Nucleic Acids and DNA Replication
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What is the function of the enzyme primase in DNA replication?

  • Primase initiates DNA synthesis by joining nucleotides and creating a short RNA primer. (correct)
  • Primase separates the two strands of DNA by cutting and rejoining the sugar-phosphate backbone.
  • Primase unwinds the DNA double helix, breaking hydrogen bonds between the strands.
  • Primase adds nucleotides to the 3' end of a pre-existing chain, replicating the original strands of DNA.

During DNA replication, what is the role of the lagging strand?

  • The lagging strand doesn't require a primer for replication, unlike the leading strand.
  • The lagging strand is replicated continuously in the 5' to 3' direction, following the replication fork.
  • The lagging strand is formed away from the replication fork and is copied in segments called Okazaki fragments. (correct)
  • The lagging strand is involved in the synthesis of telomeres, protecting the ends of chromosomes from degradation.

What is the difference between leading strand and lagging strand DNA replication?

  • The leading strand requires more enzymes than the lagging strand to complete replication.
  • The leading strand is replicated in the 5' to 3' direction while the lagging strand is replicated in the 3' to 5' direction.
  • The leading strand utilizes RNA primers while the lagging strand doesn't require them.
  • The leading strand is synthesized continuously while the lagging strand is synthesized discontinuously in fragments. (correct)

What is the function of telomeres?

<p>Telomeres act as end caps of DNA, protecting the ends from degradation during replication. (B)</p> Signup and view all the answers

What is the primary function of mRNA in protein synthesis?

<p>mRNA carries genetic information from the nucleus to the ribosomes for protein production. (B)</p> Signup and view all the answers

What is the role of tRNA during translation?

<p>tRNA carries amino acids to the ribosomes, matching them to the mRNA codons. (A)</p> Signup and view all the answers

What is the significance of the start codon AUG in translation?

<p>AUG initiates protein translation, signifying the beginning of a polypeptide chain. (C)</p> Signup and view all the answers

What is the central dogma of molecular biology?

<p>DNA is transcribed into RNA, which is then translated into proteins. (C)</p> Signup and view all the answers

What is the main difference between a lytic and lysogenic viral cycle?

<p>The lytic cycle destroys the host cell immediately by releasing new viruses, while the lysogenic cycle replicates the viral genome within the host without immediately destroying it. (C)</p> Signup and view all the answers

What are plasmids in the context of genetic engineering?

<p>Plasmids are small circular DNA molecules found primarily in bacteria, often used as vectors to carry foreign genes into other organisms. (C)</p> Signup and view all the answers

During DNA replication, which of the following is TRUE about the lagging strand?

<p>It is synthesized discontinuously in the 5' to 3' direction. (A)</p> Signup and view all the answers

What is the role of the enzyme helicase in DNA replication?

<p>It unwinds the DNA double helix. (D)</p> Signup and view all the answers

Which of the following best describes the role of telomeres in DNA replication?

<p>They are nonsensical sequences that protect the ends of chromosomes from degradation. (C)</p> Signup and view all the answers

Which of the following accurately describes the function of tRNA?

<p>It carries amino acids to the ribosomes where they are incorporated into proteins. (B)</p> Signup and view all the answers

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

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

Which of the following accurately describes the difference between a lysogenic and a lytic phage cycle?

<p>In a lysogenic cycle, the phage DNA integrates into the host genome, while in a lytic cycle, the phage DNA replicates independently. (B)</p> Signup and view all the answers

What is the role of plasmids in genetic engineering?

<p>Both B and C are correct. (A)</p> Signup and view all the answers

What is the function of the enzyme reverse transcriptase?

<p>It synthesizes DNA from an RNA template. (A)</p> Signup and view all the answers

How does the genetic code differ from the codon?

<p>The genetic code is a complete set of rules determining how codons are used to specify amino acids, whereas a codon is a three-nucleotide sequence. (C)</p> Signup and view all the answers

What is the primary role of DNA polymerase in DNA replication?

<p>It adds nucleotides to the 3' end of a growing DNA strand, building new DNA molecules. (B)</p> Signup and view all the answers

What is the relationship between DNA, genes, and chromosomes?

<p>Genes are specific segments of chromosomes, and chromosomes are composed of DNA. (A)</p> Signup and view all the answers

What is the significance of the 5' to 3' directionality of DNA?

<p>It determines the direction of DNA replication, with nucleotides being added only to the 3' end. (B)</p> Signup and view all the answers

Why is the lagging strand replicated in a discontinuous manner, creating Okazaki fragments?

<p>The lagging strand is synthesized in the opposite direction of the unwinding of the DNA helix, requiring a discontinuous process. (B)</p> Signup and view all the answers

What is the function of telomerase in DNA replication?

<p>It adds repetitive DNA sequences to the ends of chromosomes, preventing the loss of genetic information during replication. (D)</p> Signup and view all the answers

What is the major difference between mRNA and tRNA?

