Nucleic Acids and DNA Replication
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Questions and Answers

What is the primary function of DNA in an organism?

  • To act as an energy source
  • To transport oxygen
  • To store genetic information (correct)
  • To produce hormones

Which nitrogenous base pairs with adenine in DNA?

  • Guanine
  • Thymine (correct)
  • Uracil
  • Cytosine

What is the shape of a DNA molecule?

  • Linear strand
  • Triple helix
  • Single strand
  • Double helix (correct)

Which of the following correctly identifies the components of a nucleotide?

<p>A phosphate group, a pentose sugar, and a nitrogenous base (A)</p> Signup and view all the answers

What type of sugar is found in RNA?

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

Which of the following statements about purines and pyrimidines is true?

<p>Purines consist of adenine and guanine (A)</p> Signup and view all the answers

What was Erwin Chargaff's significant discovery regarding DNA?

<p>The amount of guanine equals the amount of cytosine (D)</p> Signup and view all the answers

Which statement describes the directionality of DNA strands?

<p>One strand runs 3' to 5' while the other runs 5' to 3' (D)</p> Signup and view all the answers

What was the main finding of the Hershey-Chase experiment?

<p>DNA is the genetic material of life. (A)</p> Signup and view all the answers

Which radioisotope was used to track DNA in the Hershey-Chase experiment?

<p>32P (A)</p> Signup and view all the answers

What role does helicase play in DNA replication?

<p>It breaks the hydrogen bonds between base pairs. (C)</p> Signup and view all the answers

What is meant by the term 'semi-conservative' in the context of DNA replication?

<p>Each new DNA molecule contains one original and one new strand. (D)</p> Signup and view all the answers

Which of the following enzymes is involved in adding nucleotides during DNA replication?

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

What happens to the viral DNA once it is injected into the host bacterial cell in the Hershey-Chase experiment?

<p>It is expressed and used to produce new viruses. (A)</p> Signup and view all the answers

Which component of the viruses used in the Hershey-Chase experiment remains outside the bacterial cell after infection?

<p>The protein capsid (B)</p> Signup and view all the answers

What is the primary purpose of single-stranded binding proteins during DNA replication?

<p>To prevent the two DNA strands from re-annealing. (A)</p> Signup and view all the answers

What is the first step in the initiation of translation?

<p>The small ribosomal subunit binds to the mRNA near the start codon. (B)</p> Signup and view all the answers

Which anticodon is carried by the first tRNA that binds during translation initiation?

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

During the elongation phase of translation, what happens after a tRNA molecule binds to the A site?

<p>A peptide bond is formed between the amino acids. (D)</p> Signup and view all the answers

What role does a release factor play during the termination of translation?

<p>It binds to the A site to facilitate polypeptide release. (B)</p> Signup and view all the answers

What is the nature of the reaction that forms peptide bonds during translation?

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

Which of the following best defines gene regulation?

<p>Any measure used to promote or suppress gene expression. (C)</p> Signup and view all the answers

What effect do acetyl groups have on gene expression when added to histones?

<p>They loosen DNA packing to promote gene expression. (B)</p> Signup and view all the answers

What is the outcome of methylation of genes?

<p>Tighter DNA packing to suppress gene expression. (D)</p> Signup and view all the answers

What is the primary role of the promoter region during transcription?

<p>It provides a binding site for transcription factors. (C)</p> Signup and view all the answers

What is the primary function of DNA polymerase III during DNA replication?

<p>It copies DNA in the 5' to 3' direction. (C)</p> Signup and view all the answers

What differentiates small proteins from large proteins?

<p>The number of amino acids in the chain. (C)</p> Signup and view all the answers

Which of the following statements about lagging strand synthesis is accurate?

<p>It consists of short segments called Okazaki fragments. (D)</p> Signup and view all the answers

Which of the following statements accurately describes RNA polymerase II?

<p>It synthesizes mRNA after transcription factors are in place. (C)</p> Signup and view all the answers

What role does DNA polymerase I play in DNA replication?

