Biology Chapter 12: Protein Synthesis
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Questions and Answers

What is the first step in the transcription process?

  • RNA polymerase binds to the promoter sequence. (correct)
  • The terminator sequence is reached.
  • RNA is synthesized by complementary base pairing.
  • DNA unwinds at the beginning of a gene.

Which strand of DNA is transcribed during transcription?

  • The coding strand
  • The sense strand
  • Both DNA strands
  • The anti-sense strand (correct)

In what direction does transcription occur?

  • 3' to 3'
  • 3' to 5'
  • 5' to 3' (correct)
  • 5' to 5'

What happens when RNA polymerase reaches the terminator sequence?

<p>Transcription stops. (D)</p> Signup and view all the answers

What does polycistronic mRNA mean?

<p>It contains multiple coding sequences for different proteins. (D)</p> Signup and view all the answers

During the process of transcription, what occurs at the site of synthesis?

<p>DNA that has been transcribed rewinds. (A)</p> Signup and view all the answers

How does RNA polymerase synthesize RNA?

<p>By adding free nucleotides through complementary base pairing. (C)</p> Signup and view all the answers

What is the role of the ribosomal binding site (RBS) in translation?

<p>It connects the ribosome to mRNA. (B)</p> Signup and view all the answers

What is the primary outcome of gene expression alterations due to environmental influences?

<p>Resulting in abnormalities (A)</p> Signup and view all the answers

Which statement about transcription is correct?

<p>Transcription occurs in the nucleus. (D)</p> Signup and view all the answers

What is the role of messenger RNA (mRNA) in the process of translation?

<p>To serve as a template for protein synthesis (B)</p> Signup and view all the answers

Which of the following best describes frameshift mutations?

<p>Result from insertion or deletion of nucleotides. (B)</p> Signup and view all the answers

Which component is responsible for initiating transcription?

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

Which statement about the genetic code is accurate?

<p>A single amino acid can correspond to multiple codons. (B)</p> Signup and view all the answers

What is the significance of the start codon in protein synthesis?

<p>It indicates where to start translating mRNA. (A)</p> Signup and view all the answers

What type of mutation results from the deletion of a single nucleotide?

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

What is the primary role of messenger RNA (mRNA) in the protein synthesis process?

<p>To specify the order of amino acids in a protein. (A)</p> Signup and view all the answers

What is the definition of a mutation?

<p>A change in the base sequence of DNA (A)</p> Signup and view all the answers

Which statement accurately contrasts DNA and RNA?

<p>RNA has ribose sugar, whereas DNA has deoxyribose sugar. (C)</p> Signup and view all the answers

How do single-base addition or deletion mutations affect protein products compared to single-base substitutions?

<p>They shift the reading frame, altering subsequent amino acids. (D)</p> Signup and view all the answers

What distinguishes the stability of DNA from that of RNA?

<p>DNA is highly stable in most cells, while RNA is generally much less stable. (C)</p> Signup and view all the answers

Where is ribosomal RNA (rRNA) primarily located?

<p>In ribosomes, which can be found in the cytoplasm. (C)</p> Signup and view all the answers

Why are most genes regulated at the level of transcription?

<p>It minimizes resource utilization by the cell. (A)</p> Signup and view all the answers

What is a downside of transcriptional regulation of gene expression?

<p>It is a relatively slow process for gene expression control. (D)</p> Signup and view all the answers

What type of RNA is primarily responsible for directing the synthesis of proteins?

<p>Messenger RNA (mRNA) (A)</p> Signup and view all the answers

Which of the following statements about the location of RNA is true?

<p>RNA can be found in the mitochondria and cytosol of eukaryotic cells. (A)</p> Signup and view all the answers

Which of the following statements about mutations is false?

<p>All mutations lead to harmful effects. (C)</p> Signup and view all the answers

In terms of their structural composition, what is a key feature of RNA?

<p>RNA consists of a single polynucleotide strand. (C)</p> Signup and view all the answers

Which of the following is NOT a type of RNA involved in protein synthesis?

<p>Nuclear RNA (nRNA) (A)</p> Signup and view all the answers

What role does transfer RNA (tRNA) play in protein synthesis?

<p>It transports the correct amino acid to the ribosome. (A)</p> Signup and view all the answers

What is the first step in the process of transcription?

