RNA Molecules and Protein Encoding

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Questions and Answers

What is the process of duplicating double-stranded DNA called?

Transcription

Gene Expression

Translation

Replication (correct)

What type of RNA molecule is a component of ribosomes?

Messenger RNA (mRNA)

Transfer RNA (tRNA)

Protein-encoding RNA

Ribosomal RNA (rRNA) (correct)

What is the process of copying the information encoded in DNA into RNA called?

Replication

Transcription (correct)

Protein Synthesis

Gene Expression

Why do cells require mechanisms to regulate gene expression?

Because not all genes are needed at the same time or in equal quantities Signup and view all the answers

What is the result of regulating the synthesis of mRNA molecules?

A rapid change in the levels of protein production Signup and view all the answers

What type of RNA molecule folds into a characteristic three-dimensional structure that plays a role in protein synthesis?

All of the above Signup and view all the answers

What is the term for the process of reading the sequence of nucleotides in mRNA to build a chain of amino acids?

Translation Signup and view all the answers

What is the primary function of ribosomes?

To align and catalyze the formation of peptide bonds between amino acids Signup and view all the answers

How many different proteins can a cell's DNA encode?

Thousands Signup and view all the answers

What does a ribosome recognize on the mRNA molecule?

The points at which protein synthesis should begin Signup and view all the answers

What is the result of a peptide bond formation between two amino acids?

A polypeptide chain is formed Signup and view all the answers

What is the purpose of the ribosome binding site?

To initiate protein synthesis Signup and view all the answers

What is the product of protein synthesis initiated by a ribosome?

A polypeptide chain Signup and view all the answers

What do ribosomes string together to make a polypeptide?

Amino acids Signup and view all the answers

Which of the following enzymes plays a crucial role in relieving the tension caused by unwinding the two strands of the DNA helix?

DNA gyrase Signup and view all the answers

What is the primary function of helicases during DNA replication?

To unwind the DNA helix at the replication fork Signup and view all the answers

What is the direction of DNA synthesis?

59 to 39 Signup and view all the answers

What type of molecule lacks an initiating site and will not be replicated?

DNA molecule without an origin of replication Signup and view all the answers

What is the function of primers in DNA replication?

To provide short stretches of RNA complementary to the exposed templates Signup and view all the answers

Which of the following is NOT an enzyme involved in DNA replication?

RNA polymerase Signup and view all the answers

What is the function of DNA ligase in DNA replication?

To join two DNA fragments together Signup and view all the answers

Which type of chromosomes typically have multiple origin of replication sites?

Archaeal and eukaryotic chromosomes Signup and view all the answers

What is the primary difference between prokaryotic and eukaryotic mRNA?

Eukaryotic mRNA is synthesized in a precursor form, whereas prokaryotic mRNA is not Signup and view all the answers

What is the purpose of the poly A tail in eukaryotic mRNA?

To stabilize the transcript and enhance translation Signup and view all the answers

What is the fate of the pre-mRNA in eukaryotic cells?

It is processed to form mature mRNA Signup and view all the answers

What occurs at the 5' end of the pre-mRNA during processing?

Capping Signup and view all the answers

Why is a deletion of two base pairs likely to have a greater consequence if it occurs in an exon rather than in an intron?

Because exons code for amino acids, while introns do not Signup and view all the answers

What is the purpose of the cap at the 5' end of the pre-mRNA?

To enhance translation and stabilize the transcript Signup and view all the answers

What is the characteristic of eukaryotic mRNA that distinguishes it from prokaryotic mRNA?

Eukaryotic mRNA is monocistronic, while prokaryotic mRNA is polycistronic Signup and view all the answers

What is the result of polyadenylation during eukaryotic mRNA processing?

The cleavage of the transcript at a specific sequence and the addition of adenine derivatives Signup and view all the answers

What is the importance of using the correct reading frame in protein synthesis?

To prevent the formation of faulty proteins Signup and view all the answers

What is the function of the initiating tRNA in protein synthesis?

To recognize the start codon AUG Signup and view all the answers

What is the consequence of not using the correct reading frame in protein synthesis?

The formation of a faulty protein Signup and view all the answers

Which antibiotic interferes with the function of the bacterial 70S ribosome?

All of the above Signup and view all the answers

What is the function of the tRNA that recognizes the mRNA codon CCG?

To carry the amino acid proline Signup and view all the answers

What is the significance of the 'S' in the 30S and 50S subunits of the ribosome?

It stands for 'Svedberg unit', a measure of size Signup and view all the answers

Which amino acid is carried by the initiating tRNA in protein synthesis?

N-formylmethionine (f-Met) Signup and view all the answers

What is the role of the position of the first AUG codon in protein synthesis?

It determines the reading frame used for translation Signup and view all the answers

What is the function of the tRNA molecule in protein synthesis?

To carry a specific amino acid dictated by its anticodon Signup and view all the answers

What is the role of the 'start' codon in protein synthesis?

To initiate translation Signup and view all the answers

What is the result of the sequence of nucleotides in the codon UUA?

Leucine Signup and view all the answers

What is the function of the codon UAA?

To terminate translation Signup and view all the answers

What is the consequence of a mutation that changes the codon AUG to AUA?

The sequence of amino acids will be altered Signup and view all the answers

What is the role of the codon table in protein synthesis?

