DNA Structure and Function
41 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What key information did Rosalind Franklin and Maurice Wilkins' X-ray crystallography contribute to Watson and Crick's DNA model?

  • Evidence suggesting the helical structure of DNA. (correct)
  • The precise atomic structure of deoxyribose sugar.
  • The specific sequence of nucleotide bases within the DNA molecule.
  • Confirmation of the presence of phosphate groups in DNA.

If a DNA strand has the sequence 5'-ATG-3', what would be the corresponding sequence on the complementary strand, considering the correct notation?

  • 3'-TAC-5' (correct)
  • 5'-TAC-3'
  • 3'-CAT-5'
  • 5'-CAT-3'

Which of the following aspects of the DNA structure primarily contributes to the storage of genetic information?

  • The deoxyribose-phosphate backbone.
  • The helical shape of the molecule.
  • The hydrogen bonds between complementary strands.
  • The sequence of nucleotide bases. (correct)

In the provided DNA structure schematic, what functional group is attached to the 5' carbon of the deoxyribose sugar?

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

Considering scientific disciplines, how did Watson and Crick's backgrounds contribute to their discovery?

<p>Watson's biology background allowed him to focus on the chemical properties of DNA, while Crick's physics expertise enabled them to model the physical structure. (C)</p> Signup and view all the answers

Which chemical feature is unique to ribonucleotides found in DNA compared to those found in RNA?

<p>Ribonucleotides in DNA contain a deoxyribose sugar lacking an oxygen on the 2' carbon. (B)</p> Signup and view all the answers

If a single strand of DNA has the sequence 5'-GATTACA-3', what would be the sequence of its complementary strand?

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

What maintains the double-stranded structure of DNA?

<p>Hydrogen bonds between complementary base pairs (A)</p> Signup and view all the answers

Which statement accurately describes the polarity of DNA strands within the double helix?

<p>One strand runs 5' to 3', while the complementary strand runs 3' to 5'. (B)</p> Signup and view all the answers

In DNA, guanine always pairs with cytosine, and adenine always pairs with thymine. What kind of bond facilitates these pairings?

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

In Griffith's experiment, what would be the expected outcome if living S strain Streptococcus pneumoniae were injected into a mouse?

<p>The mouse would develop pneumonia and die, as the S strain is pathogenic. (C)</p> Signup and view all the answers

What critical observation in Griffith's experiment led to the concept of transformation?

<p>A mixture of heat-killed S strain and living R strain bacteria caused disease in mice. (D)</p> Signup and view all the answers

In Griffith's experiment, if only heat-killed S strain cells are injected into a mouse, what is the expected result, and why?

<p>The mouse lives because the heat-killed S strain is no longer capable of causing infection. (B)</p> Signup and view all the answers

What is the most accurate interpretation of the term 'transformation' as it relates to Griffith's experiment?

<p>The genetic alteration of bacteria through the uptake of genetic material from dead bacteria. (C)</p> Signup and view all the answers

Based on the design and results of Griffith's experiment, what conclusion can be drawn about the nature of the 'transforming principle' at the time of the experiment?

<p>The transforming principle is a heritable substance. (E)</p> Signup and view all the answers

What is the most accurate definition of transformation in the context of bacterial genetics?

<p>The change in a bacterium's genotype and phenotype due to the assimilation of external DNA. (C)</p> Signup and view all the answers

What conclusion was drawn from Alfred Hershey and Martha Chase's experiment?

<p>DNA is the genetic material of a specific phage known as T2. (D)</p> Signup and view all the answers

Erwin Chargaff's analysis of DNA base composition revealed what key finding about different species?

<p>DNA composition varies from one species to another. (B)</p> Signup and view all the answers

According to Chargaff's rules, what relationship exists between the nitrogenous bases in DNA?

<p>The amount of adenine is approximately equal to the amount of thymine, and the amount of guanine is approximately equal to the amount of cytosine. (A)</p> Signup and view all the answers

If a species has 20% of its DNA composed of guanine, what percentage of its DNA is composed of adenine?

<p>30% (C)</p> Signup and view all the answers

What was the significance of Chargaff's rules prior to the discovery of the double helix structure of DNA?

<p>They made DNA a more credible candidate for the genetic material. (C)</p> Signup and view all the answers

What is the function of the tail fibers in a bacteriophage such as T2?

<p>To recognize and attach to the surface of a bacterial cell. (C)</p> Signup and view all the answers

Prior to the 1950s, what was already known about DNA?

<p>DNA is composed of nucleotides. (B)</p> Signup and view all the answers

Which combination of scientists is recognized for their direct contributions to the discovery of DNA's structure?