<p>It replaces RNA primers with DNA. (B)</p> Signup and view all the answers

What component is added to the 5' end of the immature mRNA during processing?

<p>A 5' cap of guanosine triphosphate (A)</p> Signup and view all the answers

Which of the following best describes the telomeres in regard to DNA replication?

<p>They shorten slightly with each DNA replication cycle. (D)</p> Signup and view all the answers

Which of the following accurately describes the transcription process?

<p>It results in the production of pre-mRNA. (B)</p> Signup and view all the answers

Which component is NOT part of the replisome during DNA replication?

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

What does the term 'introns' refer to in the context of gene structure?

<p>Noncoding DNA segments. (D)</p> Signup and view all the answers

What accurately describes the composition of chromatin?

<p>It includes both DNA and proteins, particularly histones. (B)</p> Signup and view all the answers

Which base is not used in RNA, forming a crucial distinction from DNA?

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

Which of the following molecules is considered noncoding DNA?

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

At which point does RNA polymerase II stop transcription?

<p>When it encounters the stop codon. (D)</p> Signup and view all the answers

What primary function does the H1 protein serve in the organization of DNA?

<p>It helps hold DNA to the nucleosome. (D)</p> Signup and view all the answers

What function does the poly-A tail serve for mRNA?

<p>It stabilizes mRNA, protects it from digestion, and aids in routing. (A)</p> Signup and view all the answers

Which statement is true regarding tRNA?

<p>tRNA is necessary for transporting amino acids to ribosomes during translation. (A)</p> Signup and view all the answers

Which of the following correctly describes the structure of ribosomes?

<p>Ribosomes have three binding sites for tRNA during translation. (C)</p> Signup and view all the answers

What is the total number of amino acids that can be coded for by the genetic code?

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

What differentiates prokaryotic ribosomes from eukaryotic ribosomes?

<p>The small and large subunits of prokaryotic ribosomes are different sizes than those of eukaryotes. (C)</p> Signup and view all the answers

Which of the following describes the codons in the genetic code?

<p>There are more codons than amino acids due to the redundancy of the genetic code. (A)</p> Signup and view all the answers

During protein synthesis, what happens when ribosomes translate mRNA?

<p>Ribosomes can synthesize proteins concurrently on the same mRNA strand. (D)</p> Signup and view all the answers

What role do spliceosomes play in RNA processing?

<p>They remove introns from pre-mRNA transcripts. (C)</p> Signup and view all the answers

Flashcards

Hershey-Chase Experiment

The experiment that proved DNA is the genetic material. It involved using bacteriophages to infect bacteria and labeling their protein and DNA with radioactive isotopes. By tracking the isotopes, they found that DNA, not protein, was injected into the bacteria, making DNA the genetic material.

Bacteriophages

Viruses that infect bacteria. They consist of a protein capsid surrounding their genetic material, which is injected into a host bacterial cell.

DNA Replication

The process of creating two identical DNA molecules from one original molecule. This is the foundation of cell division.

Origin of Replication

A single point on a DNA molecule where replication starts in prokaryotes.

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Helicase

The enzyme that unwinds and separates the two strands of DNA by breaking the hydrogen bonds between the bases.

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Single-stranded Binding Proteins

Proteins that bind to the separated DNA strands to prevent them from rejoining, giving time for DNA polymerase to work.

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DNA Polymerase III

Enzyme that adds nucleotides to the new DNA strand, following the base pairing rules (A with T, and C with G).

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RNA Primer

A short sequence of RNA nucleotides that acts as a primer, providing a starting point for DNA polymerase III to begin adding nucleotides.

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What is DNA?

DNA is a nucleic acid, a polymer made of repeating nucleotide units. Each nucleotide contains a pentose sugar, phosphate, and a nitrogenous base.

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What are the nitrogenous bases in DNA?

Adenine (A), guanine (G), cytosine (C), and thymine (T) are the four nitrogenous bases found in DNA.

