Gene Expression and Protein Structure
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Questions and Answers

What is the main purpose of mRNA processing?

  • To replicate DNA
  • To facilitate the breakdown of mRNA
  • To modify mRNA for translation (correct)
  • To remove exons from the RNA sequence

Which nitrogenous base is found in RNA but not in DNA?

  • Adenine (A)
  • Uracil (U) (correct)
  • Cytosine (C)
  • Thymine (T)

During transcription, what role does RNA polymerase play?

  • It transports mRNA to the ribosome
  • It unwinds the DNA segment (correct)
  • It synthesizes proteins directly
  • It bonds amino acids together

What happens to the RNA molecule after it is synthesized?

<p>It is processed and modified (B)</p> Signup and view all the answers

How does the structure of DNA differ from that of RNA?

<p>DNA is double-stranded, RNA is single-stranded (A)</p> Signup and view all the answers

What is the significance of the Guanine Cap and Poly A tail in mRNA?

<p>They prevent degradation of mRNA (C)</p> Signup and view all the answers

Which of the following is true about introns?

<p>They are removed during mRNA splicing (C)</p> Signup and view all the answers

Where does mRNA processing occur in eukaryotic cells?

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

What function does the 5' cap serve in the primary mRNA transcript?

<p>It stabilizes the mRNA and aids in ribosome binding. (A)</p> Signup and view all the answers

Which regions of DNA are transcribed but not translated?

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

Which of the following is true about mature mRNA?

<p>It includes exons, a guanine cap, and a poly A tail. (D)</p> Signup and view all the answers

What is the role of codons in the process of translation?

<p>They determine the sequence of amino acids in a protein. (D)</p> Signup and view all the answers

Which process is responsible for removing introns from the pre-mRNA?

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

What is the significance of the universal nature of the DNA code?

<p>It allows any organism to use the same 20 amino acids. (B)</p> Signup and view all the answers

Where does the process of translation take place within the cell?

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

Which component is NOT included in the primary mRNA transcript?

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

What is the primary function of tRNA in the process of translation?

<p>To bind and transport amino acids to the ribosome (D)</p> Signup and view all the answers

What feature of tRNA allows it to bind to the corresponding mRNA codon?

<p>The anticodon region (B)</p> Signup and view all the answers

Which nucleotide sequence represents the anticodon for the mRNA codon UGG?

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

Which of the following statements about the start codon is true?

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

During translation, what happens to the tRNA molecule once it has delivered its amino acid?

<p>It is recycled back to the cytoplasm. (B)</p> Signup and view all the answers

What is the initial step in the process of translation initiation?

<p>The small ribosomal subunit assembles at the start codon. (D)</p> Signup and view all the answers

How does the ribosome move along the mRNA during translation?

<p>One codon at a time (C)</p> Signup and view all the answers

What is the role of the ribosomal RNA (rRNA) in the translation process?

<p>It binds with mRNA and stabilizes the ribosome structure. (B)</p> Signup and view all the answers

What symptom would likely arise from a deficiency in lactase?

<p>Inability to digest lactose found in milk (B)</p> Signup and view all the answers

Which component of a nucleotide differs between DNA and RNA?

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

What is the primary function of hemoglobin in red blood cells?

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

What characterizes the structure of DNA?

<p>Double-stranded and antiparallel (A)</p> Signup and view all the answers

What condition results from a deficiency in clotting proteins?

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

Which of the following nitrogenous bases is present only in RNA?

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

What is the role of acetaldehyde dehydrogenase in the body?

<p>Breaking down acetaldehyde from alcohol (C)</p> Signup and view all the answers

How are nucleotides linked within a single strand of DNA?

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

What is the primary cause of sickle-cell anemia?

<p>A mutation in the gene for hemoglobin (D)</p> Signup and view all the answers

Which point mutation is most likely to result in a nonfunctional protein?

<p>Both nucleotide deletion and insertion (D)</p> Signup and view all the answers

How do repair enzymes contribute to genetic stability?

<p>They correct errors during DNA replication (C)</p> Signup and view all the answers

Which of the following statements about mutations is correct?

<p>Most mutations do not significantly affect survival (B)</p> Signup and view all the answers

What accurately describes a nucleotide deletion?

<p>It can cause a frameshift mutation. (C)</p> Signup and view all the answers

Which environmental factor is classified as a mutagen?

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

Which type of mutation is least likely to change the amino acid sequence?

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

What is a common outcome of a frameshift mutation?

<p>The alteration of multiple amino acids (D)</p> Signup and view all the answers

What forms the sides of the DNA ladder structure?

<p>Phosphate and sugar molecules (C)</p> Signup and view all the answers

What is the significance of complementary base pairing in DNA?

<p>It ensures that T binds with A and C binds with G (C)</p> Signup and view all the answers

During DNA replication, which enzyme is responsible for adding new nucleotides?

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

Which of the following describes the structure of the DNA double helix?

<p>A coiled structure resembling a twisted ladder (C)</p> Signup and view all the answers

What are histones in relation to DNA?

