Q: Which codons are used as termination signals in the genetic code?

$$\text{UAA}$$, $$\text{UAG}$$, $$\text{UGA}$$

Question 1

Which property of the genetic code ensures that each codon specifies only one amino acid or stop signal?

Accepted Answer

The code is unambiguous

Question 2

A frameshift mutation occurs when one or two nucleotides are inserted or deleted from a coding sequence. What is the effect of a frameshift mutation on the reading frame?

Accepted Answer

It changes the reading frame, altering all downstream codons

Question 3

Which codon is used as the start signal for translation in eukaryotes?

Accepted Answer

$$	ext{AUG}$$

Question 4

In the triplet binding assay, what is the role of the ribosome?

Accepted Answer

It binds the triplet mRNA and the appropriate charged tRNA, allowing identification of the codon

Question 5

If a synthetic mRNA is composed entirely of poly-U, which amino acid will be incorporated into the protein?

Accepted Answer

Phenylalanine

Question 6

What is the probability of the codon $$	ext{CCC}$$ occurring in a synthetic mRNA made with a 1A:5C ratio of ribonucleotides?

Accepted Answer

$$\left(\frac{5}{6}\$$right)^3$$ = 57.9\%$$

Question 7

Which feature of the genetic code allows a single tRNA to recognize multiple codons?

Accepted Answer

The wobble hypothesis

Question 8

Why are mutations in the third position of a codon less likely to affect protein function?

Accepted Answer

The third position is less spatially constrained, allowing for wobble pairing

Question 9

Which amino acid is specified by only one codon in the genetic code?

Accepted Answer

Methionine

Question 10

A mutation changes the first base of a codon specifying a hydrophobic amino acid. What is the likely outcome?

Accepted Answer

The new codon will likely specify another hydrophobic amino acid

Question 11

Which experiment provided early evidence that the genetic code is a triplet code?

Accepted Answer

Frameshift mutation studies in viruses

Question 12

What is the main function of polynucleotide phosphorylase in deciphering the genetic code?

Accepted Answer

It synthesizes RNA without a template, allowing creation of synthetic mRNAs

Question 13

Which codons are used as termination signals in the genetic code?

Accepted Answer

$$	ext{UAA}$$, $$	ext{UAG}$$, $$	ext{UGA}$$

Question 14

In a cell-free protein synthesis system, what is the purpose of using a radiolabeled amino acid?

Accepted Answer

To detect which amino acid is incorporated into the protein

Question 15

Which property of the genetic code helps buffer the effects of mutations on protein function?

Accepted Answer

Ordered nature of the code

Question 16

If a mutation changes a codon from $$	ext{UGU} to$$ $$	ext{UGC}$$, what is the effect on the protein?

Accepted Answer

No effect, both codons specify cysteine

Question 17

Why is the genetic code described as nearly universal?

Accepted Answer

It is conserved in almost all organisms, with minor exceptions

Question 18

What is colinearity in the context of the genetic code?

Accepted Answer

The linear sequence of codons in a gene corresponds precisely with the linear amino acid sequence of the protein

Question 19

In the triplet binding assay, which component is radiolabeled to detect codon assignment?

Accepted Answer

Amino acid

Question 20

Which codon would most likely be found at the N-terminus of a newly synthesized eukaryotic protein?

Accepted Answer

$$	ext{AUG}$$

The Genetic Code and Transcription: Deciphering the Flow of Genetic Information

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