Chemistry 101 Fall 2019 · 2019-10-21 · •All genetic information is stored in the nucleus of the millions of cells in the body. •Each nucleus contains chromosomes, 46 compact
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How Can Corn be Made to Resist Herbicide or Create its Own Insecticide?
Each cell of the corn plant has a complete set of instructions on how to grow and reproduce
• This information passes from generation to generation and is calledthe genome
• Genes are short sections of instructions that govern specificreactions, chemicals, or events in the cell
• If a gene is changed, then an inheritable trait changes (such asmaking corn produce a new chemical, such as an insecticide)
• A soil bacterium (Bacillus thuringiensis) has the genes to makeinsecticidal proteins, so by taking a gene out of the bacteria andinserting it into the corn plant, we have corn plants that producean insecticidal protein
• All genetic information is stored in the nucleus of the millions of cells in the body.
• Each nucleus contains chromosomes, 46 compact structures of intertwined molecules of DNA, and about 30,000 genes, components that convey one or more hereditary traits.
• DNA is a special template written in a molecular code on a tightly coiled thread that carries all genetic information.
A typical DNA molecule consists of thousands of nucleotides covalently bonded in a long chain.
The phosphate groups are responsible for linking each nucleotide.
A phosphate group of one nucleotide reacts with an –OH group present on the deoxyribose ring of another nucleotide, forming and eliminating a H2O molecule.
X-Ray Diffraction pattern of a hydrated DNA molecule taken in 1952.
This technique uses the fact that a molecule’s electrons diffract X-Rays at particular angles and the resulting pattern, like the one above, can be used to solve the structure of a crystal.
Chargaff’s RuleErwin Chargaff’s research showed that for all humans, the percentage of adenine in DNA is almost identical to the percentage of thymine.
Similarly, the percentages of guanine and cytosine are almost equal.
From this, Chargaff concluded that the bases always come in pairs; adenine is always associated with thymine and guanine is always associated with cytosine.
ProteinsProteins are made of amino acids. The general formula for an amino acid includes four groups attached to a carbon atom: (1) a carboxylic acid group, -COOH; (2) an amine group, -NH2; (3) a hydrogen atom, -H; and (4) a side chain designated as R:
There are 20 naturally occurring amino acids that make up proteins
They differ from one another by the different R groups
CodonsCodons: How are they relevant in genetic expression?
The order of bases in DNA determines the order of amino acids in a protein.
Because there are 20 amino acids present in the proteins, the DNA code must contain 20 code “words”; each word represents a different amino acid.
The genetic code is written in groupings of three DNA bases, called codons.
The diagram shows possible codons, determined according to the base sequence of the nucleic acid strand. The expression of the genetic information is then seen through the specific proteins assigned.
Sickle Cell AnemiaThe function of a protein is dependent on its shape or three-dimensional structure.
Small changes in the primary structure can have dramatic effects on its properties.
Sickle cell anemia is an example of a condition that develops when red blood cells take on distorted shapes due to an error in the amino acid sequence.
Because these cells lose their normal shape, they cannot pass through tiny openings in the spleen and other organs.
Some of the sickled cells are destroyed and anemia results. Other sickled cells can clog organs so badly that the blood supply to them is reduced.
Other Reasons for Genetic Engineering•Make crops more resistant to disease, tolerant of stresses (salt, heat, or drought)• Develop soybeans that produce high yields of biofuel per acre• Use of enzymes to create new drugs• Develop vaccines that grow in edible products