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Glossary of Chapter 16 - The Molecular Basis of Inheritance

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Bacteriophages
often used in molecular genetics studies; viruses that infect bacteria
Semiconservative model
a model of DNA replication posited by Francis and Crick that postulates that the replication of a DNA strand yields two daughter strands, each identical to the original and each containing one half of the original strand
Origins of replication
specific sites on the DNA molecule where replication begins
Replication fork
a Y-shaped region at each end of a replication bubble where the new strands of DNA are elongating
DNA polymerases
enzymes that catalyze the elongation of new DNA at a replication fork
Leading strand
DNA strand made by a polymerase that nestles in the replication fork and moves along the template strand as the fork progresses; 5’ → 3’
Lagging strand
DNA strand made by polymerase that works in the opposite direction of the replication fork
DNA ligase
an enzyme that joins the Okazaki fragments of the lagging strand into a single DNA strand
Primer
the original, preexisting chain found within a cell; a short stretch of RNA about 10 nucleotides long in eukaryotes; required for a DNA polymerase to begin synthesizing the leading strand of new DNA
Primase
an enzyme that joins RNA nucleotides to make the primer
Helicase
an enzyme that untwists the double helix at the replication fork, separating the two old strands
Single-strand binding protein
molecules that line up along the unpaired DNA strands, holding them apart while they serve as templates for the synthesis of new complementary strands
Mismatch repair
a DNA repair mechanism that fixes mistakes that are made when DNA is copied; carried out by DNA polymerase during replication as well as by other protein molecules
Nuclease
a DNA-cutting enzyme that excises the damaged area of a DNA molecule
Excision repair
repair of a damaged region of a DNA molecule carried out by excising the damaged area and inserting the appropriate nucleotides; carried out by nucleases, DNA polymerases, and ligases
Telomeres
special nucleotide sequences at the ends of eukaryotic chromosomal DNA
Telomerase
a special enzyme that catalyzes the lengthening of telomeres; usually not found in multicellular organisms, with the exception of within gamete-producing cells

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