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Describe the structure of DNA.

DNA has a double helix structure, where two strands are held together by hydrogen bonds between complementary base pairs. Adenine always pairs with thymine (A-T), and guanine always pairs with cytosine (G-C).

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What does it mean that DNA strands are antiparallel?

The two strands of DNA run in opposite directions, called antiparallel. This means one strand runs 5' to 3', while the other runs 3' to 5'.

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What is RNA?

RNA is a nucleic acid similar to DNA, except it uses uracil (U) instead of thymine (T) and has a ribose sugar instead of deoxyribose.

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What is Chargaff's rule?

Chargaff's rule states that in DNA, the amount of guanine (G) is equal to the amount of cytosine (C), and the amount of adenine (A) is equal to the amount of thymine (T).

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What are the parts of a nucleotide?

A nucleotide consists of three parts: a phosphate group, a pentose sugar, and a nitrogenous base. These parts are linked together in a specific order.

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Who discovered the structure of DNA?

Watson and Crick discovered the double helix structure of DNA, using data from Rosalind Franklin. Their work revolutionized our understanding of genetics.

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Primase

An enzyme that adds RNA primers to the parental DNA strand, allowing DNA polymerase III to bind and begin replication.

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Leading Strand

The DNA strand that is synthesized continuously in the same direction as the replication fork.

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Lagging Strand

The DNA strand that is synthesized discontinuously in the opposite direction of the replication fork, creating Okazaki fragments.

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DNA Ligase

An enzyme that joins the ends of DNA fragments together, creating a continuous DNA strand.

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Proofreading

The ability of DNA polymerase III to detect and correct errors during DNA replication.

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Genes

Coding segments of DNA responsible for producing proteins or various RNA molecules.

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Transcription

The process of copying a gene's DNA sequence into a messenger RNA (mRNA) molecule.

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Translation

The process of converting the genetic code in an mRNA molecule into a protein.

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Start Codon

The starting point of a gene on a chromosome that signals the beginning of transcription.

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Stop Codon

The ending point of a gene on a chromosome that signals the end of transcription.

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Promoter Region

A region of DNA located upstream from the start codon that initiates transcription.

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Transcription Factors

Proteins that bind to the promoter region and help RNA polymerase II initiate transcription.

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5' Cap

A molecule of guanosine triphosphate (GTP) added to the 5' end of immature mRNA during processing.

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Poly-A tail

A sequence of 50 to 250 adenine bases added to the 3' end of mRNA during RNA processing.

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Spliceosomes

Large molecular complexes that remove introns from pre-mRNA during RNA processing.

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tRNA

Folded RNA molecules that carry specific amino acids to the ribosome during protein synthesis.

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Ribosomes

Cellular organelles responsible for protein synthesis. Composed of rRNA and proteins.

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Genetic Code

The set of rules that relates codons in mRNA to specific amino acids.

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Anticodon

Three base pairs on tRNA that match a specific codon on mRNA during translation.

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Codon

A sequence of three nucleotides on mRNA that specifies a particular amino acid or a stop signal.

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Initiation (Translation)

The first step of translation where the small ribosomal subunit binds to the mRNA and scans for the start codon (AUG). Once found, the first tRNA with the anticodon UAC carrying methionine binds to the start codon, followed by the large ribosomal subunit binding to the small subunit, positioning the first tRNA in the P site.

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Elongation (Translation)

The process where the ribosome moves along the mRNA, reading codons and adding corresponding amino acids to the growing polypeptide chain. tRNA molecules with matching anticodons bring amino acids to the A site, forming peptide bonds with the previous amino acid in the P site. The ribosome then moves to the next codon, shifting the tRNA in the P site to the E site and the tRNA in the A site to the P site.

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Termination (Translation)

The final step of translation where the ribosome encounters a stop codon on the mRNA. A release factor binds to the A site, causing the polypeptide to detach from the ribosome.

