LESSON+8


 * UNDERSTANDING COMPLEX SENTENCES**

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‍ ‍ ** *Note: ** You might want to have 2 tabs open -- one for these instructions and one for the page you create. ===== 1. Copy the passage below -- "The Structure of DNA." Source: [] 2. Create a "New Page" by clicking on "Pages and Files" and then "New Page." Title it with your first name (**NO LAST NAMES PLEASE**), underscore, and 8 (for lesson # 8). Don't add any tags. 4. On your page, paste the passage and the questions. 5. First, above the passage, make a list of the ten most challenging words. Label this list **"Most Challenging Words."** 6. Next, in the passage locate the **main subject** of __each sentence__ and highlight it in ** blue **. 7. Break each sentence into **small chunks of meaning** (about five or six words) by inserting a diagonal line **( / )** between the phrases (or chunks of words). 8. Finally, think about how to respond to each question, refer to the passage, and answer with __**complete sentences**__. Responses must be in ** your own words **! Do not copy portions of the article and use them as your answers!
 * __ INSTRUCTIONS __**

Passage: The Structure of DNA
Erwin Chargaff analyzed the nitrogenous bases in many different forms of life, concluding that the amount of purines does not always equal the amount of pyrimidines (as proposed by Levene). DNA must carry information from parent cell to daughter cell. It must contain information for replicating itself. It must be chemically stable, relatively unchanging. However, it must be capable of mutational change. Without mutations, there would be no process of evolution. Many scientists were interested in deciphering the structure of DNA, among them were Francis Crick, James Watson, Rosalind Franklin, and Maurice Wilkens. Watson and Crick gathered all available data in an attempt to develop a model of DNA structure. Franklin took X-ray diffraction photomicrographs of crystalline DNA extract, the key to the puzzle. The data known at the time was that DNA was a long molecule, and proteins were helically coiled. DNA is a double helix, with bases to the center (like rungs on a ladder) and sugar-phosphate units along the sides of the helix (like the sides of a twisted ladder). The strands are complementary (deduced by Watson and Crick from Chargaff's data, A pairs with T and C pairs with G, the pairs held together by hydrogen bonds). Purines are Adenine (A) and Guanine (G). Pyrimidines are Cytosine (C) and Thymine (T). The bases are complementary, with A on one side of the molecule you only get T on the other side, similarly with G and C. If we know the base sequence of one strand we know its complement.

__**Questions:**__ 1. Recall what DNA must carry, contain, and be. 2. Clarify why Watson and Crick gathered data about DNA. 3. Compare and contrast purines and pyrimidines.