Biology Chapter: Protein Synthesis

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Questions and Answers

How many potential combinations of codons are there?

128

64 (correct)

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?

Ambiguous (D) 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?

64 (C) Signup and view all the answers

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

Transcription (C) Signup and view all the answers

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

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) Signup and view all the answers

What type of mutation alters the reading frame of mRNA?

Frameshift mutation (A) Signup and view all the answers

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

DNA (A) Signup and view all the answers

What is the function of tRNA in protein synthesis?

Carries amino acids to the ribosomes (B) Signup and view all the answers

What is the difference between prokaryotic and eukaryotic ribosomes?

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

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

UCA UCC UAU GGC U -> UCA UCC UAU GGC UU (A) Signup and view all the answers

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

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

Why is the genetic code described as degenerate?

Because it is redundant, meaning several codons can code for the same amino acid (B) 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?

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

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

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

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

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

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

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

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

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

What is the difference between a prokaryotic and eukaryotic gene?

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

Why is the order of events in protein synthesis important?

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

Why is pre-mRNA processing necessary in eukaryotic cells?

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) Signup and view all the answers

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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Description

This quiz covers the essential processes of protein synthesis, including transcription and translation. It highlights the differences between prokaryotic and eukaryotic mechanisms, the creation of mRNA from DNA, and the decoding of mRNA into proteins. Test your knowledge on codons, genetic codes, and the overall process of protein synthesis.