<p>RNA polymerase binds to the promoter sequence. (B)</p> Signup and view all the answers

During which cellular process are amino acids linked to form proteins?

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

What modification occurs to mRNA after transcription in eukaryotes?

<p>RNA splicing to remove introns. (A)</p> Signup and view all the answers

In what direction does transcription proceed?

<p>5' to 3' (D)</p> Signup and view all the answers

Which strand of DNA is used as the template during transcription?

<p>The anti-sense strand (D)</p> Signup and view all the answers

What is a codon?

<p>A three-base sequence in mRNA. (A)</p> Signup and view all the answers

What happens when RNA polymerase reaches the terminator sequence?

<p>Transcription stops. (A)</p> Signup and view all the answers

What type of RNA is produced during transcription?

<p>mRNA (B)</p> Signup and view all the answers

What is a key characteristic of introns?

<p>They are transcribed into pre-mRNA but spliced out. (B)</p> Signup and view all the answers

Why is the start codon 'AUG' crucial in translation?

<p>It codes for the amino acid methionine. (B)</p> Signup and view all the answers

Which of the following statements about DNA and RNA is true?

<p>DNA is more stable and serves as the genetic information storehouse. (C)</p> Signup and view all the answers

What does the redundancy of the genetic code mean?

<p>Some amino acids are encoded by multiple codons. (C)</p> Signup and view all the answers

What is the primary role of translation in protein synthesis?

<p>To convert mRNA sequences into amino acid chains. (C)</p> Signup and view all the answers

How many possible codons exist in the genetic code?

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

Which of the following statements regarding gene expression is incorrect?

<p>Only genes coding for proteins undergo transcription. (B)</p> Signup and view all the answers

Flashcards

Gene

A DNA sequence copied into RNA, directing protein production.

Protein

Key determinants of an individual's traits, often enzymes.

Transcription

The process of copying DNA into RNA.

RNA

Single-stranded nucleic acid carrying genetic information.

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mRNA

RNA specifying the order of amino acids in a protein.

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rRNA

A ribosome component that links amino acids in protein synthesis.

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DNA vs. RNA

DNA is double-stranded, stores info, stable; RNA is single-stranded, expresses info, less stable.

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Nucleic acid

DNA and RNA are polymers of nucleotides.

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tRNA function

tRNA carries the correct amino acid to the ribosome based on mRNA codons.

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mRNA codon

A three-base sequence in mRNA that codes for a specific amino acid.

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Transcription location

Transcription occurs in the nucleus of a eukaryotic cell.

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RNA polymerase

Enzyme that synthesizes RNA using one DNA strand as a template.

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Transcription direction

Transcription proceeds in the 5' to 3' direction.

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Transcription start

Transcription begins when RNA polymerase binds to the promoter sequence on DNA.

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Translation location

Translation occurs at the ribosomes in the cytoplasm.

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Codon

A three-base sequence on mRNA that specifies an amino acid.

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Protein Synthesis (Translation)

The process of building proteins from amino acids, following the instructions coded in mRNA.

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Ribosomal Binding Site (RBS)

A sequence on mRNA that signals the ribosome where to bind and begin protein synthesis.

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Initial Peptide Bond

The first covalent bond formed between two amino acids during protein synthesis, marking the start of the polypeptide chain.

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Chain Elongation

The process of adding amino acids to the growing polypeptide chain.

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Chain Termination

The process that stops the addition of amino acids to the polypeptide chain.

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Transcription (Prokaryotes)

The process of creating mRNA from a DNA template in prokaryotes.

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mRNA (in Transcription)

The molecule that carries the genetic code from DNA to the ribosome.

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Transcription Steps

Binding to promoter, unwinding DNA, synthesizing RNA, and reaching terminator.

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Transcription

The process of copying DNA into RNA

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Translation

The process of synthesizing proteins from mRNA

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Codon

A 3-base sequence on mRNA that codes for an amino acid.

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Genetic Code

The set of rules that dictate which mRNA codons specify which amino acids.

