language (Is this a coincidence?). A nucleotide is like a letter (not much information); a triplet, or codon, is like a word (slightly better, a word has meaning); a gene, then would be like a paragraph and a chromosome would be like a one volume of a set of encyclopedias with the whole set being like the entire genome. A genetic construct used for crop improvement is
15. Genetically engineered crops are now grown:
16. A GMO is
17. “Ordinary Tomatoes Do Not Contain Genes, while Genetically Modified Ones Do”
18. The sequence of DNA that is called a gene codes for a protein using DNA’s four letter code. Three bases will code for one of twenty amino acids. When a gene is expressed, messenger RNA is transcribed from the DNA template and translated into a protein in the cytoplasm. If a single base in the sequence is missing, this mutation could