Ch 11 From DNA to Proteins: Translation

Question 1

one-gene, one-enzyme hypothesis

Answer 1

Beadle and Tatum developed this which suggested that genes function by encoding enzymes and that each gene encodes a separate enzyme

Question 2

one-gene, one-polypeptide hypothesis

Answer 2

some proteins are composed of more than one polypeptide chain and that different polypeptide chains are encoded by separate genes

Question 3

amino acids

Answer 3

all proteins are polymers composed of these linked end to end
each consists of a central carbon atom bonded to an amino group, a hydrogen atom, a carboxyl group, and an R (radical) group that differs for each amino acid

Question 4

peptide bonds

Answer 4

amino acids in proteins are joined together by these to form polypeptide chains; a protein consists of one or more polypeptide chains

Question 5

polypeptide

Answer 5

have polarity: one end has a free amino group (NH3+) and the other end has a free carboxyl group (COO-)

Question 6

two common secondary structures found in proteins

Answer 6

beta pleated sheet and the alpha helix

Question 7

polynucleotide phosphorylase

Answer 7

does not require a template

it randomly links together any RNA nucleotides that happen to be available

Question 8

sense codons

Answer 8

61 codons encode amino acids

Question 9

degenerate

Answer 9

amino acids may be specified by more than one codon

Question 10

synonymous codons

Answer 10

codons that specify the same amino acid

Question 11

isoaccepting tRNAs

Answer 11

different tRNAs that accept the same amino acid but have different anticodons

Question 12

wobble

Answer 12

when bases pair weakly, may be flexibility

the hypothesis proposed that there could be some nonstandard pairings of bases at the third position of a codon

Question 13

nonoverlapping

Answer 13

each nucleotide is a part of a single codon

Question 14

reading frame

Answer 14

each different way of reading the sequence and any sequence of nucleotides has three potential reading frames

Question 15

initiation (start codon)

Answer 15

the reading frame is set by this which is the first codon of the mRNA to specify an amino acid

Question 16

stop codons, termination codons, nonsense codons

Answer 16

UAA, UAG, and UGA signal the end of the protein in both bacterial and eukaryotic cells

Question 17

universal

Answer 17

genetic code was assumed to be this meaning that each codon specifies the same amino acid in all organisms

Question 18

aminoacyl-tRNA synthetases

Answer 18

the key to specificity between an amino acid and its tRNA is a set of enzymes
each recognizes a particular amino acid as well as all the tRNAs that accept that amino acid

Question 19

tRNA charging

Answer 19

attachment of a tRNA to its appropriate amino acid, requires energy which is supplied by adenosine triphosphate (ATP)

Question 20

initiation factor 3 (IF-3)

Answer 20

binds to the small subunit of the ribosome and prevents the large subunit from binding during initiatioin

Question 21

initiation factor 1 (IF-1)

Answer 21

enhances the disassociation of the large and small ribosomal subunits

Question 22

initiation factor 2 (IF-2)

Answer 22

required for the attachment between initiator tRNA and the initiation codon

Question 23

30S initiation complex

Answer 23

complex consisting of 1) the small subunit of the ribosome, 2) the mRNA, 3) the initiator tRNA with its amino acid, 4) one molecule of GTP, and 5) several initiation factors

Question 24

70S initiation complex

Answer 24

when the large subunit has joined the initiation complex

Question 25

Kozak sequence

Answer 25

the identification of the start codon is facilitated by the presence of a consensus sequence that surrounds the start codon

Question 26

a ribosome has three sites that can be occupied by tRNAs

Answer 26

the aminoacyl (A) site, the peptidyl (P) site, and the exit (E) site

Question 27

elongation factor Tu (EF-Tu)

Answer 27

a charged tRNA binds to the A site; binding takes place when this joins with GTP and then with a charged tRNA to form a three-part complex

Question 28

elongation factor Ts (EF-Ts)

Answer 28

regenerates EF-Tu-GTP from EF-Tu-GDP

Question 29

translocation

Answer 29

third step in elongation

the movement of the ribosome down the mRNA in the 5’-3’ direction

Question 30

elongation factor G (EF-G)

Answer 30

translocation positions the ribosome over the next codon and requires this

Question 31

release factors

Answer 31

bind to the ribosome

E. coli has three release factors: RF-1, RF-2, and RF-3

Question 32

polyribosome

Answer 32

an mRNA with several ribosomes attached; often just a polysome

Question 33

molecular chaperones

Answer 33

correct folding may initially require the participation of other molecules