<p>Proteins that help package DNA into chromatin (B)</p> Signup and view all the answers

What is the result of DNA replication?

<p>Two identical DNA molecules, each with one old and one new strand (D)</p> Signup and view all the answers

Why is DNA replication described as occurring in many places simultaneously?

<p>To speed up the replication process (B)</p> Signup and view all the answers

What is the approximate number of chromosomes in a human body cell?

<p>46 (B)</p> Signup and view all the answers

Flashcards

mRNA processing

Modifying mRNA to form the final transcript, involving removal of introns and adding a 5' cap and poly-A tail.

Protein folding

Process where a polypeptide chain folds into a specific 3D shape, determining its function and ultimately creating traits.

Transcription

Process that copies a DNA gene into a mRNA molecule, using RNA polymerase.

RNA polymerase

Enzyme that unwinds DNA, matches RNA nucleotides, and builds the mRNA molecule during transcription.

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Introns

Non-coding segments of mRNA that are removed during mRNA processing (splicing).

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mRNA splicing

The process of removing introns from newly created mRNA molecules.

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Guanine cap

A modified guanine nucleotide added to the 5' end of mRNA, protecting it and assisting ribosome binding.

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Poly-A tail

A series of adenine nucleotides added to the 3' end of mRNA, protecting it and aiding in its journey to the ribosome.

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5' Capping

Adding a specific guanine nucleotide to the 5' end of a primary transcript.

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Splicing

Removing introns and joining exons together to create mature mRNA.

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Primary mRNA Transcript

The initial mRNA molecule containing both exons and introns.

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Mature mRNA Transcript

The processed mRNA molecule containing only exons, a 5' cap, and a PolyA tail.

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Codon

A sequence of three nucleotides in mRNA that corresponds to an amino acid.

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Translation

The process of converting mRNA's nucleotide sequence into a polypeptide chain.

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Ribosome

The cellular organelle where translation occurs.

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DNA double helix

A twisted ladder-like structure of DNA, where the sides are made of phosphate and sugar, and the rungs are made of bases.

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Complementary base pairing

A rule where T only bonds with A, and C only bonds with G in DNA.

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Human chromosome number

The typical human body cell contains 46 chromosomes (23 pairs).

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DNA Replication

The process of creating an identical copy of a DNA molecule.

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DNA Helicase

An enzyme that unwinds and unzips the DNA double helix during replication.

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Chromatin

DNA wound around histone proteins, compacting it within the cell nucleus.

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Histones

Proteins that DNA wraps around to organize it within the nucleus.

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tRNA

A single-stranded RNA molecule that folds into a cloverleaf shape and carries a specific amino acid to the ribosome during translation. It has an anticodon that pairs with the mRNA codon.

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Anticodon

A three-nucleotide sequence on tRNA that is complementary to a codon on mRNA. It ensures the correct amino acid is added to the growing polypeptide chain.

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Start Codon

The first codon in an mRNA molecule, typically AUG, that signals the beginning of translation and specifies the amino acid methionine.

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Ribosome Binding Region (RBR)

A specific sequence on mRNA that binds to the small ribosomal subunit, initiating translation.

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P Site

The site on the ribosome that holds the tRNA carrying the growing polypeptide chain.

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A Site

The site on the ribosome where the next tRNA carrying an amino acid binds.

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Stop Codon

A three-nucleotide sequence in mRNA (UAA, UAG, or UGA) that signals the end of translation and releases the newly synthesized polypeptide.

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Mutation

A permanent change in the DNA sequence. This alteration can be small, like a single base change, or larger, such as a deletion or insertion.

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Point Mutation

A change in a single base pair within a gene. It can affect the protein coded by the gene, having varying consequences.

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Frameshift Mutation

A mutation that shifts the reading frame of a gene, leading to a completely different protein.

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Nucleotide Substitution

Changing one base for another within a gene. This might have no effect, or it could alter the amino acid encoded.

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Nucleotide Deletion

Removing a base from the DNA sequence, changing the reading frame and potentially leading to a nonfunctional protein.

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Why are DNA repair mechanisms important?

Repair enzymes constantly scan DNA for errors and try to correct them. This prevents the accumulation of harmful mutations.

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Nucleotide Insertion

Adding an extra base to the DNA sequence, shifting the reading frame and likely disrupting normal protein function.

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Why are most mutations harmful?

Mutations can disrupt the normal function of genes, leading to diseases. Most mutations are harmful because they reduce our ability to survive in our environment.

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What are the monomers of nucleic acids?

Nucleotides are the building blocks of nucleic acids, like DNA and RNA. Each nucleotide consists of three parts: a sugar, a nitrogenous base, and a phosphate group.

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What are the two types of nucleic acids?

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the two main types of nucleic acids. They differ in their sugar, nitrogenous bases, and structure.

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What is the difference between ribose and deoxyribose?

Ribose is the sugar found in RNA, while deoxyribose is the sugar found in DNA. Deoxyribose has one less oxygen atom than ribose.

