Biology Chapter on Protein Synthesis
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Questions and Answers

What is the first step in the elongation stage of protein synthesis?

  • The empty tRNA is released from the ribosome from the E site.
  • Met-tRNA (initiator tRNA) is bound to the P site. The A site is empty. (correct)
  • The ribosome moves along the mRNA to the next codon.
  • The second tRNA, with an appropriate anticodon and amino acid (AA2), binds to the codon in the A site of the ribosome.

The codon UAA is a stop codon.

True (A)

What is the name of the enzyme that catalyzes the formation of a peptide bond between amino acids during protein synthesis?

peptidyl transferase

A permanent change in the nucleotide sequence of a cell’s DNA is called a ______.

<p>mutation</p> Signup and view all the answers

Match the following types of mutations with their descriptions:

<p>Point mutation = A change in a single nucleotide within a gene Chromosomal mutation = A large-scale mutation that may affect multiple genes Deletion = The removal of one or more nucleotides from a gene Insertion = The addition of one or more nucleotides to a gene Substitution = The replacement of one nucleotide with another in a gene Inversion = A segment of DNA is reversed within a chromosome Translocation = A segment of DNA is moved from one chromosome to another Duplication = A segment of DNA is copied and inserted into a chromosome</p> Signup and view all the answers

Which of the following is NOT a stop codon?

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

What is the role of a protein release factor in protein synthesis?

<p>To bind to a stop codon in the A site and release the polypeptide chain from the tRNA at the P site.</p> Signup and view all the answers

Mutagens are agents that cause an increase in the rate of mutations.

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

Given a DNA sequence of 5’-CCTAGAA-3’, what would the complementary strand read?

<p>3’ GGATCTT 5’ (B)</p> Signup and view all the answers

The leading and lagging strands during DNA replication are identical copies of each other.

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

What is the primary purpose of DNA transcription within a cell?

<p>To convert DNA to RNA</p> Signup and view all the answers

During protein synthesis, DNA must first be converted to ______.

<p>RNA</p> Signup and view all the answers

Which of the following best describes the role of hemoglobin?

<p>Transport of oxygen (C)</p> Signup and view all the answers

Match the following types of proteins with their function:

<p>Myosin = Muscular contraction Insulin = Hormonal regulation Immunoglobulin = Protection Keratin = Structural support</p> Signup and view all the answers

When cells need a particular protein, they need to produce thousands or even _______ of copies.

<p>millions</p> Signup and view all the answers

If a leading strand has the sequence 5’-CGCATGTAGCGA-3’, what is the sequence of the complementary parent strand?

<p>3’-GCGTACATCGCT-5’ (A)</p> Signup and view all the answers

If a leading strand has the sequence 5’-CGCATGTAGCGA-3’, what is the sequence of the lagging strand sequence?

<p>3’-GCGTACATCGCT-5’ (D)</p> Signup and view all the answers

Which molecule acts as an intermediary between DNA and the ribosomes?

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

Transcription ends when RNA polymerase does not recognize a termination sequence.

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

What is the function of tRNA?

<p>Transfer RNA (tRNA) delivers amino acids to ribosomes during protein synthesis.</p> Signup and view all the answers

Which of these is NOT directly involved in the process of transcription?

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

Ribosomal RNA (rRNA) bind with ________ to form the ribosomes.

<p>proteins</p> Signup and view all the answers

Match the following RNA types with their function:

<p>mRNA = Carries genetic code from DNA to ribosomes tRNA = Delivers amino acids to ribosomes rRNA = Forms the structure of ribosomes</p> Signup and view all the answers

Pre-mRNA is ready to leave the nucleus immediately after being synthesized.

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

Which of the following is a key difference between DNA and RNA?

<p>DNA contains deoxyribose sugar, while RNA contains ribose sugar. (B)</p> Signup and view all the answers

RNA polymerase requires a primer to begin transcription.

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

What is the function of the promoter in transcription?

<p>The promoter is a nucleotide sequence that allows for the binding of RNA polymerase to begin transcription.</p> Signup and view all the answers

In RNA, adenine pairs with ______.