<p>mRNA carries the genetic code from DNA to the ribosome, while tRNA carries amino acids to the ribosome. (D)</p> Signup and view all the answers

What is the role of the ribosome in translation?

<p>Ribosomes are the sites of protein synthesis, where amino acids are linked together based on the mRNA code. (B)</p> Signup and view all the answers

What is the significance of the stop codon in translation?

<p>The stop codon signals the end of translation, terminating the process of protein synthesis. (A)</p> Signup and view all the answers

What is the difference between a lytic and lysogenic viral lifecycle?

<p>Lytic viruses replicate immediately and destroy the host cell, while lysogenic viruses integrate their genome into the host genome and replicate with the host. (B)</p> Signup and view all the answers

What type of RNA carries information from DNA to be translated into a peptide sequence?

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

What are Okazaki fragments?

<p>Short segments of DNA formed on the lagging strand (B)</p> Signup and view all the answers

What molecule is primarily responsible for unwinding the DNA double helix during replication?

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

Which statement accurately describes reverse transcription in retroviruses?

<p>It synthesizes DNA from RNA. (A)</p> Signup and view all the answers

What initiates the process of transcription in the cell?

<p>Transcription initiation complex (C)</p> Signup and view all the answers

What best describes the role of telomerase in DNA replication?

<p>It helps maintain the length of telomeres. (B)</p> Signup and view all the answers

During DNA replication, which strand is synthesized continuously?

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

What is the function of ligase during DNA replication?

<p>To glue together Okazaki fragments (A)</p> Signup and view all the answers

Which of the following explains the function of the ribosome in protein synthesis?

<p>It reads mRNA to create a protein. (A)</p> Signup and view all the answers

Which nucleotide sequence is complementary to the DNA strand TACCGAC?

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

Flashcards

DNA Structure

DNA is composed of nucleotides made of sugar, phosphate, and a nitrogenous base.

Genes

Genes are segments of DNA that encode physical traits and characteristics unique to an individual.

DNA Replication

DNA replication occurs semi-conservatively, producing two strands, each with one original and one new strand.

Leading Strand

The leading strand is synthesized continuously in the 5' to 3' direction towards the replication fork.

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Lagging Strand

The lagging strand is synthesized in short segments called Okazaki fragments away from the replication fork.

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Okazaki Fragments

Okazaki fragments are short DNA segments produced on the lagging strand during DNA replication.

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RNA Transcription

Transcription is the process where DNA is copied to produce messenger RNA (mRNA).

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mRNA Processing

Before leaving the nucleus, mRNA undergoes processing, including adding a GTP cap and poly-A tail.

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Translation

Translation is the process by which ribosomes read mRNA to synthesize proteins with the help of tRNA.

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Mutation

A mutation is a change in the DNA sequence that can lead to variation in traits.

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Chromosomes

Chromosomes are structures that carry DNA, crucial for maintaining genetic information.

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Semiconservative Replication

DNA replicates semiconservatively, making two strands: one old and one new.

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Primase

Primase synthesizes a short RNA primer for DNA polymerase to begin replication.

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DNA Polymerase

DNA polymerase adds nucleotides to the growing DNA strand during replication.

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Leading Strand Direction

The leading strand is synthesized continuously towards the replication fork in the 5' to 3' direction.

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Lagging Strand Segments

The lagging strand is synthesized in fragments known as Okazaki fragments.

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Telomeres

Telomeres are protective ends of chromosomes that shorten with cell division.

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Transcription Initiation

Transcription begins when RNA polymerase binds to DNA and unwinds it to read the gene.

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Codons

Codons are sequences of three nucleotides on mRNA that correspond to a specific amino acid.

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Retroviruses

Retroviruses contain RNA and use reverse transcription to integrate into the host's DNA.

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DNA Structure Components

DNA is made of nucleotides that include a sugar, phosphate, and nitrogenous base.

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Role of Genes

Genes are segments of DNA responsible for unique traits in organisms.

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DNA Replication Process

DNA replication is semi-conservative, using one old strand to create a new strand.

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Leading Strand Characteristics

The leading strand is synthesized continuously towards the replication fork in the 5' to 3' direction.

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Lagging Strand Characteristics

The lagging strand is synthesized discontinuously in segments called Okazaki fragments, away from the fork.

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Primase Function

Primase synthesizes a short RNA primer that starts the DNA replication process.

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Okazaki Fragment Length

Okazaki fragments are about 100-200 nucleotides long and are joined by ligase during replication.

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Role of Telomeres

Telomeres are repetitive sequences at the end of chromosomes that protect genetic data and shorten with replication.

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RNA Transcription Overview

Transcription is the process where DNA is copied to produce messenger RNA (mRNA).

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Translation Process

During translation, ribosomes read mRNA codons to assemble amino acids into a protein.

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DNA Replication Fork

The point where DNA double helix is unwound during replication.

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Helicase

An enzyme that unwinds DNA by breaking hydrogen bonds between strands.

