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Which of the following steps occurs last in the initiation phase of translation?
The large ribosomal subunit joins the complex.
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Key Terms
Term
Definition
Which of the following steps occurs last in the initiation phase of translation?
The large ribosomal subunit joins the complex.
At which site do new aminoacyl tRNAs enter the ribosome during elongation?
A-site
What is meant by translocation?
The ribosome slides one codon down the mRNA.
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.
False
Which one of the following is true of tRNAs?
Each tRNA binds a particular amino acid.
How is translation initiated?
The small ribosomal subunit binds to the mRNA. The tRNA bearing methionine binds to the start codon. The large ribosomal subunit binds to the small on...
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| Term | Definition |
|---|---|
Which of the following steps occurs last in the initiation phase of translation? | The large ribosomal subunit joins the complex. |
At which site do new aminoacyl tRNAs enter the ribosome during elongation? | A-site |
What is meant by translocation? | The ribosome slides one codon down the mRNA. |
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated. | False |
Which one of the following is true of tRNAs? | Each tRNA binds a particular amino acid. |
How is translation initiated? | The small ribosomal subunit binds to the mRNA. The tRNA bearing methionine binds to the start codon. The large ribosomal subunit binds to the small one. The start codon signals the start of translation. |
A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is | UUU. |
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. |
There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that | the rules for base pairing between the third base of a codon and tRNA are flexible. |
When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? | an assembled ribosome with a polypeptide attached to the tRNA in the P site |
What is the function of the release factor (RF)? | It binds to the stop codon in the A site in place of a tRNA. |
A part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' (mRNA). The following charged transfer RNA molecules (with their anticodons shown in the 3' to 5' direction) 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. |
What type of bonding is responsible for maintaining the shape of the tRNA molecule? | hydrogen bonding between base pairs |
The figure represents tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid? | UUC |
True or false? A codon is a group of three bases that can specify more than one amino acid. | False |
Which of the following statements about mutations is false? | A knock-out mutation results in a total absence of the mutated protein. |
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred? | Deletion |
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)? | One addition and one deletion mutation. |
If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein? | Two. |
If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred? | An addition mutation and a deletion mutation. |
What does a mutagen cause? | a change in the sequence of DNA |
What is the effect of a nonsense mutation in a gene? | It introduces a premature stop codon into the mRNA. |
A frameshift mutation could result from | either an insertion or a deletion of a base. |
Which of the following DNA mutations is the most likely to be damaging to the protein it specifies? | a base-pair deletion |
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene? | a frameshift deletion at the beginning of the gene |
Of the following, which is the most current description of a gene? | a DNA sequence that is expressed to form a functional product: either RNA or polypeptide |
The process of translation, or protein synthesis, is a crucial part of the maintenance of living organisms. Proteins are constantly in use and will break down eventually, so new ones must always be available. If protein synthesis breaks down or stops, then the organism dies. | This statement emphasizes the importance of continuous protein synthesis for organism survival. |
Which codon on the mRNA strand codes for phenylalanine? | UUC |
What is the function of the release factor (RF) in translation? | It binds to the stop codon in the A site in place of a tRNA. |