<p>uracil</p> Signup and view all the answers

Match the following terms with their description.

<p>Transcription = The process of copying DNA into RNA. Promoter = A nucleotide sequence located just before a gene where RNA polymerase binds. Coding Strand = The DNA strand that has the same sequence as the new RNA molecule. RNA Polymerase = The enzyme responsible for building the RNA molecule during transcription.</p> Signup and view all the answers

In which direction is the new RNA molecule synthesized?

<p>5' → 3' (C)</p> Signup and view all the answers

The coding strand of DNA is used as the template for RNA synthesis.

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

Why do promoters often have A-T rich sequences?

<p>A-T base pairs have only two hydrogen bonds, requiring less energy for RNA polymerase to open the DNA.</p> Signup and view all the answers

What is the purpose of the 3' poly(A) tail added to pre-mRNA?

<p>To protect from enzymes in the cytosol (C)</p> Signup and view all the answers

Introns are coding sequences of DNA or RNA.

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

What is the main function of a spliceosome?

<p>To remove introns from mRNA.</p> Signup and view all the answers

The sequence that helps ribosomes recognize the initial attachment site on mRNA is called the 5' ______.

<p>cap</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Codon = Three consecutive nucleotides that correspond to an amino acid Anticodon = The complementary base pair sequence on a tRNA Exon = Coding sequence of a gene Intron = Non-coding sequence of a gene</p> Signup and view all the answers

Alternative splicing allows for the production of:

<p>Multiple proteins from a single gene (C)</p> Signup and view all the answers

TRNA molecules are typically long sequences of 500-1000 nucleotides.

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

What does the term 'spliceosome' refer to?

<p>An enzyme-protein complex that removes introns.</p> Signup and view all the answers

What is the anticodon of tRNA that pairs with the given codon?

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

The third nucleotide in the mRNA codons always determines the specific tRNA required for amino acid delivery.

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

What is the process by which a tRNA molecule binds to its corresponding amino acid called?

<p>Aminoacylation</p> Signup and view all the answers

Translation begins when the large and small ribosomal subunits interact with an mRNA molecule and the first _______ binds to the AUG start codon.

<p>aminoacyl-tRNA</p> Signup and view all the answers

Which specialized tRNA is used during the initiation of translation?

<p>tRNA for methionine (B)</p> Signup and view all the answers

Match the ribosomal sites with their functions:

<p>A site = Binds incoming aminoacyl-tRNA P site = Holds the growing polypeptide chain E site = Exit site for tRNA after delivering the amino acid</p> Signup and view all the answers

How many different amino acids are delivered by tRNA according to the wobble hypothesis?

<p>20 (C)</p> Signup and view all the answers

What occurs during the scanning process in translation initiation?

<p>The initiator complex moves along the mRNA until it reaches the AUG start codon.</p> Signup and view all the answers

Flashcards

Transcription

The process of converting genetic information from DNA to RNA.

RNA Polymerase

The enzyme responsible for creating RNA from a DNA template.

Promoter

A specific sequence of DNA that signals the start of a gene. It allows RNA polymerase to bind and begin transcription.

TATA Box

A specific promoter sequence in eukaryotes, rich in adenine and thymine (A-T) base pairs.

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Coding Strand

The DNA strand that is not used as a template for RNA synthesis but has the same sequence as the newly synthesized RNA molecule.

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Template Strand

The DNA strand that is used as a template for RNA synthesis.

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Elongation

The process of adding nucleotides to an RNA molecule one by one, using the DNA template strand as a guide.

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RNA-DNA Hybrid

A short region of hybrid RNA-DNA duplex that forms temporarily during RNA synthesis.

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Gene Expression

The process by which cells use the genetic information in DNA to create proteins.

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Central Dogma

The central dogma is the flow of genetic information from DNA to RNA to protein.

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Why can't protein be synthesized directly from DNA?

DNA is double-stranded and located in the nucleus, while RNA is single-stranded and can leave the nucleus to go to the ribosomes.

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Translation

The process of using the information in mRNA to build a protein. It involves translating the mRNA sequence into an amino acid sequence.

