AP Biology Chapter 16 and 17 Vocabulary 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
The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.
helicase
An 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
The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5’ ( 3’ direction.
mismatch repair
The cellular process that uses special enzymes to fix incorrectly paired nucleotides.
nuclease
An enzyme that hydrolyzes DNA and RNA into their component nucleotides.
nucleotide excision repair
The process of removing and then correctly replacing a damaged segment of DNA using the undamaged strand as a guide.
Okazaki fragment
A 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. See also repetitive DNA.
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.
5’ cap
The 5’ end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide.
A site
One of a ribosome’s three binding sites for tRNA during translation. The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain. (A stands for aminoacyl tRNA.)
alternative RNA splicing
A type of regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.
aminoacyl-tRNA synthetase
An enzyme that joins each amino acid to the correct tRNA.
anticodon
A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
base-pair substitution
A type of point mutation; the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides.
codon
A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
deletion
(1) A deficiency in a chromosome resulting from the loss of a fragment through breakage. (2) A mutational loss of one or more nucleotide pairs from a gene.
domain
(1) A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. (2) An independently folding part of a protein.
E site
One of a ribosome’s three binding sites for tRNA during translation. The E site is the place where discharged tRNAs leave the ribosome. (E stands for exit.)
exon
A coding region of a eukaryotic gene. Exons, which are expressed, are separated from each other by introns.
frameshift mutation
A mutation occurring when the number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the following nucleotides into codons.
insertion
A mutation involving the addition of one or more nucleotide pairs to a gene.
intron
A noncoding, intervening sequence within a eukaryotic gene.
messenger RNA (mRNA)
A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.
missense mutation
The most common type of mutation, a base-pair substitution in which the new codon makes sense in that it still codes for an amino acid.
mutagen
A chemical or physical agent that interacts with DNA and causes a mutation.
mutation
A rare change in the DNA of a gene, ultimately creating genetic diversity.
nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
one gene–one polypeptide hypothesis
The premise that a gene is a segment of DNA that codes for one polypeptide.
P site
One of a ribosome’s three binding sites for tRNA during translation. The P site holds the tRNA carrying the growing polypeptide chain. (P stands for peptidyl tRNA.)
point mutation
A change in a gene at a single nucleotide pair.
poly-A tail
The modified end of the 3’ end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides.
polyribosome (polysome)
An aggregation of several ribosomes attached to one messenger RNA molecule.
primary transcript
An initial RNA transcript; also called pre-mRNA when transcribed from a protein-coding gene.
promoter
A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.
reading frame
The way a cell’s mRNA-translating machinery groups the mRNA nucleotides into codons.
ribosomal RNA (rRNA)
The most abundant type of RNA, which together with proteins forms the structure of ribosomes. Ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons.
ribosome
A cell organelle constructed in the nucleolus and functioning as the site of protein synthesis in the cytoplasm; consists of rRNA and protein molecules, which make up two subunits.
ribozyme
An enzymatic RNA molecule that catalyzes reactions during RNA splicing.
RNA polymerase
An enzyme that links together the growing chain of ribonucleotides during transcription.
RNA processing
Modification of RNA before it leaves the nucleus, a process unique to eukaryotes.
RNA splicing
The removal of noncoding portions (introns) of the RNA molecule after initial synthesis.
signal peptide
A stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell.
signal-recognition particle (SRP)
A protein-RNA complex that recognizes a signal peptide as it emerges from the ribosome.
spliceosome
A complex assembly that interacts with the ends of an RNA intron in splicing RNA, releasing the intron and joining the two adjacent exons.
TATA box
A promoter DNA sequence crucial in forming the transcription initiation complex.
template strand
The DNA strand that provides the template for ordering the sequence of nucleotides in an RNA transcript.
terminator
In prokaryotes, a special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene.
transcription
The synthesis of RNA on a DNA template.
transcription factor
A regulatory protein that binds to DNA and stimulates transcription of specific genes.
transcription initiation complex
The completed assembly of transcription factors and RNA polymerase bound to the promoter.
transcription unit
A region of a DNA molecule that is transcribed into an RNA molecule.
transfer RNA (tRNA)
An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
translation
The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of language from nucleotides to amino acids.
triplet code
A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.
wobble
A violation of the base-pairing rules in that the third nucleotide (5’ end) of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3’ end) of a codon.
