Biology Chapter: Protein Synthesis

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Questions and Answers

How many potential combinations of codons are there?

  • 16
  • 128
  • 64 (correct)
  • 4

What is the primary function of the start codon?

  • Codes for the amino acid methionine
  • Signals the end of protein synthesis
  • Initiates the binding of ribosomes to mRNA (correct)
  • Dictates the order of amino acids in a protein

Which of the following statements is TRUE about the genetic code?

  • The genetic code is always read from its 3' end to its 5' end.
  • The genetic code is universal, meaning it is identical across all living organisms.
  • The genetic code is overlapping, meaning that a single nucleotide can be part of multiple codons.
  • The genetic code is commaless, meaning that there are no gaps or punctuation between codons. (correct)

Which of the following is NOT a characteristic of the genetic code?

<p>Ambiguous (D)</p> Signup and view all the answers

If a codon is composed of three nucleotides, and there are four different nucleotides, how many possible codons are there?

<p>64 (C)</p> Signup and view all the answers

What is the name of the process that converts the genetic information in DNA into RNA?

<p>Transcription (C)</p> Signup and view all the answers

Which of the following statements accurately describes the relationship between mRNA, tRNA, and rRNA?

<p>mRNA carries the genetic code from DNA to the ribosomes, tRNA brings amino acids to the ribosomes, and rRNA is a component of the ribosomes. (B)</p> Signup and view all the answers

What type of mutation alters the reading frame of mRNA?

<p>Frameshift mutation (A)</p> Signup and view all the answers

Which of the following is NOT a component required for translation?

<p>DNA (A)</p> Signup and view all the answers

What is the function of tRNA in protein synthesis?

<p>Carries amino acids to the ribosomes (B)</p> Signup and view all the answers

What is the difference between prokaryotic and eukaryotic ribosomes?

<p>Prokaryotic ribosomes have a sedimentation coefficient of 80S, while eukaryotic ribosomes have a sedimentation coefficient of 70S (B)</p> Signup and view all the answers

Which of the following is an example of a frameshift mutation?

<p>UCA UCC UAU GGC U -&gt; UCA UCC UAU GGC UU (A)</p> Signup and view all the answers

What is the role of the 5' UTR and 3' UTR in mRNA?

<p>They are involved in regulating translation and mRNA stability (C)</p> Signup and view all the answers

Why is the genetic code described as degenerate?

<p>Because it is redundant, meaning several codons can code for the same amino acid (B)</p> Signup and view all the answers

Which of the following statements accurately describes the difference between a prokaryotic and eukaryotic cell in relation to protein synthesis?

<p>Transcription and translation occur in the cytoplasm of both prokaryotic and eukaryotic cells, with no nucleus separating them in prokaryotes. (D)</p> Signup and view all the answers

What is the primary role of the pre-mRNA processing step in eukaryotic cells?

<p>To remove introns and add a 5' cap and poly-A tail, which are essential for mRNA stability and translation in the cytoplasm. (A)</p> Signup and view all the answers

Why is translation in prokaryotic cells able to begin while mRNA is still being transcribed?

<p>The lack of a nuclear membrane in prokaryotes enables the ribosome to access the mRNA during transcription. (A)</p> Signup and view all the answers

What is the significance of the nuclear envelope in eukaryotic cells for protein synthesis?

<p>It allows for post-transcriptional modifications of the pre-mRNA, ensuring the production of functional mRNA that can be transported for translation. (D)</p> Signup and view all the answers

Which of the following accurately describes the role of the ribosome in protein synthesis?

<p>The ribosome reads the mRNA and uses it to assemble amino acids into a polypeptide chain. (C)</p> Signup and view all the answers

What is the difference between a prokaryotic and eukaryotic gene?

<p>Prokaryotic genes are organized in operons, while eukaryotic genes are not. (D)</p> Signup and view all the answers

Why is the order of events in protein synthesis important?

<p>It ensures the production of the right protein by linking specific amino acids in the correct order. (D)</p> Signup and view all the answers

Why is pre-mRNA processing necessary in eukaryotic cells?

<p>To allow for the removal of non-coding sequences (introns) and for the addition of 5' cap and 3' poly-A tail, increasing mRNA stability and translation efficiency. (A)</p> Signup and view all the answers

Flashcards

Protein Synthesis

The process through which cells create proteins based on genetic information.

