Chapter 16: The Molecular Basis of Inheritance Flashcards
antiparallel
Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run in opposite 5′ → 3′ directions).
bacteriophages
A virus that infects bacteria; also called a phage
chromatin
The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.
double helix
The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.
euchromatin
The less condensed form of eukaryotic chromatin that is available for transcription.
helicase
An enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands.
heterochromatin
Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.
lagging strand
A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5′ → 3′ direction away from the replication fork.
leading strand
The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5′ → 3′ direction.
mismatch repair
The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides.
nucleoid
A non-membrane-bounded region in a prokaryotic cell where the DNA is concentrated.
origin of replication
Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.
phage
A virus that infects bacteria; also called a bacteriophage.
replication fork
A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized.
semiconservative model
Type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand.
single-strand binding protein
A protein that binds to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA.
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. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer.
virus
An infectious particle incapable of replicating outside of a cell, consisting of an RNA or DNA genome surrounded by a protein coat (capsid) and, for some viruses, a membranous envelope.