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Transcription location

Transcription happens in the nucleus of eukaryotic cells

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Translation location

Translation takes place in the cytoplasm at the ribosomes

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Polypeptide

A chain of amino acids that forms a protein

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Frameshift mutation

A mutation that shifts the reading frame of the genetic message

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RNA vs. DNA

RNA is single-stranded, contains ribose and uracil (U); DNA is double-stranded, contains deoxyribose and thymine (T).

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Transcription product

mRNA molecule complementary to a DNA gene sequence.

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Translation product

A polypeptide (protein) chain created from the mRNA sequence.

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Genetic code redundancy

Multiple codons can code for the same amino acid.

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Start Codon

AUG; sets the reading frame for mRNA codons.

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Introns in Genes

Non-coding DNA sequences transcribed but removed during mRNA processing.

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Translation of mRNA

Converting mRNA's base sequence into a protein's amino acid sequence.

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Transcription direction

RNA polymerase travels from 3' to 5' on the template DNA, resulting in a 5' to 3' mRNA molecule.

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Mutation effect

Changes in DNA sequence, possibly harmful or beneficial.

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Frameshift mutation

A mutation that shifts the reading frame affecting subsequent amino acids.

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Transcriptional Regulation

Controlling gene expression by regulating the transcription process to save resources.

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Post-transcriptional Control

Controlling gene expression after transcription which can occur faster than transcription.

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Single-base addition/deletion

Changes protein product more than substitution because it changes the reading frame downstream.

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Study Notes

Overview of Chapter 12

  • The chapter focuses on the process of converting genetic information into proteins.
  • This process involves two main stages: transcription and translation.
  • RNA plays a crucial role in both stages, acting as an intermediary between DNA and proteins.

Transcription

  • Synthesis of a complementary mRNA strand from a DNA template.
  • Begins when RNA polymerase binds to a promoter sequence on DNA.
  • Proceeds in the 5' to 3' direction (anti-sense strand).
  • Stops when RNA polymerase reaches the terminator sequence on DNA.
  • Occurs in the nucleus.
  • RNA polymerase synthesizes RNA using one strand of DNA as a template.

RNA Structure

  • RNA is a polymer of nucleotides, like DNA.
  • RNA is single-stranded.
  • RNA uses ribose sugar instead of deoxyribose.
  • RNA uses uracil (U) instead of thymine (T).

RNA Types and Functions

  • mRNA (messenger RNA): Specifies the order of amino acids in a protein.
  • rRNA (ribosomal RNA): Main component of ribosomes; assists in making covalent bonds between amino acids.
  • tRNA (transfer RNA): Transports the correct amino acid to the ribosome.

Translation

  • Converting a sequence of bases in mRNA to a sequence of amino acids in a protein.
  • Occurs at the ribosomes, which are made up of proteins and rRNA.
  • Codons of mRNA are "read" sequentially.
  • tRNA molecules transport the required amino acids to the ribosome.
    • tRNA molecules have an anticodon that pairs with the codon.
  • Amino acids are joined by peptide bonds.

Key Points from the Chapters

  • Translation of mRNA starts at a sequence called the Shine-Dalgarno sequence.
  • Translation ends at nonsense codons: UAA, UAG, or UGA.
  • 61 sense codons code for the 20 amino acids.
  • The genetic code is highly specific.
  • The genetic code is unambiguous, meaning each codon specifies only one amino acid.
  • The genetic code is redundant, meaning multiple codons can specify the same amino acid.
  • The genetic code is virtually universal.
  • In eukaryotes, mRNA is chemically modified after transcription.

Additional Details/Concepts

  • Transcription in prokaryotes
    • mRNA can be polycistronic
  • Post-transcriptional processing
    • Modifies mRNA, RNA splicing.
  • Mutations
    • Changes in the base sequence of DNA.
    • Single base addition or deletion is likely to alter the protein product more than a single-base substitution.
  • Genetic Code redundancy and the number of codons.
  • Environmental influences on gene expression can alter gene expression and lead to abnormalities, such as cyclopia.
  • RNA-only genes exist to make RNA other than mRNA and have specific functions other than coding proteins.

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Related Documents

Transcription and Translation PDF

Description

This chapter covers the complex process of protein synthesis, focusing on the stages of transcription and translation. Learn about the crucial role of RNA and its various types in converting genetic information into functional proteins. Discover how RNA is synthesized from DNA and its structural differences from DNA.

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