Transcription

The process of creating mRNA from DNA in the nucleus.

Translation

The process of converting mRNA into a polypeptide chain of amino acids.

Prokaryotic Cells

Cells without a nucleus where transcription and translation occur simultaneously.

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Eukaryotic Cells

Cells with a nucleus that separate transcription and translation processes.

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Pre-mRNA

The initial RNA transcript that must be processed before becoming mature mRNA.

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RNA Processing

The modifications made to pre-mRNA before it becomes mature mRNA, including capping and splicing.

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Mature mRNA

The processed form of mRNA that exits the nucleus to be translated into protein.

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Central Dogma

The flow of genetic information from DNA to RNA to protein.

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Genetic Code

A dictionary that translates sequences of nucleotide bases into amino acids.

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Codon

A sequence of three nucleotide bases in mRNA that codes for an amino acid.

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Start Codon

The specific codon (AUG) that signals the beginning of protein synthesis.

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Termination Codons

Codons (UAG, UGA, UAA) that signal the end of protein synthesis.

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Degenerate Code

Phenomenon where a single amino acid can be encoded by multiple codons.

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Non-overlapping Code

Genetic code is read in a continuous sequence of triplets without overlap.

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Frameshift Mutation

A genetic mutation caused by insertions or deletions that alter the reading frame of mRNA.

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Types of RNA

Includes mRNA, rRNA, and tRNA, each serving distinct roles in protein synthesis.

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mRNA

Messenger RNA that carries genetic information from DNA to ribosomes.

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rRNA

Ribosomal RNA that makes up the ribosome and aids in protein synthesis.

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tRNA

Transfer RNA that brings amino acids to the ribosome during translation.

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Ribosome

The cellular machinery that synthesizes proteins by translating mRNA.

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Study Notes

Protein Synthesis

  • Protein synthesis involves transcription and translation
  • Prokaryotes lack a nucleus, so transcription and translation occur simultaneously in the cytoplasm
  • Eukaryotes have a nucleus, so transcription occurs in the nucleus, and the mRNA is processed before translation in the cytoplasm

Transcription

  • Transcription is the process of creating mRNA from DNA
  • In prokaryotes, the mRNA produced is directly translated
  • In eukaryotes, a pre-mRNA is produced which is processed before leaving the nucleus as mRNA

Translation

  • Translation is the decoding of mRNA to produce a polypeptide chain (protein)
  • The genetic code is a dictionary that matches sequences of bases to specific amino acids
  • A codon is a three-nucleotide sequence on mRNA that codes for a particular amino acid. There are 64 possible codons.
  • The start codon is AUG and codes for methionine
  • There are three stop codons (UAG, UGA, and UAA) that signal the end of translation
  • Translation requires mRNA, tRNA, amino acids, ribosomes, and various protein factors
  • Ribosomes are complex structures containing rRNA and proteins. They are responsible for polypeptide synthesis. They have two main subunits, and these work together to decode mRNA and synthesize proteins.

Components of Protein Synthesis

  • Amino acids: building blocks of proteins
  • mRNA: carries genetic information from DNA to ribosomes
  • tRNA: carries amino acids to ribosomes
  • Ribosomes: site of protein synthesis
  • Protein factors: various proteins required for translation
  • ATP and GTP: provide energy for translation
  • Aminoacyl tRNA synthetases: enzymes that attach amino acids to tRNA molecules

Types of RNA

  • Messenger RNA (mRNA): Carries genetic information from DNA to ribosomes
  • Transfer RNA (tRNA): Carries amino acids to ribosomes
  • Ribosomal RNA (rRNA): Component of ribosomes, directly involved in polypeptide synthesis

Prokaryotic vs Eukaryotic Protein Synthesis

  • Prokaryotes: Simultaneous transcription and translation in the cytoplasm
  • Eukaryotes: Transcription in the nucleus, mRNA processing, and then translation in the cytoplasm

Characteristics of the Genetic Code

  • Specific: Each codon specifies a particular amino acid or stop signal
  • Universal: Nearly universal across all organisms
  • Degenerate (redundant): Multiple codons can code for the same amino acid
  • Non-overlapping and commaless: the code is read continuously without punctuation marks

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