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Polymerase Direction

DNA polymerase adds nucleotides to the 3' end of a DNA strand.

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Leading Strand Synthesis

A strand synthesized continuously toward the replication fork during DNA replication.

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Lagging Strand Synthesis

A strand synthesized in short fragments away from the replication fork during DNA replication.

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Messenger RNA (mRNA)

RNA that carries genetic information from DNA to the ribosome for translation.

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Study Notes

Nucleic Acids

  • Chromosomes carry DNA, which is responsible for building and maintaining human structure.
  • Genes are segments of DNA, determining unique traits.
  • Nucleic acids (DNA and RNA) are large, complex molecules composed of nucleotides (sugar, phosphate, nitrogenous base).
  • DNA structure: double helix, antiparallel strands (5' to 3' and 3' to 5').
  • Chargaff's rule: A=T and C=G (base pairing).
  • Purines (double-ring): Adenine (A) and Guanine (G).
  • Pyrimidines (single-ring): Cytosine (C) and Thymine (T) in DNA, Uracil (U) in RNA.
  • RNA structure: single-stranded.
  • Nucleotides in DNA: deoxyribose sugar
  • Nucleotides in RNA: ribose sugar

DNA Replication

  • DNA replicates before cell division, each strand serving as a template.
  • Semiconservative replication: one original strand and one new strand in each new DNA molecule.
  • Leading strand: synthesized continuously in the 5' to 3' direction.
  • Lagging strand: synthesized discontinuously in Okazaki fragments, then joined by DNA ligase.
  • Enzymes: helicase (unwinds DNA), topoisomerase (relieves strain), single-strand binding proteins (prevent re-annealing), DNA polymerase (adds nucleotides), primase (synthesizes RNA primers), DNA ligase (joins Okazaki fragments), and DNA polymerase III (crucial for extending new DNA strands).
  • 5' and 3' refer to the carbon numbers on the sugar in the nucleotides.
  • Replication fork: Y-shaped region where DNA strands separate during replication.

RNA

  • Types of RNA: mRNA (messenger), tRNA (transfer), rRNA (ribosomal).
  • Transcription: DNA is copied to mRNA.
  • mRNA processing: 5' cap and 3' poly-A tail added, introns removed (splicing), creating mature mRNA. A 5' GTP cap and 3' poly-A tail are important modifications for mRNA stability and ribosome binding.
  • Translation: mRNA is decoded to produce a polypeptide chain.
  • Ribosomes: site of protein synthesis.
  • tRNA carries amino acids to ribosomes.
  • RNA polymerase is the enzyme responsible for transcription.

Mutations

  • Mutations are changes in DNA sequence.
  • Types: insertion, deletion, substitutions (silent, missense, nonsense).
  • Frameshift mutations: alter the reading frame (e.g., insertion, deletion).
  • Mutations can be caused by mutagenic agents such as radiation, chemicals, or errors during replication/repair.
  • Point mutations - substitutions, insertions, deletions.
  • Types of mutations - affect proteins, cause diseases, impact protein function.
  • Mutations can occur spontaneously or due to mutagens. Errors during replication, exposure to harmful radiation or chemicals can all lead to mutations.

Gene Expression

  • Transcription: DNA to RNA.
  • Translation: RNA to polypeptide chain.
  • Genetic regulation: control of gene expression.

Viruses

  • Viruses: non-living infectious agents.
  • Parts: capsid, nucleic acid (DNA or RNA), possibly an envelope.
  • Types: bacteriophages, retroviruses.
  • Replication cycles: lytic (immediate replication, cell lysis), lysogenic (viral DNA integrates into host DNA).
  • Retroviruses have RNA as their genetic material. This RNA is reverse transcribed into DNA, which is integrated into the host genome.
  • Telomeres: repetitive nucleotide sequences at the ends of chromosomes to protect them during replication.

Bacterial Genetics

  • Circular DNA in the nucleoid region.
  • Replication: bi-directional, primarily by binary fission.
  • Transformation: acquiring DNA from the environment.
  • Plasmids: small, circular DNA molecules.
  • Important in Genetic Engineering.
  • Bacterial genetics also includes conjugation (transfer of DNA between bacteria) and transduction (transfer of DNA via a virus).
  • Transduction: transfer of genetic material from one cell to another via a bacteriophage.
  • In bacteria, transformation, transduction and conjugation all involve DNA transfer to alter the genetic makeup of the bacteria.
  • Okazaki fragments: short DNA fragments synthesized on the lagging strand during DNA replication.
  • Telomeres: repeated nucleotide sequences at the ends of linear chromosomes, critical for stability.

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DNA Notes Unit 5 PDF

Description

Explore the fascinating world of nucleic acids, including the structure of DNA and RNA, their roles in genetics, and the process of DNA replication. This quiz delves into key concepts such as Chargaff's rule, the distinction between leading and lagging strands, and the enzymes involved in replication.

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