Question 1

Which mutation is least likely to cause a frame shift?

Accepted Answer

Mutations that add or remove nucleotides in multiples of three (like 6 or 14) are least likely to cause a frameshift because they do not disrupt the triplet reading frame of the genetic code.

Question 2

The three-dimensional structure of tRNA is maintained by

Accepted Answer

The three-dimensional structure of tRNA is maintained by hydrogen bonds between complementary base pairs, as well as between the bases and the sugar-phosphate backbone of the molecule. Peptide bonds connect the amino acids in a protein, disulfide bridges form between cysteine residues in proteins, phosphodiester bonds connect nucleotides in a nucleic acid strand, and glycosidic linkages connect monosaccharides in a carbohydrate. None of these are directly involved in maintaining the structure of tRNA.

Question 3

Which statement about the 5' cap of mRNA is false?

Accepted Answer

The answer of Which statement about the 5' cap of...

Question 4

The anticodon 3'-AUC-5' would pair with the codon

Accepted Answer

The answer of The anticodon 3'-AUC-5' would pair with the...

Question 5

Use the following to answer questions :
Suppose a gene has three exons,with 570 nucleotides in exon 1,420 in exon 2,and 810 in exon 3.
-The protein translated from this gene is _______ amino acids long.

Accepted Answer

The answer of Use the following to answer questions :
Suppose...

Question 6

Suppose that a certain mRNA is transcribed at a normal rate in the nucleus,but it is found at very low levels in the cytoplasm.Which of the following would be the most plausible explanation for this phenomenon?

Accepted Answer

The addition of the poly A tail to pre-mRNA is necessary for transport of the mRNA from the nucleus to the cytoplasm. Without it, the mRNA cannot be exported to the cytoplasm for translation, resulting in low levels of the mRNA in the cytoplasm.

Question 7

The anticodon 3'-GCI-5'could not pair with

Accepted Answer

The anticodon 3'-GCI-5' can pair with codons 5'-GCA-3', 5'-GCU-3', and 5'-GCC-3' due to wobble base pairing, but not with 5'-GCG-3' because 'I' (inosine) cannot pair with 'G'.

Question 8

Which statement best illustrates the concept that the genetic code is redundant?

Accepted Answer

The statement that codons CCU and CCC both code for the same amino acid, proline, shows the redundancy of the genetic code. Different codons can code for the same amino acid, providing redundancy in the code.

Question 9

In order to examine which molecule is recognized by the protein synthesis machinery,Seymour Benzer

Accepted Answer

The answer of In order to examine which molecule is...

Question 10

UGU and UGC both code for cysteine.A change from UGU to UGC would thus be a(n)_______ mutation.

Accepted Answer

A silent mutation is a change in the nucleotide sequence that does not alter the amino acid sequence of the protein, as both UGU and UGC code for cysteine.

Question 11

Imagine that a novel life form is found deep within Earth's crust.It uses DNA as an information storage molecule,and transcription and translation occur as in other life forms with one exception: a codon for this organism is just two bases in length.What is the maximum number of different amino acids that could be encoded from such a genetic code?

Accepted Answer

In standard genetic code, there are 64 possible codons (4 bases in length, and 3 possible bases in each position). However, if a codon for this novel life form is just two bases in length, there are only 16 possible codons (4 possible bases in each position). Since each codon can encode for one of the 20 standard amino acids, the maximum number of different amino acids that could be encoded from such a genetic code is 16. Therefore, the correct answer is B) 16.

Question 12

Which statement about the genetic code is true?

Accepted Answer

The genetic code is believed to have evolved in the common ancestor of all known life. Studies suggest that there are no significant differences in the genetic code used by eukaryotes, archaea, and bacteria, indicating that it was established before the diversification of these domains of life.

Question 13

Which statement about tRNAs is false?

Accepted Answer

During elongation, the anticodon of an incoming tRNA first binds to the codon at the A site, not the P site.

Question 14

Use the following to answer questions :
Suppose a gene has three exons,with 570 nucleotides in exon 1,420 in exon 2,and 810 in exon 3.
-Now suppose there is a variant in which exon 2 is also spliced out from the mature mRNA.The protein translated from this genetic variant is _______ amino acids long.

Accepted Answer

The answer of Use the following to answer questions :
Suppose...

Question 15

Which finding would be the most plausible?

Accepted Answer

Pre-RNA (or precursor mRNA) is longer than mature mRNA because it contains introns, which are non-coding regions that are spliced out during RNA processing to form the mature mRNA.

Question 16

How many codons encode amino acids?

Accepted Answer

There are 64 possible codons, but 3 of them (UAA, UAG, UGA) are stop codons and do not encode any amino acids. Therefore, the number of codons that encode amino acids is 61.

Question 17

The three codons in the genetic code that do not specify amino acids are called

Accepted Answer

The three codons that do not specify amino acids are known as stop codons (UAA, UAG, and UGA). They signal the termination of protein synthesis during translation.

Question 18

An mRNA molecule with 360 codons has _______ nucleotides.

Accepted Answer

Each codon is made up of 3 nucleotides, so the total number of nucleotides in an mRNA molecule can be found by multiplying the number of codons by 3. Therefore, 360 codons would have 360 x 3 = 1,080 nucleotides. Hence, the correct answer is D.

Question 19

Which change affects one and only one amino acid in a sequence?

Accepted Answer

A missense mutation is a type of point mutation where a single nucleotide change results in a different amino acid being encoded. This affects only one amino acid in the sequence. A silent mutation and a nonsense mutation may also result from a single nucleotide change, but they do not always result in a change of the encoded amino acid. A deletion mutation and a frame-shift mutation may affect multiple amino acids in the sequence.

Question 20

The "wobble" phenomenon refers to a lack of specificity between the _______ end of the codon and the _______ end of the anticodon.

Accepted Answer

The "wobble" phenomenon refers to the flexibility in base pairing between the 3' end of the codon and the 5' end of the anticodon, allowing for some variation in the third base pair.

Quiz 10: From Dna to Protein: Gene Expression