Chapter 14 Quiz

If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system with four different nucleotides?

2

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'

Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?

A base deletion near the start of a gene

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?

A base-pair deletion

What is the relationship among DNA, a gene, and a chromosome?

A chromosome contains hundreds of genes, which are composed of DNA.

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

A deletion of two nucleotides

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

A gene from an organism can theoretically be expressed by any other organism.

Which of the following does not occur in prokaryotic gene expression, but does in eukaryotic gene expression?

A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.

Which of the following nucleotide triplets best represents a codon?

A triplet in the same reading frame as an upstream AUG.

A portion of the genetic code is UUU = phenylalanine, GCC = alanine, AAA = lysine, and CCC = proline. Assume the correct code places the amino acids phenylalanine, alanine, and lysine in a protein (in that order). Which of the following DNA sequences would substitute proline for alanine?

AAA-GGG-TTT

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is

AAA.

The nitrogenous base adenine is found in all members of which group?

ATP, RNA, and DNA

What is a ribozyme?

An RNA with enzymatic activity

A mutation results in a defective enzyme a. In the following simple metabolic pathway, what would be a consequence of that mutation? Enzyme A Enzyme B A ⟶ B ⟶ C

An accumulation of A and no production of B and C.

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the

Bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.

Each of the following is a modification of the sentence THECATATETHERAT. A. THERATATETHECAT B. THETACATETHERAT C. THECATARETHERAT D. THECATATTHERAT E. CATATETHERAT Which of the above is analogous to a single substitution mutation?

C

Each of the following is a modification of the sentence THECATATETHERAT. A. THERATATETHECAT B. THETACATETHERAT C. THECATARETHERAT D. THECATATTHERAT E. CATATETHERAT Which of the above is analogous to a frameshift mutation?

D

Which of the following provides some evidence that RNA probably evolved before DNA?

DNA polymerase uses primer, usually made of RNA.

The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true?

If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).

How is the template strand for a particular gene determined?

It depends on the orientation of RNA polymerase, whose position is determined by particular sequences of nucleotides within the promoter.

What is the effect of a nonsense mutation in a gene?

It introduces a premature stop codon into the mRNA.

Why might a point mutation in DNA make a difference in the level of protein's activity?

It might substitute an amino acid in the active site.

Suppose that a mutation alters the formation of a tRNA such that it still attaches to the same amino acid (phe) but its anticodon loop has the sequence AAU that binds to the mRNA codon UUA (that usually specifies leucine leu).

One mutated tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones.

A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following activated transfer RNA molecules are available. Two of them can correctly match the mRNA so that a dipeptide can form. The dipeptide that will form will be

Proline-threonine.

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

Ribosomes and tRNA

In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication?

The entire template molecule is represented in the product.

The TATA sequence is found only several nucleotides away from the start site of transcription. This most probably relates to which of the following?

The number of hydrogen bonds between A and T in DNA.

A biologist inserts a gene from a human liver cell into the chromosome of a bacterium. The bacterium then transcribes this gene into mRNA and translates the mRNA into protein. The protein produced is useless. The biologist extracts the protein and mature mRNA that codes for it. When analyzed you would expect which of the following results?

The protein and the mature mRNA are longer than in human cells.

Which of the following is the first event to take place in translation in eukaryotes?

The small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA

Which of the following variations on translation would be most disadvantageous for a cell?

Translating polypeptides directly from DNA.

This figure represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which of the following triplets of bases on the mRNA strand codes for this amino acid?

UUC