Margaret M. Loos
I. Objectives:
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1. To give information about the chemistry of DNA and RNA.
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2. To introduce the concept of a coding mechanism for production of amino acids.
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3. To allow students to manipulate their own code for amino acids.
II. In the course of studying biology you must learn some chemistry. The concept of a molecule of water as two atoms of hydrogen bonded to one atom of oxygen is not new to students. comfortable with 02, oxygen, and CO2, carbon dioxide in respiration and C6H12O as a hexose (6 carbon) sugar in digestion. Adenosine triphosphate, as the primary energy source in muscular tissue, seemed a large molecule but now you will make a big jump into macromolecules. Be assured that the laws that govern those simple molecules still apply in the giant molecules of heredity. It is now believed that there is no chemical reaction in life that a chemist with enough time, technology, and patience couldn’t duplicate.
Molecular weights—comparative
H20 = 18 amu (atomic molecular units)
O2 = 32 amu C6H12O = 144 amu
CO 2= 38 amu Adenosine triphosphate = 372 amu
The macromolecules in genetics can have molecular weights in the hundreds of thousands of amu’s. The macromolecules, called nucleic acids of the cell nucleus, were discovered by F. Meischer in 1897. Like many other scientific discoveries, their real significance was not appreciated for over 50 years, The two kinds of nucleic acids that are present are deoxyribonucleic acid, DNA, and ribonucleic acid, RNA. Evidence shows that DNA is possibly the genetic material of all living organisms.
DNA is composed of a nitrogen-containing base (either purine or a pyrimidine)
(figure available in print form)
(figure available in print form)
——and a
pentose
(5 carbon
sugar
called Deoxyribose) and a
phosphate
.
R N A is composed of the same elements except the sugar is ribose.
(figure available in print form)
Polynucleotides
The chains of units in DNA and RNA are called polynucleotides. (“poly” means many).
Structural Formula:
(figure available in print form)
Diagrammataic Representatic
(figure available in print form)
III. Task:
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1. From information, name the nucleotides; tell what they bond for.
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2. Construct two diagrammatic polynucleotides; example:-GaGTCT and CTCAGA.
Developed from diagrams in Beadle,
The Language of Life
, Garden City, 1966.