<p>Franklin, Wilkins, Watson, and Crick (D)</p> Signup and view all the answers

A scientist is studying a new virus with a mutation in its DNA repair system. Which of the following outcomes is MOST likely to occur?

<p>An increased likelihood of mutations in the viral genome (B)</p> Signup and view all the answers

During DNA replication, which enzyme is primarily responsible for proofreading and correcting errors?

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

A researcher is investigating the regulation of a specific gene. They observe increased levels of mRNA transcripts for this gene in response to a particular signaling molecule. This observation suggests that the signaling molecule is MOST likely acting as which of the following?

<p>An inducer of transcription (D)</p> Signup and view all the answers

Which of the following techniques is MOST appropriate for determining the expression levels of thousands of genes simultaneously in a cell?

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

A point mutation in a gene results in a codon changing from GAA to GAG. Both codons specify glutamic acid. What type of mutation is this?

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

If a DNA sequence is altered such that a codon now codes for a stop codon, what type of mutation is this called, and what effect will it have on the protein?

<p>Nonsense mutation, resulting in a truncated protein (B)</p> Signup and view all the answers

During which phase of the cell cycle does DNA replication occur?

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

Which diagnostic technique relies on the amplification of specific DNA sequences to detect the presence of a pathogen or genetic abnormality?

<p>Polymerase Chain Reaction (PCR) (A)</p> Signup and view all the answers

A new drug is designed to inhibit telomerase activity in cancer cells. What is the MOST likely outcome of this drug's action?

<p>Telomere shortening and eventual cell death (A)</p> Signup and view all the answers

If a DNA molecule is found to have 22% Adenine, what percentage of Cytosine would you expect to find?

<p>28% (B)</p> Signup and view all the answers

Which of the following distinguishes the 5' end from the 3' end of a DNA strand?

<p>The presence of a phosphate group attached to the 5' carbon of deoxyribose. (C)</p> Signup and view all the answers

If a mutation occurred causing thymine to bind with guanine, what would be the most likely result?

<p>A structural change in the DNA molecule. (D)</p> Signup and view all the answers

Which component of a nucleotide directly accounts for the genetic variation among DNA molecules?

<p>The nitrogenous base. (A)</p> Signup and view all the answers

Considering the structure of DNA, what would happen if a molecule lacked the sugar-phosphate backbone?

<p>The nitrogenous bases would not be able to pair correctly. (D)</p> Signup and view all the answers

How does the arrangement of the sugar-phosphate backbone contribute to the stability of the DNA molecule in an aqueous cellular environment?

<p>By positioning the hydrophilic sugar and phosphate groups on the exterior, shielding the hydrophobic bases. (A)</p> Signup and view all the answers

If research showed a new form of DNA with a consistently higher proportion of guanine and cytosine compared to adenine and thymine, what might be a likely consequence?

<p>Enhanced thermal stability due to stronger stacking interactions and more hydrogen bonds. (A)</p> Signup and view all the answers

A scientist is trying to synthesize a new DNA analog in the lab, but they want it to have weaker bonding than normal DNA. Which modification to the standard DNA structure would achieve this goal?

<p>Using nitrogenous bases with modified structures that only form one hydrogen bond. (D)</p> Signup and view all the answers

Flashcards

Deoxyribonucleotides

Building blocks of DNA; composed of a deoxyribose sugar, a phosphate group, and a nitrogenous base (A, T, C, G).

DNA Strand Polarity

DNA consists of two strands that run in opposite directions (5' to 3' and 3' to 5').

DNA Complementary Strands

The sequence of one DNA strand determines the sequence of the other; Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

Anti-Parallel Nature

The two DNA strands run in opposite directions to each other.

Signup and view all the flashcards

DNA Replication

The process of copying DNA to produce new DNA molecules.

Signup and view all the flashcards

Bacteriophage

Viruses that infect bacteria. They consist of DNA enclosed in a protective protein coat.

Signup and view all the flashcards

Griffith's Experiment

Experiment by Frederick Griffith involving Streptococcus pneumoniae. Demonstrates bacterial transformation.

Signup and view all the flashcards

Streptococcus pneumoniae

A bacterium that comes in two strains: Smooth (S) which is pathogenic, and Rough (R) which is not.

Signup and view all the flashcards

"S" (smooth) strain

The disease-causing strain of Streptococcus pneumoniae, characterized by a smooth outer capsule.

Signup and view all the flashcards

"R" (rough) strain

The non-disease-causing strain of Streptococcus pneumoniae; lacks a smooth outer capsule.

