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Definitions |
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transcription
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process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA
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DNA bases
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adenine, guanine, cytosine, thymine
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semiconservative
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refers to the fact that half of a newly made DNA is the old template.
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antisense strand
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strand of DNA that is NOT transcribed
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RNA polymerase
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an enzyme that pries the 2 strands of DNA apart and hooks together the RNA nucleotides as they base pair along the DNA template
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point mutations
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gene mutations involving changes in one or a few nucleotides
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antiparallel
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The opposite arrangement of the sugar-phosphate backbones in a DNA double helix.
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chaperon proteins
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a type of protein that helps denatured proteins fold correctly
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5' cap
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when pre-mRNA is modified the 5 primed end is synthesized first; it is a modified form of a guanine nucleotide
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leading strand
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the new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' --> 3' direction
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complementary base pairing
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adenine form hydrogen bonds with thymine, cytosine forms hydrogen bonds with guanine
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uracil
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a nitrogen-containing base found in RNA (but not in DNA) and derived from pyrimidine
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E site
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One of a ribosome's three binding sites for tRNA during translation. This site is the place where discharged tRNAs leave the ribosome.
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tRNA
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The type of RNA that binds to specific amino acids and transports them to the ribosome during protein synthesis
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lagging strand
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The strand in replication that is copied 3' to 5' as Okazaki fragments and then joined up.
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ribose
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a pentose sugar important as a component of ribonucleic acid
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topoisomerase
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A protein that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.
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double helix
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The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.
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euchromatin
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a region of DNA that is uncoiled and undergoing active transcription into RNA
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peptide bond
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covalent bond formed between amino acids
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polypeptide
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A polymer (chain) of many amino acids linked together by peptide bonds.
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RNA primase
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An enzyme that creates an RNA primer for initiation of DNA replication.
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DNA polymerase
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An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.
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codons
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A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.
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translation
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(genetics) the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm
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protein synthesis
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the formation of proteins by using information contained in DNA and carried by mRNA
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mutation
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change in a DNA sequence that affects genetic information
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stop codons
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UAA, UAG, UGA
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A site
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holds the tRNA carrying the next amino acid to be added to the chain
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frameshift
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A nucleotide is inserted or deleted, changing where the coding for entirely different amino acids.
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okazaki fragments
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Short fragments of DNA that are a result of the synthesis of the lagging strand during DNA replication.
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rRNA
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The most abundant type of RNA, which together with proteins froms the structure of ribosomes. Ribosomes coordinate the sequential coupling of tRNA molecules to mRNA codons; also called ribosomal RNA.
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heterochromatin
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Densely staining condensed chromosomal regions, believed to be for the most part genetically inert. chromatin that remains tightly coiled (and darkly staining) throughout the cell cycle.
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anticodon
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group of three bases on a tRNA molecule that are complementary to an mRNA codon
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helicase
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an enzyme that untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands
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mRNA
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A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein; also called messenger RNA.
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introns
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sequence of DNA that is not involved in coding for a protein
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nucleotides
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Basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases
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phosphodiester bonds
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bonds that join nucleotides in nucleic acids
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ribonucleic acid
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(RNA) part of the genetic material that organisms inherited from their parents
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P site
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one of a ribosome's three binding sites for tRNA during translation. It holds the tRNA carrying the growing polypeptide chain.
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sense strand
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The strand of DNA that has the code for protein
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chaperonins
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protein molecules that assist the proper folding of other proteins
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poly(A) tail
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After an mRNA is transcribed from a gene, the cell adds a stretch of A residues (typically 50-200) to its 3' end.
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nonsense
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A new nucleotide replaces an existing one and changes the codon so that it codes for the end of the strand with TAA, TAG, or TGA.
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DNA ligase
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an enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments
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genetic code
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the ordering of nucleotides in DNA molecules that carries the genetic information in living cells
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replication fork
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A Y-shaped region on a replicating DNA molecule where new strands are growing.
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exons
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expressed sequence of DNA; codes for a protein
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missense
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single base change results in the inclusion of a different amino acid
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