Chapter 11 Bio Review Essay

1140 Words May 20th, 2012 5 Pages
Andrew Eguia
Dr. Harjani
Medical Biology P5
2/14/12
Chapter 11 Review P216 1. DNA consists of subunits called nucleotides. Each subunit consists of three parts: sugar (deoxyribose), phosphate, and base. 2. The subunits of DNA are assembled by linking the sugar of one nucleotide to the phosphate of the next. As it is found in chromosomes, two DNA polymers are bound together into a structure called a double helix. 3. The “base-paring rule” in DNA is that adenine pairs with thymine, and guanine pairs with cytosine. Bases that can form pairs in DNA are called a complementary base pair. 4. When DNA is replicated, two new DNA double helices are formed, each consisting of one parental strand and one new, daughter strand.
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The structure of DNA is compared to that of a spiral ladder. A complementary base pair, held together by a hydrogen bond, creates the “rungs” of the ladder. The sugar and phosphate together create the backbone, or the sides of the ladder. The carbon atoms of the free sugar are numbered 1-5, and the sugar contains two “ends” that contribute to the synthesizing of the backbone: the 3’ and 5’ ends which connect to the phosphate group of the adjacent nucleotide. And now since there are the ends, there will always be one 3’ end not attached to a phosphate group and a phosphate group not attached to a 3’ end at the end of the backbone. The sugar-phosphate backbones of the two strands of a double helix are antiparallel, meaning that they run in different directions. 5. Describe the process of DNA replication. a. DNA helicase enzymes separate the parental strands of a chromosome to form replication bubbles. b. Each replication bubble consists of two replication forks, with unwound DNA strands between the forks. c. DNA polymerase enzymes synthesize new pieces of DNA d. DNA helicase moves along the parental DNA double helix, unwinding it and enlarging the replication bubble. DNA polymerases in the replication bubble synthesize daughter DNA strands. e. DNA ligase joins the small DNA segments into a single daughter strand 6. How do mutations occur? Describe the principle types of mutation.
Despite the accuracy of

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