Chapter 17

Question 1

The set of triplet code words in DNA (or mRNA) coding for the amino acids of proteins.

Answer 1

genetic code

Question 2

In a nucleic acid, a sequence of three adjacent nucleotides that codes for a specific amino acid.

Answer 2

codon

Question 3

A class of RNA molecules (Mr 25,000 to 30,000), each of which combines covalently with a specific amino acid for use in protein synthesis.

Answer 3

Transfer RNA (tRNA)

Question 4

An aminoacyl ester of a tRNA; the tRNA is charged with an amino acid.

Answer 4

aminoacyl-tRNA:

Question 5

Enzymes that catalyze synthesis of an aminoacyl-tRNA at the expense of ATP energy.

Answer 5

aminoacyl-tRNA synthetases:

Question 6

The site in a ribosome where the aminoacyl-tRNA binds.

Answer 6

A site

Question 7

A specific sequence of three nucleotides in a tRNA, complementary to a codon for an amino acid in an mRNA.

Answer 7

anticodon

Question 8

The process in which the genetic information present in an mRNA molecule specifies the sequence of amino acids during protein synthesis.

Answer 8

translation

Question 9

A code in which a single element in one language is specified by more than one element in a second language. The genetic code is degenerate because some amino acids are specified by more than one codon.

Answer 9

degenerate code

Question 10

A set of multiple codons that specify the same amino acid

Answer 10

codon family

Question 11

The base at the 5′ end of an anticodon, which pairs loosely and can form mispairs with the base at the 3′ end of the codon.

Answer 11

wobble base

Question 12

The first position of the anticodon, at the 5′ end, which may contain a wobble base.

Answer 12

wobble position

Question 13

A hypothesis proposed by Francis Crick in 1966 to describe how some anticodons can recognize more than one codon.

Answer 13

wobble hypothesis

Question 14

A contiguous, nonoverlapping set of three-nucleotide codons in DNA or RNA.

Answer 14

reading frame

Question 15

AUG (sometimes GUG or, even more rarely, UUG in bacteria and archaea); codes for the first amino acid in a polypeptide sequence: N-formylmethionine in bacteria; methionine in archaea and eukaryotes. Also called a start codon.

Answer 15

initiation/start codon

Question 16

UAA, UAG, and UGA; in protein synthesis, these codons signal the termination of a polypeptide chain. Also called stop codons

Answer 16

termination/stop codons

Question 17

A group of contiguous nonoverlapping nucleotide codons in a DNA or RNA molecule that does not include a termination codon.

Answer 17

open reading frame (ORF):

Question 18

A single-nucleotide change in a gene that results in an amino acid change in the protein product.

Answer 18

missense mutation

Question 19

A mutation in a gene that causes no detectable change in the peptide sequence of the gene product.

Answer 19

silent mutation

Question 20

A point mutation resulting in the exchange of one purine-pyrimidine base pair for another purine-pyrimidine pair. Compare transversion mutation.

Answer 20

transition mutation

Question 21

A mutation that results in the premature termination of a polypeptide chain.

Answer 21

nonsense mutation

Question 22

A mutant tRNA that binds to a termination codon but carries an amino acyl residue that can be incorporated into the growing amino acid chain, suppressing the termination signal.

Answer 22

suppressor tRNA

Question 23

The use of certain degenerate codons more than others to code for a given amino acid.

Answer 23

codon bias