Chapter 4

How many water molecules would be produced in making a polypeptide that is 14 amino acids long?

13

Suppose that codons consisted of 4 nucleotides instead of 3 and that there were only 2 different bases. How many amino acids could be encoded by this variant of the genetic code?

16

How many water molecules would be produced in making a polypeptide that is 20 amino acids long?

19

How many different mRNA sequences could encode the amino acid sequence Ser-Leu-Ser-Arg

216

How many different mRNA sequences could encode the amino acid sequence Met-Leu-Val-His?

48

Which force can contribute to a protein's tertiary structure?

All: Covalent bonding, hydrogen bonding, van der Waal's forces, and ionic bonding

Which step occurs in the A site of the ribosome during translation?

An incoming charged tRNA binds to this site

At physiological pH, the ionized state of the amino (NH2) group in the R group of lysine is:

NH3+.

Which amino acid has its R group covalently linked to the amino group?

Proline

When we say that tRNAs move from the A to P to E sites of a ribosome, what is moving?

The ribosome

One hypothesis for the original function of precursors of tRNA is that:

They carried nucleotides to a self-replicating RNA

Amino acids with hydrophobic R groups are most often found in the interior of folded proteins.

True

Folding domains in proteins encoded in pseudogenes will gradually lose their identity as amino acid replacements take place in the molecule

True

In a protein-coding region, a mutation that replaces a single nucleotide for another may or may not change the resulting amino acid

True

Multiple ribosomes can be simultaneously translating protein from a single mRNA in a eukaryote, but the mRNAs being translated are monocistronic.

True

Which one is responsible for the addition of amino acids after translation initiation has begun?

elongation factors

Which of the environmental factors affect the interactions between amino acids that in turn determine the shape of a protein.

temperature

A polycistronic mRNA with six protein-coding genes has:

6 start codons and 6 stop codons.

A mutation takes place in a protein-coding gene that changes one codon resulting in a single amino acid replacement. Which type of replacement is LEAST likely to result in a disruption of protein structure and function?

A polar amino acid to a polar amino acid

Proteins can be used for which cellular roles?

All: Cell signaling, structural support, biological catalysis, and cell communication

Which factors are used during translation?

All: Elongation factors, release factors, initiation factors

Which of the codons is capable of terminating translation?

All: UAG, UAA, and UGA

Which statements are the steps in the elongation phase of translation?

All: introduction of a charged tRNA into an unoccupied A site of the ribosome, ejection of an uncharged tRNA from the E site of the ribosome, peptide bond formation, and movement of the ribosomes three bases closer to the 3' end of the mRNA

Which step occurs in the E site of the ribosome during translation?

An uncharged tRNA is ejected from this site as the ribosome slides to the next codon.

At physiological pH, the ionized state of the carboxyl (COOH) group in the R group of aspartic acid is:

COO-.

Proteins that do not refold properly after being heated generally require the assistance of which type of molecules in cells?

Chaperones

Because there are three different possible reading frames in a messenger RNA (mRNA) molecule, most mRNAs can be translated in a cell into three different proteins.

False

In a protein-coding region of DNA, any mutation that replaces a single nucleotide for another will replace any amino acid with any other amino acid.

False

Two major types of protein secondary structures are referred to as:

Helix and Sheet

Secondary structure is characterized by which type of interactions?

Hydrogen bonding within the peptide backbone

Refer to the table. Which of the amino acid(s) are encoded by just one codon?

Methionine and Tryptophan

Pseudogenes are relics of former genes that no longer possess biological functions. What would you expect to be the rate at which mutations accumulate in a pseudogene over time compared to the original functional gene?

Mutations will accumulate faster in a pseudogene than in the functional gene

The genetic code is:

Redundant

One hypothesis for the original function of precursors of charged tRNA is that:

The amino acids increased the accuracy of RNA self-replication

One hypothesis for the original function of precursors of charged tRNA is that:

The amino aids increased the accuracy of RNA self-replication

In what order does a charged tRNA move through the sites of a ribosome?

The tRNA binds with the A site, then is moved to the P site, then the E site as the ribosome shifts.

Which step occurs in the P site of the ribosome during translation?

The tRNA carrying the growing polypeptide moves to this site as the ribosome slides to the next codon

Which of the cellular processes occurs in the cytoplasm of a eukaryote?

Translation

Peptide bond formation is catalyzed by the enzymatic activity of an RNA molecule

True

Proteins that evolve extremely rapidly are often difficult to group into families according to their level of sequence similarity.

True

The individual polypeptide chains in a multi-subunit protein each have their own primary, secondary, and tertiary structure.

True

After translation has been initiated, how long will elongation continue?

Until the ribosomes reaches a UAA, UAG, or UGA codon

A mutation takes place in a protein-coding gene that changes one codon resulting in a single amino acid replacement. Which type of replacement is most likely to result in a disruption of protein structure and function?

a hydrophobic amino acid to a hydrophilic amino acid

In eukaryotes, the AUG codon that starts translation is:

adjacent to a Shine-Dalgarno sequence.

Which location is a critical region of a tRNA molecule?

amino acid attachment site and anticodon loop

Which amino acid is most likely to participate in hydrogen bonding with water?

asparagine

In a protein-coding region of DNA, a mutation that replaces a single nucleotide, but does not change the resulting amino acid, is likely to be:

at the 3' position in a codon of the transcribed mRNA

The growing polypeptide remains in the P site throughout translation.

false

When a charged tRNA is about to bind to the vacant A site of a ribosome, where is the growing polypeptide?

in the P site

Transcripts of rRNA genes are concentrated in the:

nucleolus.

Refer to the table. Which amino acids are encoded by the greatest number of codons?

serine and leucine

Ribosomes in prokaryotes and eukaryotes are:

similar in structure and translate using the same genetic codes.

The molecule currently being investigated by researchers as a possible means of synthesis of the first proteins is:

tRNA.

In which of the ribosomal sites does the anticodon of a tRNA pair completely with the mRNA codon?

the A site and the P site

When a peptide bond is created between two amino acids:

the carboxyl group of the first amino acid is joined to the amino group of the second.

A peptide bond between two amino acids is catalyzed by:

the rRNA component of the large subunit of a ribosome.