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Condensation Reaction (Translation)

The process of forming a peptide bond between two amino acids, releasing a water molecule. This is a key reaction in protein synthesis.

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Gene Regulation

The regulation of gene expression, which can occur at various stages including before, during, or after transcription and translation. It can involve promoting or suppressing gene expression to control the final protein product.

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Enhancers (Pre-Transcriptional Regulation)

DNA segments that act as binding sites for activator proteins, which in turn interact with the promoter region and transcription factors to enhance transcription.

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Acetylation (Pre-Transcriptional Regulation)

Adding acetyl groups to histone proteins, which loosens DNA packing and promotes gene expression.

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Methylation (Pre-Transcriptional Regulation)

Adding methyl groups to histone proteins, which tightens DNA packing and inhibits gene expression.

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Study Notes

Nucleic Acids

  • DNA (deoxyribonucleic acid) contains genetic information for development and reproduction
  • RNA (ribonucleic acid) is also a nucleic acid
  • Nucleotides are the monomers of nucleic acids
  • Each nucleotide contains a pentose sugar, phosphate, and a nitrogenous base
  • DNA has deoxyribose sugar and bases A, G, C, and T
  • RNA has ribose sugar and bases A, G, C, and U
  • DNA forms a double helix
  • Bases in DNA pair up in complementary fashion: A with T, and C with G
  • Bonds between bases are hydrogen bonds
  • DNA strands run antiparallel (5' to 3' and 3' to 5')
  • RNA is typically single-stranded

DNA Replication

  • DNA replication is semi-conservative
  • Replication starts at a single origin, opening a replication bubble
  • Enzymes read the parent strand and construct a daughter strand
  • Replication continues bidirectionally
  • The process ensures each new DNA molecule has half of the original
  • Colored boxes represent enzymes, used in replication process.
  • Helicase breaks hydrogen bonds between bases
  • Single-stranded binding proteins prevent the strands from reconnecting
  • RNA primers are put in place by primase for DNA polymerase III attachment
  • DNA polymerase III copies DNA in 5' to 3' direction
  • Leading strand gets replicated continuously, lagging strand gets replicated in fragments (Okazaki fragments)
  • DNA polymerase I removes RNA primers and DNA ligase seals gaps
  • DNA Replication is a process where the DNA cell duplicates.

Gene Structure and Function

  • Genes are segments of DNA, with specific coding segments
  • Eukaryotic genes have exons (coding regions) and introns (non-coding regions)
  • Upstream from the start codon (in a gene) is the promoter region
  • Promoter region begins with TATA
  • Transcription factors bind to the promoter region

Gene Regulation

  • Gene regulation is the cell's controlled expression of genes.
  • Gene expression occurs before, during, and after transcription and translation
  • Enhancers enhance expression and promoter region is upstream of gene
  • Histones are proteins that DNA is associated with.
  • Acetylation of Histone proteins loosens the DNA structure, increasing expression.
  • Methylation of Histones proteins tightens the DNA structure, decreasing expression.

Transcription

  • Transcription is the first step in protein synthesis
  • RNA polymerase II binds to the promoter region
  • Breaks hydrogen bonds to transcribe the template strand of DNA to make mRNA.
  • mRNA molecules are made in the 5' to 3' direction
  • mRNA is called pre-mRNA initially and it needs processing before it can be translated

Translation

  • Ribosomes translate mRNA into proteins
  • tRNA brings amino acids to ribosomes
  • Anticodons of tRNA match codons on mRNA
  • Peptide bonds form between amino acids, creating a polypeptide
  • Translation happens at ribosomes in the cytoplasm
  • mRNA codons are read in triplets (three bases at a time)

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Related Documents

DNA Study Guide - Nucleic Acids PDF

Description

Explore the essentials of nucleic acids, focusing on DNA and RNA structures, their monomeric units, and the intricate process of DNA replication. Understand the significance of nucleotide components, base pairing, and enzyme functions in genetic information transfer. This quiz is perfect for students looking to deepen their understanding of molecular biology.

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