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DNA Replication

The process of making an exact copy of a DNA molecule.

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Leading Strand

The strand of DNA that is synthesized continuously during DNA replication.

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Transcription - Elongation

The process of creating many copies of mRNA from a single gene, allowing for efficient protein production.

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Termination Sequence

A sequence of bases at the end of a gene that signals the RNA polymerase to stop transcribing.

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Messenger RNA (mRNA)

The RNA version of a gene encoded by DNA, which serves as the intermediary between DNA and ribosomes for protein synthesis.

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Transfer RNA (tRNA)

A short RNA molecule that carries amino acids to ribosomes during protein synthesis.

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Ribosomal RNA (rRNA)

A type of RNA that combines with proteins to form ribosomes, the sites of protein synthesis.

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Post-Transcriptional Processing

The modifications that occur to newly synthesized pre-mRNA before it can leave the nucleus and be translated into protein.

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Why is producing many copies of mRNA necessary?

The process of creating many copies of mRNA from a single gene.

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Aminoacylation

The process of attaching an amino acid to its corresponding tRNA molecule.

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Aminoacyl-tRNA

A tRNA molecule carrying its specific amino acid.

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Anticodon

The three-base sequence on the tRNA that recognizes and binds to a complementary codon on the mRNA.

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Codon

The three-base sequence on the mRNA that determines which amino acid will be added to the growing polypeptide chain.

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P site

The site on the ribosome where the initiating methionine tRNA binds.

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A site

The site on the ribosome where the next incoming aminoacyl-tRNA binds.

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Wobble Hypothesis

The hypothesis that the third nucleotide in the codon can wobble or have some flexibility in its pairing with the anticodon, allowing for fewer tRNA molecules to be needed for all the codons.

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3' Poly(A) Tail

A chain of adenine nucleotides added to the 3' end of pre-mRNA, protecting it from degradation in the cytosol.

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5' Cap (5' G-cap)

A sequence of seven guanines added to the 5' end of pre-mRNA, serving as a recognition site for ribosomes to initiate translation.

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Exon

A coding sequence within a gene that is retained in the mature mRNA after splicing and contributes to the final protein product.

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Intron

A non-coding sequence within a gene that is removed from the pre-mRNA during splicing and does not contribute to the final protein product.

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Small Ribonucleoprotein (snRNP)

A protein complex that binds to introns and marks them for removal during RNA splicing.

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Spliceosome

A complex of proteins and RNA molecules that removes introns from pre-mRNA during splicing.

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Alternative Splicing

A process where different combinations of exons are joined together to produce multiple mature mRNA transcripts from a single gene, leading to the production of different proteins.

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What is a mutation?

A permanent change in the nucleotide sequence of a cell's DNA. It occurs when there is an error in DNA replication or repair.

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What are chromosomal mutations?

Mutations that affect multiple genes, often involving large sections of DNA. These can include deletions, duplications, inversions, and translocations.

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What are single-gene mutations?

Mutations that affect a single gene, usually involving a change in a single base pair. These can result in a loss or gain of function.

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What are mutagens?

Events or substances that increase the rate of DNA changes in an organism's genome. These can include radiation, certain chemicals, and viruses.

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What happens during polypeptide chain elongation?

The process of adding amino acids to a growing polypeptide chain during protein synthesis. It involves multiple steps, including the binding of tRNA with the correct amino acid to the A-site of the ribosome, peptide bond formation, and translocation of the ribosome.

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What is protein synthesis?

The process of decoding the genetic information in mRNA to build a protein. It involves initiation, elongation, and termination phases.

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What is a codon?

A specific sequence of three nucleotides in mRNA that codes for a particular amino acid.

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How does a ribosome move along an mRNA?

The process by which a ribosome moves along the mRNA molecule, reading codons and adding corresponding amino acids to the growing polypeptide chain.

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Study Notes

DNA Replication Review

  • Given a DNA sequence 5'-CCTAGAA-3', the complementary strand is 3'-GGATCTT-5'.
  • Given a DNA sequence 5'-CGCATGTAGCGA-3', the complementary strand is 3'-GCGTACATCGC-5'.
  • Given a DNA sequence 5'-CGCATGTAGCGA-3', the lagging strand would have the sequence 5'-TCG-3'.

