10.4 Flashcards
Note 1 —-»
The primary function of DNA is to encode and store genetic information, thereby acting as the molecular basis of heredity. Genes are passed along from one cell to the next during cell division and from one generation to the next during reproduction. The primary function of DNA is to encode and store genetic information, thereby acting as the molecular basis of heredity. Genes are passed along from one cell to the next during cell division and from one generation to the next during reproduction.
Note 2 —-»
Watson and Crick predicted that a cell applies the same rules when copying its genes during each turn of the cell cycle. Each strand becomes a template for the assembly of a complementary strand from a supply of free nucleotides (gray) available within the nucleus. The nucleotides line up one at a time along the template strand in accordance with the base-pairing rules. Enzymes link the nucleotides to form the new DNA strands. The completed new molecules, identical to the parental molecule, are known as daughter DNA (although no gender should be inferred). Watson and Crick’s model predicts that when a double helix replicates, each of the two daughter molecules will have one old strand from the parental molecule and one newly created strand. This model for DNA replication is known as the semiconservative model because half of the parental molecule is maintained (conserved) in each daughter molecule.
Semiconservative Model
Type of DNA replication in which the replicate double helix consists of one old strand, derived from the old molecule, and one newly made strand.
Note 3 —-»
Although the general mechanism of DNA replication is conceptually simple, the actual process is complex, requiring the coordination of more than a dozen enzymes and other proteins. Some of the complexity arises from the need for the helical DNA molecule to untwist as it replicates and for the two new strands to be made roughly simultaneously. Although the general mechanism of DNA replication is conceptually simple, the actual process is complex, requiring the coordination of more than a dozen enzymes and other proteins. Some of the complexity arises from the need for the helical DNA molecule to untwist as it replicates and for the two new strands to be made roughly simultaneously. Another challenge is the speed of the process. E. coli, with about 4.6 million DNA base pairs, can copy its entire genome in less than an hour. Human cells, with more than 6 billion base pairs in 46 chromosomes, require only a few hours. Despite this speed, the process is amazingly accurate; typically, only about one DNA nucleotide per several billion is incorrectly paired. In the next module, we take a closer look at the mechanisms of DNA replication.
How does complementary base pairing make possible the replication of DNA?
When the two strands of the double helix separate, free nucleotides can base-pair along each strand, leading to the synthesis of new complementary strands.
