Basics of DNA Replication Quiz

PDF page 568: The Watson and Crick model suggested a way in which DNA could be replicated during cell division. Basically, the two strands unwind and separate where the hydrogen bonds connect the nucleotides. Each parental strand then serves as a template for a new, complementary daughter strand. Replication is said to be semi-conservative because the original information encoded in each parental strand is conserved (kept) in the daughter molecules. Thus, a newly replicated molecule of DNA consists of one “old” strand and one “new” strand. Meselson and Stahl used density differences in nitrogen isotopes to investigate replication, and their experiments supported the semi-conservative model. However, the process of replication is more complex than their model’s simple description. Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 and Big Idea

PDF page 570: between N and N, and the other corresponded to the band of N DNA. These results could only be explained if DNA replicates in a semi-conservative manner. Therefore, the other two modes were ruled out. During DNA replication, each of the two strands that make up the double helix serves as a template from which new strands are copied. The new strand will be complementary to the parental or “old” strand. When two daughter DNA copies are formed, they have the same sequence and are divided equally into the two daughter cells.

PDF page 568: The Watson and Crick model suggested a way in which DNA could be replicated during cell division. Basically, the two strands unwind and separate where the hydrogen bonds connect the nucleotides. Each parental strand then serves as a template for a new, complementary daughter strand. Replication is said to be semi-conservative because the original information encoded in each parental strand is conserved (kept) in the daughter molecules. Thus, a newly replicated molecule of DNA consists of one “old” strand and one “new” strand. Meselson and Stahl used density differences in nitrogen isotopes to investigate replication, and their experiments supported the semi-conservative model. However, the process of replication is more complex than their model’s simple description. Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 and Big Idea

PDF page 569: In conservative replication, the parental DNA remains together, and the newly formed daughter strands are together. The semi-conservative method suggests that each of the two parental DNA strands act as a template for new DNA to be synthesized; after replication, each double-stranded DNA includes one parental or “old” strand and one “new” strand. In the dispersive model, both copies of DNA have double-stranded segments of parental DNA and newly synthesized DNA interspersed. Meselson and Stahl were interested in understanding how DNA replicates. They grew E. coli for several generations in a

PDF page 568: The Watson and Crick model suggested a way in which DNA could be replicated during cell division. Basically, the two strands unwind and separate where the hydrogen bonds connect the nucleotides. Each parental strand then serves as a template for a new, complementary daughter strand. Replication is said to be semi-conservative because the original information encoded in each parental strand is conserved (kept) in the daughter molecules. Thus, a newly replicated molecule of DNA consists of one “old” strand and one “new” strand. Meselson and Stahl used density differences in nitrogen isotopes to investigate replication, and their experiments supported the semi-conservative model. However, the process of replication is more complex than their model’s simple description. Information presented and the examples highlighted in the section support concepts outlined in Big Idea 3 and Big Idea

PDF page 570: between N and N, and the other corresponded to the band of N DNA. These results could only be explained if DNA replicates in a semi-conservative manner. Therefore, the other two modes were ruled out. During DNA replication, each of the two strands that make up the double helix serves as a template from which new strands are copied. The new strand will be complementary to the parental or “old” strand. When two daughter DNA copies are formed, they have the same sequence and are divided equally into the two daughter cells.

PDF page 569: The Science Practice Challenge Questions contain additional test questions for this section that will help you prepare for the AP exam. These questions address the following standards: [APLO 2.34][APLO 3.3][APLO 4.1] The elucidation of the structure of the double helix provided a hint as to how DNA divides and makes copies of itself. This model suggests that the two strands of the double helix separate during replication, and each strand serves as a template from which the new complementary strand is copied. What was not clear was how the replication took place. There were three models suggested (Figure 14.12): conservative, semi-conservative, and dispersive.

PDF page 569: In conservative replication, the parental DNA remains together, and the newly formed daughter strands are together. The semi-conservative method suggests that each of the two parental DNA strands act as a template for new DNA to be synthesized; after replication, each double-stranded DNA includes one parental or “old” strand and one “new” strand. In the dispersive model, both copies of DNA have double-stranded segments of parental DNA and newly synthesized DNA interspersed. Meselson and Stahl were interested in understanding how DNA replicates. They grew E. coli for several generations in a

PDF page 569: In conservative replication, the parental DNA remains together, and the newly formed daughter strands are together. The semi-conservative method suggests that each of the two parental DNA strands act as a template for new DNA to be synthesized; after replication, each double-stranded DNA includes one parental or “old” strand and one “new” strand. In the dispersive model, both copies of DNA have double-stranded segments of parental DNA and newly synthesized DNA interspersed. Meselson and Stahl were interested in understanding how DNA replicates. They grew E. coli for several generations in a

PDF page 569: medium containing a “heavy” isotope of nitrogen ( N) that gets incorporated into nitrogenous bases, and eventually into the DNA (Figure 14.13).

PDF page 569: medium containing a “heavy” isotope of nitrogen ( N) that gets incorporated into nitrogenous bases, and eventually into the DNA (Figure 14.13).

PDF page 570: band at a higher density position than that grown in N. Meselson and Stahl noted that after one generation of growth in

PDF page 570: N after they had been shifted from N, the single band observed was intermediate in position in between DNA of cells

PDF page 570: harvested from cells grown for two generations in N formed two bands: one DNA band was at the intermediate position

PDF page 570: harvested from cells grown for two generations in N formed two bands: one DNA band was at the intermediate position

PDF page 570: N after they had been shifted from N, the single band observed was intermediate in position in between DNA of cells

PDF page 570: grown exclusively in N and N. This suggested either a semi-conservative or dispersive mode of replication. The DNA

PDF page 570: allowed to grow for one more life cycle in N and spun again. During the density gradient centrifugation, the DNA is loaded into a gradient (typically a salt such as cesium chloride or sucrose) and spun at high speeds of 50,000 to 60,000