Transcription

  • DNA is converted to RNA to synthesize proteins
  • DNA cannot be directly translated to proteins
  • Transcription is the process where DNA information is copied into RNA

Transcription Differences: Eukaryotes vs. Prokaryotes

  • Eukaryotes: Transcription occurs in the nucleus. Multiple RNA polymerases are involved. Pre-mRNA is transcribed, then processed. Introns are removed, and exons are joined together.
  • Prokaryotes: Transcription occurs in the cytoplasm. One RNA polymerase transcribes all genes. mRNA is translated directly. No introns to remove.

Transcription - Initiation

  • RNA polymerase binds to the DNA, unwinding it.
  • The enzyme binds to a promoter sequence.
  • Promoters are sequences on the DNA strand that allow RNA polymerase to attach (this sequence varies slightly).
  • Eukaryotes contain TATA boxes, Prokaryotes contain TATAAT sequences.

Transcription - Elongation

  • RNA polymerase does not need a primer.
  • RNA is produced in the 5' to 3' direction
  • The template strand is read 3' to 5'.
  • As RNA polymerase moves, DNA unwinds.
  • Multiple RNA polymerase molecules can bind.

Transcription - Termination

  • Transcription ends when RNA polymerase recognizes a termination sequence.
  • A termination sequence is a specific set of bases that signals to RNA polymerase to stop and release the new RNA strand.

Different Types of RNA

  • mRNA: Carries genetic information from DNA to ribosomes. Varies in length, depending on the length of the gene.
  • tRNA: Delivers amino acids to ribosomes. Transports specific amino acids. Short; 70 to 90 nucleotides per unit.
  • rRNA: Forms ribosomes, where protein synthesis occurs. Binds with proteins to form ribosomes; length varies.

Post-Transcriptional Modifications

  • Newly synthesized pre-mRNA is not ready to leave the nucleus.
  • Modifications include:
    • 5' cap (7G's): Protects mRNA.
    • 3' poly(A) tail: Prevents degradation.
  • Removes introns, joins exons.

Spliceosome

  • Splicesosome is an enzyme complex removing introns in pre-mRNA.
  • Several snRNPs aid the spliceosome.

Alternative Splicing

  • Exons can be joined together in different combinations in RNA, creating multiple possible polypeptides.
  • Alternative splicing allows for multiple proteins to develop from a single gene.
  • This is a method for creating multiple possible polypeptides from a single gene.

DNA Mutations

  • A mutation is a permanent change in the DNA nucleotide sequence.
  • Chromosomal mutations: Large-scale changes affect multiple genes (deletions, duplications, inversions, translocations).
  • Single-gene mutations: Point mutations affect single genes, affecting function (substitutions, insertions, deletions of single base pairs).
  • Mutagens: Increase the rate of DNA changes (transposons, chemicals, radiations).

Codon Chart

  • A codon is three consecutive nucleotides coding for an amino acid.
  • The codon chart translates codons into amino acids.

Translation

  • The process of transferring genetic information into an amino acid sequence
  • Translation is the biological process of producing proteins according to the instructions made in mRNA.

Translation Steps: Initiation, Elongation, and Termination

  • Initiation: Ribosomes interact with mRNA and the first tRNA.
  • Elongation: tRNA bring amino acids to the ribosome, forming a polypeptide chain.
  • Termination: Recognition of a stop codon signals release of the polypeptide chain and ribosome disassembles.

Ribosome Structure

  • Ribosomes are large complex structures composed of rRNA and ribosomal proteins.
  • Ribosomes have binding sites for mRNA and tRNA molecules.

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DNA Expression 12th Grade PDF

Description

Test your knowledge on the process of protein synthesis, including the roles of enzymes, mutations, and transcription. This quiz covers key concepts such as codons, peptide bonds, and various mutations in DNA. Perfect for students looking to reinforce their understanding of molecular biology.

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