biology ch. 9
deoxyribose
a five-carbon sugar molecule with a hydrogen atom rather that a hydroxyl group in the 2' position; the sugar component of DNA nucleotides
mismatch repair
a form of DNA repair in which non-complementary nucleotides are recognized, excised, and replaced with correct nucleotides
nucleotide excision repair
a form of DNA repair in which the DNA molecule in unwound and separated in the region of the nucleotide damage, the damaged nucleotides are removed and replaced with new nucleotides using the complementary strand, and the DNA strand is resealed and allowed to rejoin its complement
phosphate group
a molecular group consisting of a central phosphorus atom bound to four oxygen atoms
nitrogenous base
a nitrogen-containing molecule that acts as a base; often referring to one of the purine or pyrnidine components of nucleic acids
mutaion
a permanent variation in the nucleotide sequence of a genome
alternative RNA splicing
a post-trascriptional gene regulation mechanism in eukaryotes in which multiple protein products are produced by a single gene through alternative splicing combinations of the RNA transcript
promoter
a sequence on DNA to which RNA polymerase and associated factors bind and initiate transcription
exon
a sequence present in protein-coding mRNA after completion of pre-mRNA splicing
primer
a short stretch of RNA nucleotides that is required to initiate replication and allow DNA polymerase to bind and begin replication
telomerase
an enzyme that contains a catalytic part and an inbuilt RNA template; in functions to maintain telomeres at chromosome ends
helicase
an enzyme that helps to open up the DNA helix during DNA replication by breaking the hydrogen bods
DNA polumerase
an enzyme that synthesizes a new strand of DNA complementary to a template strand
RNA polymerase
an enzyme that synthesizes an RNA strand from a DNA template strand
post-translational
control of gene expression after a protein has been created
post-transcriptional
control of gene expression after the RNA molecule has been created but before it is translated into protein
epigenetic
describing non-genetic regulatory factors, such as changes in modifications to histone proteins and DNA that control accessibility to genes in chromosomes
lagging strand
during replication of the 3' to 5' strand, the strand that is replicated in short fragments and away from the replication fork
mRNA
messenger RNA; a form of RNA that carries the nucleotide sequence code for a protein sequence that is translated into a polypeptide sequence
intron
non-protein-coding intervening sequences that are spliced from mRNA during processing
stop codon
one of the three-mRNA codons that specifies termination of translation
gene expression
processes that control whether a gene is expressed
rRNA
ribsomal RNA; molecules of RNA that combine to form part of the ribosome
start codon
the AUG on a mRNA from which translation begins; always specifies methionine
telomere
the DNA at the end of linear chromosomes
Okazai framents
the DNA fragments that are synthesized in short streches on the lagging strand
replication fork
the Y-shaped structure formed during the initiation of replication
genetic code
the amino acids that correspond to three-nucleotide codons of mRNA
DNA ligase
the enzyme that catalyzes the joining of DNA fragments together
semiconservative replication
the method used to replicate DNA in which the double-stranded molecule is separated and each strand acts as a template for a new strand to be synthesized, so the resulting DNA molecules are composed of one new strand of nucleotides and one old strand of nucleotides
double helix
the molecular shape of DNA in which two strands of nucleotides wind around each other in a spiral shape
splicing
the process of removing introns and reconnecting exons in a pre-mRNA
transcription bubble
the region of locally unwound DNA that allows for transcription of mRNa
nontemplate strand
the strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA
template strand
the strand of DNA that specifies the complementary mRNA molecule
leading strand
the strand that is synthesized continuously in the 5' to 3' direction that is synthesized in the direction of the replication fork
codon
three consecutive nucleotides in mRNA that spectify the addition of a specific amino acid or the release of a polypeptide chain during translation
tRNA
transfer RNA; and RNA molecule that contains a specific three-nucleotides anticodon sequence to pair with the mRNA codon and also binds to a specific amino acid