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AP Biology Activities - Ch. 16 & 20

AP Biology Activities - Ch. 16 & 20 - Additional...

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Additional Activities Chapter 16 Activity: The Hershey Chase Experiment The phage, which infects E. coli , consists of a head, sheath, tail, and base plate made of different proteins. DNA is packaged within the head of the virus. When T2 comes in contact with E. coli , the phage attaches to the bacterium by its tail. Next, the phage injects genetic material into the cell. The genetic material directs bacterial enzymes to produce viral offspring. When the life cycle is complete, 100 to 200 progeny phages have been assembled inside each bacterium. The bacterium breaks open, or lyses, and the phages are released. Since T2 consists of only DNA and protein, Hershey and Chase reasoned that the genetic material must be one of the two components. So they designed an experiment to determine which it is. For their experiment, the scientists prepared T2 phages that either had radioactive DNA or radioactive proteins. Activity: DNA and RNA Structure DNA and RNA are nucleic acids, polymers made of subunits called nucleotides. One difference between DNA and RNA is the type of sugar their nucleotides contain. DNA contains the sugar deoxyribose, while RNA contains the sugar ribose. Ribose has one more oxygen atom than deoxyribose. -the carbon atoms in a nucleotide's sugars are numbered beginning with the carbon atom bonded to the nitrogenous base. DNA and RNA are each composed of four different nucleotides, which differ in their nitrogenous bases. Three of the four bases are the same in DNA and RNA— adenine, guanine, and cytosine. The fourth base in DNA is thymine. In RNA it is uracil. The nitrogenous bases guanine and adenine each have two linked rings of atoms. They are called purines. Cytosine, thymine, and uracil each have a single ring, and these three bases are called pyrimidines. Activity: DNA the Double Helix DNA consists of two complementary strands of nucleotides twisted together to form a double helix. In this space-filling model, each atom is represented by a small sphere. The yellow and red phosphate groups make the two sugar-phosphate backbones easy to spot. They're on the outside of the double helix. Each crossbar is a hydrogen-bonded pair of bases, one from each DNA strand. An adenine is always paired with a thymine, and a guanine with a cytosine. The double helix can also be represented by a ball-and-stick model. A ribbon model is often used, with ribbons for the sugar-phosphate backbones. Activity: DNA Replication: An Overview In principle, copying DNA-- a process called DNA replication-- is very simple. The two complementary DNA strands separate, and because each nucleotide can only pair with its complement-- Nitrogenous  Base Sugar Nucleotide Phosphate  Group
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adenine with thymine and cytosine with guanine -- each strand can be used as a template to build a new complementary strand, producing two DNA molecules. Here is a simplified closeup of replication, showing what happens along one of the template DNA strands. Using a supply of free nucleotides, DNA polymerase
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AP Biology Activities - Ch. 16 & 20 - Additional...

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