 | Term | Definition |
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Bacteriophage |
A virus that infects bacteria; also called a phage. |
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32P and 35S |
Radioactive material used to help determine if genetic material was located in the DNA or proteins. |
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Centrifuge |
An apparatus that rotates at high speed and by centrifugal force separates substances of different densities, as milk and cream. |
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Phage head |
The part of the bacteriophage that contains the DNA. |
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Double helix |
The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape. |
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Helix |
A spiral form or structure; one strand of DNA makes this shape. |
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Base pairing |
Adenine is paired with thymine; Guanine is paired with cytosine. |
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5' |
The starting location of DNA replication. It goes from here to the 3' end of the replicated DNA. |
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3' |
The ending location of DNA. It goes from the 5' end of the replicated DNA to here. |
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Template strand |
The DNA strand that provides the template for ordering the sequence of nucleotides in an RNA transcript. |
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Complimentary strand |
The DNA strand that is created by RNA transcript. |
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Origin of replication |
Site where the replication of a DNA molecule begins. |
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Replication fork |
A Y-shaped region on a replicating DNA molecule where new strands are growing. |
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DNA polymerase |
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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DNA primase |
An enzyme that joins RNA nucleotides to make the primer. |
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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. |
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Leading strand |
The new continuous complimentary DNA strand synthesized along the template strand in the madatory 5' to 3' direction. |
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Lagging strand |
A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork. |
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Primer |
A polynucleotide with a free 3' end, bound by complimentary base pairing to the template strand, that is elongated during DNA replication. |
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Excision repair |
The process of removing and then correctly replacing a damaged segment of DNA using the undamaged strand as a guide. |
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Nucleotide sequence |
The order in which the nucleotides in DNA and RNA are arranged. |
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RNA polymerase |
An enzyme that links together the growing chain of ribonucleotides during transcription. |
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Uracil |
The RNA version of thymine. Like thymine, this base also pairs with adenine. |
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Promoter |
A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA. |
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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. |
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Initiation (RNA synthesis) |
The process in RNA synthesis where after RNA polymerase binds to the promoter, the DNA strands unwind, and the polymerase initiates RNA synthesis at the start point on the template strand. |
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Elongation (RNA synthesis) |
In RNA synthesis, the process where the polymerase moves downstream, unwinding the DNA and elongating the RNA transcript 5' to 3' in the wake of transcription, the DNA strands re-form a double helix. |
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Termination (RNA synthesis) |
In RNA synthesis, the process where the RNA transcript is eventually released and the polymerase detaches from the DNA. |
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RNA transcript |
A region of a DNA molecule that is transcribed into an RNA molecule. |
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Transcription |
The synthesis of RNA on a DNA template. |
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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. |
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Triplet code |
A set of three-nucleotide-long words that specify the amino acids for polypeptide chains. |
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Codon |
A three-nucleotide sequence of DNA or mRNA that specifies a paticular amino acid or termination signal; the basic unit of the genetic code. |
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mRNA |
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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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; also called transfer RNA. |
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rRNA |
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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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. |
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GTP |
Similar to ATP, this is also used for energy transfer by breaking its phosphate bonds. |
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Anticodon |
A specialized base triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule. |
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Aminoacyl-tRNA synthetase |
An enzyme that joins each amino acid to the correct tRNA. |
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Activated amino acid |
a tRNA bonded with its corresponding amino acid; also called aminoacyl tRNA. |
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5' to 3' |
The direction in which DNA/RNA is transcripted (hint: #' to #'). |
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N-terminus |
The amino end of the methionine in an RNA. |
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C-terminus |
The carboxyl end of the amino acid in an RNA. |
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Start codon |
AUG; the codon that begins all RNA. |
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Stop codon |
UAG, UAA, or UGA; the codon that ends all RNA. |
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Initiation (protein synthesis) |
The process in protein synthesis in which the AUG codon is matched up with the tRNA anticodon and the methionine amino acid. The tRNA and the mRNA are connected via the codon/anticodon pairings in the ribosome. |
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Elongation (protein synthesis) |
The process in protein synthesis in which different codons are matching up with different tRNA anticodons, thus elongating the amino acid chain. |
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Termination (protein synthesis) |
The process in protein synthesis in which a UAG, UAA, or UGA codon is in the ribosome. A stop codon comes into the ribosome and connects itself with one of these codons and halts the production of the amino acid. |
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A site |
One of a ribosome's three binding sites for tRNA during translation. This site in the ribosome holds the tRNA carrying the next amino acid to be added to the polypeptide chain. |
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P site |
One of a ribosome's three binding sites for tRNA during translation. This site holds the tRNA carrying the growing polypeptide chain. |
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Polyribosome |
An aggregation of several ribosomes attached to one mRNA molecule. |
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Signal peptide |
A stretch of amino acids on a polypeptide that targets the protein to a specific destination in a eukaryotic cell. |
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Signal recognition particle (SRP) |
A protein-RNA complex that recognizes a signal peptide as it emerges from the ribosome. |
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Point mutation |
A change in a gene at a single nucleotide pair. |
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Insertion |
A mutation involving the addition of one or more nucleotide pairs to a gene. |
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Deletion |
A mutational loss of one or more nucleotide pairs from a gene. |
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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. |
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Missence 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. |
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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. |
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Silent mutation |
A mutation that changes a single nucleotide, but does not change the amino acid created. |
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5' cap |
The 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide. |
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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. |
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Splicing |
Removing the introns of an mRNA molecule before it goes out of the nucleus into the cytoplasm for translation. |
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Exon |
A coding region of a eukaryotic gene that are separated from each other by introns. These regions are expressed in the gene. |
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Intron |
A noncoding, intervening sequence within a eukaryotic gene. |
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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. |
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Transcription factor |
A regulatory protein that binds to DNA and stimulates transcription of specific genes. |
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