Biology Chapter: RNA and Protein Synthesis

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Questions and Answers

Which RNA type is primarily involved in carrying amino acids during protein synthesis?

  • messenger RNA (mRNA)
  • ribosomal RNA (rRNA)
  • small nuclear RNA (snRNA)
  • transfer RNA (tRNA) (correct)

Transcription occurs in the nucleus of eukaryotic cells.

True (A)

What indicates the termination of protein synthesis?

A stop codon

In eukaryotes, mRNA is processed and transported to the __________.

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

Match the following processes with their descriptions:

<p>Transcription = DNA to mRNA synthesis Translation = mRNA to protein synthesis Termination = Process of ending protein synthesis Mutation = Change in genetic information</p> Signup and view all the answers

Which of these factors can cause mutations?

<p>All of the above (D)</p> Signup and view all the answers

A point mutation is a change involving multiple nucleotides.

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

What are the main steps involved in gene expression?

<p>Transcription and translation</p> Signup and view all the answers

What occurs during DNA replication?

<p>Two identical double helices are formed. (D)</p> Signup and view all the answers

A DNA strand consists of only phosphate groups and nitrogen bases.

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

What sequences are complementary in DNA base pairing?

<p>A-T, G-C</p> Signup and view all the answers

What is the first step of translation?

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

Transcription of RNA occurs in the ______ of the cell.

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

The process of elongation in translation does not require energy.

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

Match the process with its description:

<p>Transcription = Formation of mRNA from DNA Translation = Synthesis of proteins from mRNA PCR = Amplification of DNA segments DNA Replication = Copying of DNA into identical strands</p> Signup and view all the answers

What is the role of tRNAs during translation?

<p>tRNAs bring amino acids to ribosomes according to the codon sequence in mRNA.</p> Signup and view all the answers

What is the role of tRNA during translation?

<p>To carry amino acids to the mRNA (A)</p> Signup and view all the answers

The start codon in mRNA is ____.

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

During transcription, the DNA helix unwinds and unzips.

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

List one effect of a mutation on protein function.

<p>It can cause a change in amino acid sequence that produces a protein that does not function properly.</p> Signup and view all the answers

Match the step of translation with its description:

<p>Initiation = Assembly of ribosomal subunits with mRNA and tRNA Elongation = Addition of amino acids to the growing polypeptide chain Termination = Release of the newly formed protein from the ribosome Polyribosome = Multiple ribosomes translating one mRNA simultaneously</p> Signup and view all the answers

Which component is necessary for peptide bond formation during elongation?

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

During termination, energy is required to disassemble the components of translation.

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

Name the enzyme that breaks hydrogen bonds between DNA strands during replication.

<p>DNA helicase</p> Signup and view all the answers

What is the primary function of DNA ligase in recombinant DNA technology?

<p>To seal the gene and vector DNAs (D)</p> Signup and view all the answers

Cancer cells are genetically stable and do not have mutations.

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

What is the purpose of gene cloning?

<p>To study gene functions, produce proteins, create transgenic organisms, and cure diseases.</p> Signup and view all the answers

During DNA replication, __________ are formed because DNA Polymerase can only add nucleotides to the 3' end of a strand.

<p>Okazaki fragments</p> Signup and view all the answers

Match the following enzymes with their functions in DNA replication:

<p>DNA helicase = Unzips the double helix DNA polymerase = Adds new nucleotides to the strand DNA ligase = Seals gaps between Okazaki fragments</p> Signup and view all the answers

Which of the following is a product of recombinant DNA technology?

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

What change occurs in cancer cells that enables them to metastasize?

<p>They can survive and proliferate in new tissues.</p> Signup and view all the answers

The mRNA codon A-U-C codes for the amino acid isoleucine.

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

What is the complementary base sequence of the DNA codon T-A-G?

<p>A-T-C (B)</p> Signup and view all the answers

The tRNA anticodon UUU signals to the ribosome to bring glutamine.

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

What is the amino acid associated with the tRNA anticodon GAG?

<p>Glutamic acid</p> Signup and view all the answers

The bonds that hold amino acids together in a protein are called _______.

<p>peptide bonds</p> Signup and view all the answers

Match the following DNA sequences with their corresponding mRNA codons:

<p>TAG = AUC AAA = UUU GTC = CAG AAG = UUC</p> Signup and view all the answers

What would happen if the last three bases in the DNA sequence TACTTCAAACCG were changed to ATC?

<p>The protein would be incomplete and non-functional. (B)</p> Signup and view all the answers

There are three hydrogen bonds between adenine and thymine in DNA.

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

How many nucleotides on the mRNA sequence code for a polypeptide chain with 10 amino acids?

<p>30</p> Signup and view all the answers

How many peptide bonds are required for a protein that is 9 amino acids long?

<p>8 (B)</p> Signup and view all the answers

DNA replication is a process that is entirely conservative.

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

What enzyme is responsible for unzipping the DNA during replication?

<p>DNA helicase</p> Signup and view all the answers

The ______ carries the genetic code from DNA to the ribosomes for protein synthesis.

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

Match the DNA replication enzymes with their functions:

<p>DNA helicase = Unzips the DNA double helix DNA polymerase = Adds nucleotides to the growing DNA strand DNA ligase = Joins Okasaki fragments</p> Signup and view all the answers

What is a key feature of the genetic code?

<p>It is universal across all living organisms. (C)</p> Signup and view all the answers

Mutations in DNA can only lead to genetic disorders through environmental mutagens.

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

Name a genetic disorder that can result from mutations in DNA.

<p>Sickle cell anemia</p> Signup and view all the answers

Flashcards

Transcription

Process of converting genetic information from DNA into RNA.

Translation

Process of translating RNA sequence into a protein.

