Chapter 17 - From Gene to Protein

Question 1

gene expression

Answer 1

The process by which information encoded in DNA directs the synthesis of proteins or, in some cases, RNAs that are not translated into proteins and instead functions as RNAs.

Question 2

transcription

Answer 2

The synthesis of RNA using a DNA template.

Question 3

messenger RNA (mRNA)

Answer 3

A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein. (In eukaryotes, the primary RNA transcript must undergo RNA processing to become mRNA).

Question 4

translation

Answer 4

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.

Question 5

ribosome

Answer 5

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. <em>See also</em> nucleolus.

Question 6

primary transcript

Answer 6

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

Question 7

triplet code

Answer 7

A genetic information system in which a set of three-nucleotide-long words specify the amino acids for polypeptide chains.

Question 8

template strand

Answer 8

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

Question 9

codon

Answer 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.

Question 10

reading frame

Answer 10

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

Question 11

RNA polymerase

Answer 11

An enzyme that links ribonucleotides into a growing RNA chain during transcription, based on the complementary binding to nucleotides on a DNA template strand.

Question 12

promoter

Answer 12

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

Question 13

terminator

Answer 13

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.

Question 14

transcription unit

Answer 14

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

Question 15

start point

Answer 15

In transcription, the nucleotide position in the promoter where RNA polymerase begins synthesis of RNA.

Question 16

transcription factor

Answer 16

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

Question 17

transcription initiation complex

Answer 17

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

Question 18

TATA box

Answer 18

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

Question 19

RNA processing

Answer 19

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

Question 20

5’ cap

Answer 20

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

Question 21

poly-A tail

Answer 21

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

Question 22

RNA splicing

Answer 22

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

Question 23

intron

Answer 23

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.

Question 24

exon

Answer 24

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.

Question 25

spliceosome

Answer 25

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.

Question 26

ribozyme

Answer 26

An RNA molecule that functions as an enzyme, such as an intron that catalyzes its own removal during RNA splicing.

Question 27

alternative RNA splicing

Answer 27

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.

Question 28

domain

Answer 28

(1) A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. (2) A discrete structural and functional region of a protein.

Question 29

transfer RNA (tRNA)

Answer 29

An RNA molecule that functions as a translator between nucleic acid and protein languages by carrying specific amino acids to the ribosome, where they recognize the appropriate codons in the mRNA.

Question 30

anticodon

Answer 30

A nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on an mRNA molecule.

Question 31

aminoacyl-tRNA synthetase

Answer 31

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

Question 32

wobble

Answer 32

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.

Question 33

ribosomal RNA (rRNA)

Answer 33

RNA molecules that, together with proteins, make up ribosomes; the most abundant type of RNA.

Question 34

P site

Answer 34

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.)

Question 35

A site

Answer 35

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.)

Question 36

E site

Answer 36

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.)

Question 37

polyribosome (polysome)

Answer 37

A group of several ribosomes attached to, and translating, the same messenger RNA molecule.

Question 38

signal peptide

Answer 38

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.

Question 39

signal-recognition particle (SRP)

Answer 39

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.

Question 40

mutation

Answer 40

A change in the nucleotide sequence of an organism’s DNA or in the DNA or RNA of a virus.

Question 41

point mutation

Answer 41

A change in a single nucleotide pair of a gene.

Question 42

nucleotide-pair substitution

Answer 42

A type of point mutation in which one nucleotide in a DNA strand and its partner in the complementary strand are replaced by another pair of nucleotides.

Question 43

silent mutation

Answer 43

A nucleotide-pair substitution that has no observable effect on the phenotype; for example, within a gene, a mutation that results in a codon that codes for the same amino acid.

Question 44

missense mutation

Answer 44

A nucleotide-pair substitution that results in a codon that codes for a different amino acid.

Question 45

nonsense mutation

Answer 45

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

Question 46

insertion

Answer 46

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

Question 47

deletion

Answer 47

(1) A deficiency in a chromosome resulting from the loss of a fragment through breakage. (2) A mutational loss of one or more nucleotide pairs from a gene.

Question 48

frameshift mutation

Answer 48

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

Question 49

mutagen

Answer 49

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