AP Bio Midterm Key Terms Ch. 16 Flashcards
bacteriophage
A virus that infects bacteria; also called a phage.
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3’ end of a new DNA fragment to the 5’ end of a growing chain.
DNA polymerase
An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.
double helix
for of native DNA, referring to its adjacent polynucleotide strands wound into a spiral shape
helicase
enzyme that untwists the double helix of DNA at the replication forks
lagging strand
a discontinuously synthesized DNA strand that elongates in a direction away from the replication fork
leading strand
new continuous complementary DNA strand synthesized along the template strand in the mandatory 5’ to 3’ direction
mismatch repair
cellular process that uses special enzymes to fix incorrectly paired nucleotides
nuclease
enzyme that hydrolyzes DNA and RNA into their component nucleotides
nucleotide excision repair
process of removing and then correctly replacing a damaged segment of DNA using the undamaged strand as a guide
Okazaki fragment
short segment of DNA synthesized on a template strand during DNA replication; many Okazaki fragments make up the lagging strand of newly synthesized DNA
origin of replication
site where the replication of a DNA molecule begins
phage
a virus that infects bacteria; also called a bacteriophage
primase
an enzyme that joins RNA nucleotides to make the primer
primer
A polynucleotide with a free 3´ end, bound by complementary base pairing to the template strand, that is elongated during DNA replication.
replication fork
A Y-shaped region on a replicating DNA molecule where new strands are growing.
semiconservative model
Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.
single-strand binding protein
During DNA replication, molecules that line up along the unpaired DNA strands, holding them apart while the DNA strands serve as templates for the synthesis of complementary strands of DNA.
telomerase
An enzyme that catalyzes the lengthening of telomeres. The enzyme includes a molecule of RNA that serves as a template for new telomere segments.
telomere
The protective structure at each end of a eukaryotic chromosome. Specifically, the tandemly repetitive DNA at the end of the chromosome’s DNA molecule
topoisomerase
A protein that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.
transformation
(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell.