Ribosome

The site where proteins are synthesized.

tRNA

A small RNA molecule that carries a specific amino acid to the ribosome during translation.

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Initiation

Process of assembling components for protein synthesis.

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Elongation

Process of adding amino acids to the growing polypeptide chain.

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Termination

Process of ending protein synthesis.

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DNA helicase

An enzyme that unwinds and separates DNA strands.

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Gene Expression

The process of making a protein from a DNA template. It includes two main steps: transcription and translation.

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Messenger RNA (mRNA)

A type of RNA that carries the genetic code from DNA to ribosomes, where it is translated into proteins.

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Transfer RNA (tRNA)

A type of RNA that carries specific amino acids to the ribosomes during protein synthesis. It recognizes the codons on the mRNA and brings the corresponding amino acid.

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Ribosomal RNA (rRNA)

A type of RNA that is a structural component of ribosomes. It helps in the formation of peptide bonds between amino acids.

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Mutation

A change in the DNA sequence. Errors in replication, mutagens, and transposons can cause mutations.

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Point mutation

A single nucleotide change in the DNA sequence. Can have various effects on protein activity.

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Silent mutation

A change in the DNA sequence that does not alter the amino acid sequence of the resulting protein.

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Missense mutation

A change in the DNA sequence that results in a different amino acid being incorporated into the protein, potentially affecting its function.

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Nonsense mutation

A change in the DNA sequence that introduces a stop codon, prematurely terminating protein synthesis.

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Nucleotides

The building blocks of DNA, consisting of a phosphate group, a deoxyribose sugar, and a nitrogen-containing base.

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DNA replication

The process of copying a DNA molecule to produce two identical DNA molecules.

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RNA polymerase

The enzyme responsible for catalyzing the synthesis of RNA from a DNA template during transcription.

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Polymerase chain reaction (PCR)

A technique used to amplify a specific DNA sequence by repeated cycles of DNA replication.

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Recombinant DNA

DNA molecule containing a gene from another organism inserted into its own genes.

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Plasmid

A circular DNA molecule found in bacteria, used as a vector for gene cloning.

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DNA ligase

An enzyme that joins DNA fragments together, essential in DNA replication and gene cloning.

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Gene cloning

The process of introducing a gene into a vector (like a plasmid) to create recombinant DNA, allowing for gene multiplication.

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Restriction sites

Regions of DNA recognized by restriction enzymes, often producing 'sticky ends' that can base-pair with complementary sequences.

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Okazaki fragments

Sections of DNA synthesized discontinuously on the lagging strand during DNA replication.

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Complementary DNA sequence

The sequence of bases on a DNA strand that matches the mRNA codon.

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tRNA anticodon

The three-base sequence on a tRNA molecule that recognizes and binds to a specific mRNA codon during translation.

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Peptide bonds

The bonds that hold amino acids together in a polypeptide chain.

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Hydrogen bonds

The bonds that hold the two strands of DNA together.

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Study Notes

Gene Expression Overview

  • During transcription, DNA's base sequence is copied into mRNA.
  • During translation, tRNAs bring amino acids, ordered by mRNA codons, to ribosomes.
  • Ribosomes move along mRNA, linking amino acids to form proteins.
  • Multiple ribosomes can translate an mRNA simultaneously (polyribosome).

Translation Steps

  • Initiation: Ribosome assembly with mRNA, initiator tRNA (methionine), and start codon (AUG)
  • Elongation: Repeated steps of tRNA-amino acid binding at the A site, peptide bond formation, ribosome movement, and empty tRNA release from E site
  • Termination: Stop codon on mRNA, release factor binding, protein release, ribosome disassembly

DNA Replication

  • DNA polymerase catalyzes new nucleotide addition via complementary base pairing.
  • Replication is different for each strand (leading vs. lagging).
  • Leading strand synthesis follows helicase; lagging strand synthesizes in Okazaki fragments.
    • DNA ligase connects Okazaki fragments and seals breaks.
  • DNA helicase separates DNA strands by breaking H-bonds.

mRNA Processing (Eukaryotes)

  • Primary mRNA is processed before leaving the nucleus.
  • Introns (non-coding regions) are removed.
  • Exons (coding regions) are joined.
  • A cap and poly-A tail are added.

Transfer RNA (tRNA)

  • tRNA molecules bring amino acids to ribosomes.
  • tRNA has a specific anticodon complementary to an mRNA codon.
  • One end attaches to the amino acid.

Nonfunctional Proteins

  • Frameshift mutations (insertions/deletions) cause changes to codons, making the protein nonfunctional, e.g. THE CAT ATE THE RAT -> THE ATA TET HER AT
  • Mutations in pathways can affect the entire cellular process.

Mutations and Cancer

  • Cancer development involves accumulating mutations.
  • Cancer starts as benign growths of abnormal cells.
  • Mutations can cause cells to invade lymphatic and blood vessels, leading to metastases.

Gene Cloning

  • Restriction enzymes cleave DNA for gene isolation and insertion into vectors, often plasmids.
  • DNA ligase seals the gene and vector DNA.
  • Host cell takes up the recombinant plasmid, initiating gene cloning.

Polymerase Chain Reaction (PCR)

  • PCR creates many copies of a DNA segment in a test tube.
  • Steps: denaturation, annealing, extension.
  • Each cycle doubles the DNA amount.
  • PCR is used for DNA analysis and individual identification (e.g., STR profiling).

Genetic Code

  • Code is universal and degenerate (multiple codons for one amino acid).
  • mRNA codons are triplets.
  • Codons specify amino acids.

Causes of Mutations

  • Replication errors are rare (1 mistake per billion nucleotide pairs).
  • Mutagens (radiation, chemicals) cause mutations.
  • Transposons move within/between chromosomes; altering gene expression.

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