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What are the four nitrogenous bases in DNA?

Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) are the four nitrogenous bases found in DNA. They form pairs: A with T and G with C.

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What are the four nitrogenous bases in RNA?

Adenine (A), Guanine (G), Cytosine (C), and Uracil (U) are the four nitrogenous bases found in RNA. They form pairs: A with U and G with C.

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What does 'antiparallel' mean in DNA structure?

In DNA, the two strands of nucleotides run in opposite directions. One strand goes from 5' to 3', while the other goes from 3' to 5'. This is called antiparallel.

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What holds the two DNA strands together?

Hydrogen bonds between the nitrogenous bases hold the two strands of DNA together. These bonds are weak but numerous, making DNA stable.

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What is the function of DNA?

DNA stores and transmits genetic information from one generation to the next. It acts as a blueprint for all the proteins in an organism.

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Study Notes

Gene Expression and Proteins

  • Proteins are formed from different arrangements of 20 amino acids, like words from letters.
  • Humans can make some amino acids but need others (essential amino acids) from food.
  • Proteins differ based on the number of amino acids (length), order of amino acids, and type of amino acids.
  • Amino acids are grouped by chemical properties, like hydrophobic (nonpolar), polar, and charged.
  • Hydrophobic amino acids tend to be nonpolar; they frequently interact with each other.
  • Polar amino acids have groups that attract water; they often participate in hydrogen bonding and other interactions.
  • Charged amino acids have charged groups that interact with other charged groups.
  • Cysteine amino acids are capable of forming disulfide bridges with other cysteine amino acids.

Protein Structure

  • Primary structure: Linear sequence of amino acids, held together by peptide bonds.
  • Secondary structure: Local folds (alpha helices, beta sheets) formed by hydrogen bonds.
  • Tertiary structure: 3-D shape resulting from R-group interactions, including hydrophobic interactions, hydrogen bonds, ionic bonding, and disulfide bonds (ex. final or functional protein)
  • Quaternary structure: Multiple polypeptide chains combining to form a functional protein.

Sickle Cell Anemia

  • A disease caused by a mutation in the hemoglobin protein. One change in an amino acid sequence causes a change in hemoglobin structure.
  • In hemoglobin, the order leads to red blood cells having a sickle shape, preventing efficient oxygen transport.

Protein Denaturation

  • Loss of secondary, tertiary, or quaternary structure due to factors like high temperatures, extreme pH, and high salt concentrations.
  • These factors disrupt stabilizing interactions (e.g., hydrogen bonds, ionic bonds, and disulfide bridges).

Proteins Determine Traits

  • All cells have genetic material in the form of DNA.
  • Genes code for proteins that determine traits.
  • Genes directly influence organism characteristics.

Nucleic Acids

  • Two main types of nucleic acids: DNA and RNA.
  • Nucleotides are the building blocks of nucleic acids.
  • Each nucleotide has a sugar (ribose or deoxyribose), a nitrogenous base (A, T, C, G, or U), and a phosphate group.
  • DNA is double-stranded in a double helix shape, and RNA is single-stranded with a different sugar and bases
  • DNA and RNA have different sugars. DNA has deoxyribose, and RNA has ribose.
  • DNA has thymine, and RNA has uracil.
  • DNA is typically larger than RNA in a cell.
  • DNA strands run antiparallel, meaning they are oriented in opposite directions.

DNA Replication

  • The process of copying DNA prior to cell division to ensure each new cell gets a complete copy of the genetic material.
  • DNA replication is semi-conservative, one strand from the parent DNA and a newly synthesized strand.

Gene Expression Protein Building: Transcription and Translation

  • Transcription: DNA code copied into mRNA.
  • Translation: mRNA code used to assemble amino acids into a protein.
  • mRNA: Messenger RNA
  • tRNA: Transfer RNA
  • rRNA: Ribosomal RNA
  • Ribosomes are the site of protein synthesis.

Mutations

  • Changes in DNA sequence.
  • Most, but not all mutations are harmful.
  • Mutations can lead to altered proteins that may have impaired function.
  • Some mutations can be beneficial or neutral.
  • Mutations can be caused by errors in DNA replication, exposure to environmental mutagens.
  • Deletions and additions can shift the reading frame, meaning the sequence of amino acids is altered from the point of the mutation forward. Substitution of a nucleotide can lead to different amino acids (e.g. sickle cell).

Point Mutations

  • Changes in a single nucleotide.
  • Substitution: Replace one nucleotide with another.
  • Deletion: Removing a nucleotide.
  • Insertion: Adding a nucleotide.
  • Frameshift mutations (insertion or deletion) result in changes in the reading frame, affecting the entire amino acid sequence downstream from the mutation.

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Honors Biology 2A: Gene Expression - McCarthy 24-25 PDF

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Explore the fascinating world of protein formation and structure in this quiz. Learn about the various amino acids, their properties, and how they combine to create functional proteins. Discover the significance of primary and secondary protein structures in biological systems.

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