Chapter 17 - From Gene To Protein

Front 1

5' cap

Back 1

A modified form of guanine nucleotide added onto the nucleotide at the 5' end of a pre-mRNA molecule.

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A site

Back 2

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.)

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alternative RNA splicing

Back 3

A type of eukaryotic gene 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.

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amino acid

Back 4

An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of polypeptides.

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aminoacyl-tRNA synthetase

Back 5

An enzyme that joins each amino acid to the appropriate tRNA.

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anticodon

Back 6

A nucleotide triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.

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base-pair substitution

Back 7

A type of point mutation; the replacement of one nucleotide and its partner in the complementary DNA strand by another pair of nucleotides.

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chaperonin

Back 8

A protein molecule that assists in the proper folding of other proteins.

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codon

Back 9

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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domain

Back 10

(1) A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. (2) An independently folding part of a protein.

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E site

Back 11

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.)

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endomembrane system

Back 12

The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and vacuoles.

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exon

Back 13

A sequence within a primary transcript that remains in the RNA after RNA processing; also refers to the region of DNA from which this sequence was transcribed.

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frameshift mutation

Back 14

A mutation occurring when the number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the subsequent nucleotides into codons.

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gene expression

Back 15

The process by which DNA directs the synthesis of proteins or, in some cases, just RNAs.

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insertion

Back 16

A mutation involving the addition of one or more nucleotide pairs to a gene.

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intron

Back 17

A noncoding, intervening sequence within a primary transcript that is removed from the transcript during RNA processing; also refers to the region of DNA from which this sequence was transcribed.

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messenger RNA (mRNA)

Back 18

A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.

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mutagen

Back 19

A chemical or physical agent that interacts with DNA and causes a mutation.

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mutation

Back 20

A change in the nucleotide sequence of an organism’s DNA, ultimately creating genetic diversity. Mutations also can occur in the DNA or RNA of a virus.

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nonsense mutation

Back 21

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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P site

Back 22

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.)

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point mutation

Back 23

A change in a gene at a single nucleotide pair.

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poly-A tail

Back 24

A sequence of 50 to 250 adenine nucleotides added onto the 3' end of a pre-mRNA molecule.

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primary transcript

Back 25

An initial RNA transcript; also called pre-mRNA when transcribed from a protein-coding gene.

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promoter

Back 26

A specific nucleotide sequence in DNA that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place.

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radiation

Back 27

The emission of electromagnetic waves by all objects warmer than absolute zero.

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reading frame

Back 28

On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis.

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ribosomal RNA (rRNA)

Back 29

The most abundant type of RNA, which together with proteins makes up ribosomes.

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ribosome

Back 30

A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus. See also nucleolus.

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ribozyme

Back 31

An RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing.

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RNA polymerase

Back 32

An enzyme that links ribonucleotides into a growing RNA chain during transcription.

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RNA processing

Back 33

Modification of RNA transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' and 3' ends.

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RNA splicing

Back 34

After synthesis of a eukaryotic primary RNA transcript, the removal of portions (introns) of the transcript that will not be included in the mRNA.

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signal peptide

Back 35

A sequence of about 20 amino acids at or near the leading (amino) end of a polypeptide that targets it to the endoplasmic reticulum or other organelles in a eukaryotic cell.

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signal-recognition particle (SRP)

Back 36

A protein-RNA complex that recognizes a signal peptide as it emerges from a ribosome and helps direct the ribosome to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER.

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spliceosome

Back 37

A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.

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TATA box

Back 38

A DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex.

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template strand

Back 39

The DNA strand that provides the pattern, or template, for ordering the sequence of nucleotides in an RNA transcript.

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terminator

Back 40

In bacteria, a sequence of nucleotides in DNA that marks the end of a gene and signals RNA polymerase to release the newly made RNA molecule and detach from the DNA.

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transcription

Back 41

The synthesis of RNA using a DNA template.

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transcription factor

Back 42

A regulatory protein that binds to DNA and affects transcription of specific genes.

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transcription initiation complex

Back 43

The completed assembly of transcription factors and RNA polymerase bound to a promoter.

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transcription unit

Back 44

A region of DNA that is transcribed into an RNA molecule.

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transfer RNA (tRNA)

Back 45

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.

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translation

Back 46

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

Back 47

A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.

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wobble

Back 48

Flexibility in the base-pairing rules in which the nucleotide at the 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.