Chapter 17: From Gene to Protein

Question 1

5’ cap

Answer 1

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

Question 2

alternative RNA splicing

Answer 2

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 3

codon

Answer 3

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 4

domains

Answer 4

(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 5

E site

Answer 5

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 6

frameshift mutation

Answer 6

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 7

gene expression

Answer 7

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 function as RNAs.

Question 8

insertion

Answer 8

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

Question 9

intron

Answer 9

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 10

mutagen

Answer 10

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

Question 11

mutation

Answer 11

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

Question 12

nonsense mutation

Answer 12

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

Question 13

nucleotide-pair substitution

Answer 13

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 14

P site

Answer 14

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 15

point mutation

Answer 15

A change in a single nucleotide pair of a gene.

Question 16

poly-A tail

Answer 16

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

Question 17

polyribosome (polysome)

Answer 17

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

Question 18

primary transcript

Answer 18

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

Question 19

promoter

Answer 19

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 20

ribozyme

Answer 20

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

Question 21

signal peptide

Answer 21

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 22

signal-recognition particle (SRP)

Answer 22

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 23

silent mutation

Answer 23

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 24

spliceosome

Answer 24

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 25

TATA box

Answer 25

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

Question 26

template strand

Answer 26

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

Question 27

terminator

Answer 27

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 28

transcription

Answer 28

The synthesis of RNA using a DNA template.

Question 29

transcription factor

Answer 29

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

Question 30

transcription initiation complex

Answer 30

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

Question 31

transcription unit

Answer 31

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

Question 32

transfer RNA (tRNA)

Answer 32

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 33

translation

Answer 33

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 34

triplet code

Answer 34

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

Question 35

wobble

Answer 35

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.