Medical Biology P5
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. For this reason, DNA replication is called semiconservative replication. 5. The DNA double helix is unwounded by an enzyme called DNA helicase. Daughter DNA strands are synthesized by the enzyme DNA polymerase. In eukaryotic cells, the daughter DNA strands are synthesized in pieces; these pieces are joined by the enzyme DNA ligase. 6. Sometimes, mistakes are made during DNA replication. If uncorrected, these mistakes are called mutations. When a single nucleotide is changed, this is called a point mutation, or nucleotide substitution.
1. Draw the general structure of a nucleotide. Which parts are identical in all nucleotides, and which can vary? The phosphate group and the sugar called deoxyribose remain consistent, while the nitrogen-containing base varies from (A) adenine, (G) guanine, (T) thymine, or (C) cytosine.
2. Name the four types of nitrogen-containing bases found in DNA. (A) adenine, (G) guanine, (T) thymine, or (C) cytosine
3. Which bases are complementary to one another? How are they held together in the double helix of DNA? Adenine is complementary to thymine, while guanine is complementary to cytosine. They are held together in the double helix of DNA by the covalent...