To correlate codons to amino acids Signup and view all the answers

In which direction does the ribosome move along the mRNA during protein synthesis?

59 to 39 Signup and view all the answers

What does the ribosome present to the cell during protein synthesis?

Each codon in a sequential order Signup and view all the answers

What is the result of the sequence of nucleotides in the codon GCU?

Valine Signup and view all the answers

What is the importance of maintaining the correct reading frame during protein synthesis?

To ensure that the correct amino acid is added to the polypeptide chain Signup and view all the answers

What is the function of the codon CCG in protein synthesis?

To incorporate Proline into the protein Signup and view all the answers

What is the consequence of a mutation that changes the codon UGG to UGA?

The termination of translation will be initiated Signup and view all the answers

What is the result of the ribosome moving along the mRNA during protein synthesis?

A polypeptide chain is formed Signup and view all the answers

What is the role of the anticodon in tRNA?

To pair with the codon on the mRNA Signup and view all the answers

What is the function of the codon in protein synthesis?

To specify an amino acid or a 'stop' signal. Signup and view all the answers

What is the role of the ribosome during protein synthesis?

To translate the genetic code from mRNA to a polypeptide chain Signup and view all the answers

What is the consequence of the ribosome not moving along the mRNA during protein synthesis?

The polypeptide chain is formed incorrectly Signup and view all the answers

What is the result of a codon specifying more than one amino acid?

Degeneracy in the genetic code. Signup and view all the answers

What is the consequence of a codon specifying a 'stop' signal?

The ribosome releases the polypeptide chain. Signup and view all the answers

How many possible reading frames are there in a given sequence of nucleotides in mRNA?

Three Signup and view all the answers

What determines the beginning and end of the coding region in mRNA?

The sequence of nucleotides. Signup and view all the answers

What is the significance of the ribosome-binding site?

It is the site where the ribosome assembles and translation begins. Signup and view all the answers

In which direction does the ribosome move along the mRNA during translation?

5' to 3' Signup and view all the answers

What is the consequence of not using the correct reading frame during protein synthesis?

A non-functional protein is synthesized. Signup and view all the answers

Study Notes

Types of RNA Molecules

There are three functional types of RNA molecules: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)
Each type of RNA is transcribed from different genes and plays a critical role in protein synthesis

RNA Function in Protein Synthesis

mRNA is translated into protein
tRNA and rRNA fold into characteristic three-dimensional structures that each play a role in protein synthesis
Ribosomal RNA is a component of ribosomes, which are the site of protein synthesis

Regulation of Gene Expression

Cells can regulate gene expression by controlling the synthesis of mRNA molecules
Regulating gene expression allows cells to quickly change the levels of protein production

Replication and Transcription

Replication is the process of duplicating double-stranded DNA
Transcription is the process of copying the information encoded in DNA into RNA
DNA gyrase and helicases are enzymes that temporarily break and unwind the DNA helix at the origin of replication
Primases synthesize short stretches of RNA complementary to the exposed templates

Ribosomes and Translation

Ribosomes are translation "machines" that string amino acids together to make a polypeptide
Ribosomes locate key punctuation sequences on the mRNA molecule, such as the start codon
The correct reading frame is crucial for protein synthesis

Transfer RNA (tRNA)

tRNA carries amino acids and recognizes mRNA codons
The anticodon of tRNA dictates the amino acid it carries

Prokaryotic and Eukaryotic Ribosomes

Prokaryotic ribosomes are composed of a 30S subunit and a 50S subunit
Eukaryotic ribosomes differ significantly from prokaryotic ribosomes in several aspects of transcription and translation

Eukaryotic mRNA Processing

Eukaryotic mRNA is synthesized in a precursor form, called pre-mRNA
Pre-mRNA must be processed (altered) during and after transcription to form mature mRNA
Processing involves capping, polyadenylation, and splicing

Intron and Exon

An intron is a segment of DNA that is removed during processing to form mature mRNA
A deletion of two base pairs would have a greater consequence if it occurred in an exon rather than in an intron

Translation Initiation and Termination

Start codon: AUG, typically the first codon after a ribosome-binding site, initiates translation
Stop codon: three codons (UAA, UAG, UGA) that terminate translation, signaling the end of the protein

The Genetic Code

Correlates a codon (series of three nucleotides) to an amino acid
Many amino acids are specified by more than one codon
Example: threonine is specified by four codons (ACU, ACC, ACA, ACG) that differ only in the third nucleotide

Codon Table

First letter: U, C, A, G
Second letter: U, C, A, G
Third letter: U, C, A, G
Corresponding amino acids:
- UUU: Phe (phenylalanine)
- UCU: Ser (serine)
- UAU: Tyr (tyrosine)
- UGU: Cys (cysteine)
- ...and so on

Reading Frames

Translation begins at the start codon and ends at the stop codon
Any given sequence has three possible reading frames, or ways in which triplets can be grouped
If translation begins in the wrong reading frame, a very different, and generally non-functional, protein is synthesized

Ribosome Movement

The ribosome moves along the mRNA in the 5' to 3' direction
Presents each codon in a sequential order for decoding while maintaining the correct reading frame

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Description

This quiz covers the three functional types of RNA molecules, including messenger RNA, ribosomal RNA, and transfer RNA, and their roles in protein encoding and transcription.