Chapter 4. DNA, RNA, and the Flow of Genetic Information Flashcards
in elongation of polymers, the initial segment of the polymer that is to be extended and on which elongation is dependent.
Primer
template for protein synthesis. The base sequence of mRNA is complimentary to a gene in DNA.
Messenger RNA (mRNA)
A nitrogenous base that includes a pyrimidine ring fused with a five-membered imidazole ring; the purine derivatives adenine and guanine are found in nucleotides and nucleic acids.
Purine
a purine or pyrimidine base linked to a sugar.
Nucleoside
a nitrogenous base that is a six-membered heterocyclic ring containing two nitrogen and four carbon atoms; the pyrimidine derivatives cytosine, uracil and thymine are found in nucleotides and nucleic acids.
Pyrimidine
a five-carbon monosaccharide (C5H9O5) that constitutes the carbohydrate moiety of deoxynucleotides; the deoxyribose commonly found in these molecules is 2-deoxyribose.
Deoxyribose
a nitrogenous purine or pyrimidine base linked to a sugar that is in turn linked to one or more phosphate groups.
Nucleotide
a large ribonucleoprotein assembly that catalyzes the formation of peptide bonds; a molecular machine that coordinates protein synthesis.
Ribose
enzymes that catalyze the template-directed, primer-dependent addition of deoxynucleotide units, using deoxynucleotide triphosphates as substrates, to the 3’ end of the DNA chain; chain growth is in the 5’-to 3’-direction; such enzymes replicate and repair DNA.
DNA polymerase
an enzyme that synthesizes DNA using an RNA template.
Reverse transcriptase
A right-handed double helix with the following characteristics: the two strands are antiparallel; the bases are inside the helix and the phosphates and deoxyribose sugars are on the outside; adenine forms hydrogen bonds with thymine, and guanine forms them with cytosine; the bases in each pair are coplanar; there are 10.4 residues per turn, with a pitch of 35 Å.
B-DNA
A structure composed of two intertwined DNA strands such that the sugar-phosphate backbone lies on the outside and the bases on the inside. The two strands run in opposite directions.
double helix
A right-handed double helix made up of antiparallel strands held together by A-T and G-C base pairing; it is wider and shorter than B-DNA and is seen in dehydrated DNA as well as in doublestranded regions of RNA and in RNA-DNA helices.
A-DNA
the relationship between nucleic acid sequence information and protein sequence information.
Genetic code
A linear polymer of nucleotide monomers joined by 3’ to 5’ phosphodiester linkages; each monomer consists of a sugar, a phosphate, and one of four bases. Two of the bases are derivatives of purine - adenine (A) and guanine (G) - and two of pyrimidine - cytosine (C) and thymine (T). The sugar units in DNA are deoxyriboses.
deoxyribonucleic acid (DNA)
generation of unique but related mRNA molecules by the differential splicing of the pre-mRNA transcript. By allowing the synthesis of more than one mRNA from a pre-mRNA transcript, alternative splicing increases the coding potential of the genome.
Alternative splicing
regions of the pre-mRNA that are retained in the mature mRNA.
Exon
a hypothesis that suggests that new proteins arose in evolution by rearranging exons that encoded discrete structural elements.
Exon shuffling
regions of the primary transcript that are removed in the mature mRNA; also called intervening sequences.
Intron
nucleotide triplet in mRNA that codes for a particular amino acid.
Codon
Three-nucleotide sequence of tRNA that base-pairs with a codon in mRNA.
Anticodon
RNA molecule 22-nucleotides in length that possesses the regulatory activity when bound to members of a class of proteins called the Argonaute family.
Micro RNA (miRNA)
A class of small RNA molecules that bind to mRNA and facilitate its degradation.
Small interfering RNA (siRNA)
the duplication of DNA in which one of the strands of each daughter molecule is newly synthesized while the other is unchanged from the parental DNA double helix.
Semiconservative replication