Signup and view all the flashcards

Transformation

A change in genotype and phenotype due to the assimilation of external DNA by a cell.

Signup and view all the flashcards

Hershey and Chase experiment

Identified DNA as the genetic material of a phage known as T2.

Signup and view all the flashcards

Chargaff's first observation

The base composition of DNA varies from one species to the next.

Signup and view all the flashcards

Chargaff's second observation

In any organism the amount of A=T, and the amount of G=C.

Signup and view all the flashcards

DNA composition variability

DNA varies from one species to another.

Signup and view all the flashcards

DNA polymer of nucleotides

DNA is made up of nucleotides.

Signup and view all the flashcards

Phage

A virus that infects bacteria.

Signup and view all the flashcards

Sugar-phosphate backbone

A structural component of DNA, composed of alternating sugar and phosphate groups.

Signup and view all the flashcards

5' end

The end of a DNA strand that terminates with a phosphate group attached to the 5' carbon of the deoxyribose sugar.

Signup and view all the flashcards

Nitrogenous base

Organic molecules with a nitrogen atom, act as the building blocks of DNA and RNA, forming the genetic code.

Signup and view all the flashcards

Thymine (T)

One of the four nitrogenous bases in DNA; pairs with adenine (A).

Signup and view all the flashcards

Adenine (A)

One of the four nitrogenous bases in DNA; pairs with thymine (T).

Signup and view all the flashcards

Cytosine (C)

One of the four nitrogenous bases in DNA; pairs with guanine (G).

Signup and view all the flashcards

DNA Strand ends (5' and 3')

The two ends of a DNA strand, defined by the location of the phosphate (5') or hydroxyl (3') group on deoxyribose.

Signup and view all the flashcards

Nucleic Acid Structure & Genome Organization

Describes the levels of DNA and RNA organization within a cell, including the arrangement of genetic material.

Signup and view all the flashcards

DNA Mutation & Repair

Alterations in the DNA sequence that can arise spontaneously or be induced by external factors. Includes point mutations, insertions, deletions and the body's mechanisms to correct them.

Signup and view all the flashcards

Genetic Information Flow & Regulation

The central dogma of molecular biology describes how genetic information flows from DNA to RNA to protein. This is crucial for cell behavior and function.

Signup and view all the flashcards

Molecular Techniques in Disease Management

Techniques used to analyze DNA, RNA, and proteins for diagnosing diseases, predicting their course, and guiding treatment decisions.

Signup and view all the flashcards

Team-Based Learning (TBL)

A type of assessment where students answer questions first individually and then again as a group, promoting discussion and deeper understanding.

Signup and view all the flashcards

Chargaff's Contributions

Experimental analysis by Erwin Chargaff which led to the finding that the amount of guanine is equal to cytosine and adenine is equal to thymine.

Signup and view all the flashcards

Contributions by Rosalind Franklin

The X-ray diffraction images generated by Rosalind Franklin played a pivotal role in deciphering the double helix structure of DNA.

Signup and view all the flashcards

Contributions by Maurice Wilkins

Maurice Wilkins shared the Nobel Prize with Watson and Crick for his work on the structure of DNA.

Signup and view all the flashcards

Contributions from Watson & Crick

James Watson and Francis Crick are credited with developing the first accurate model of the double helix structure of DNA.

Signup and view all the flashcards

Watson and Crick

The researchers who proposed the double helix structure of DNA in 1953.

Signup and view all the flashcards

X-ray crystallography

A technique used to determine the molecular structure of a crystal by analyzing how it scatters X-rays.

Signup and view all the flashcards

X-ray diffraction

Maurice Wilkins and Rosalind Franklin used this technique to study DNA structure.

Signup and view all the flashcards

Guanine (G)

A nitrogenous base that pairs with Cytosine (C) in DNA.

Signup and view all the flashcards

Study Notes

  • The Molecular Biology course (MPRM0107) is designed for Year 2 students, specifically MD1
  • The course spans a spring semester, offering 3 credit hours, including 2 hours of lectures and 1 hour of tutorial
  • Dr. Souad Al-Okla serves as the Course Coordinator

Course Goal and Description

  • Examines molecular processes within cells, emphasizing the structure, function, and regulation of nucleic acids
  • Introduces molecular biology techniques
  • Encompasses the structure, function, replication, damage, and repair of nucleic acids
  • Covers the control of gene expression, along with molecular and biochemical techniques for nucleic acid sequence analysis
  • Discusses the applications of these techniques in diagnosing, predicting, and managing human diseases

Learning Outcomes

  • Describe the structural levels of nucleic acids and genome organization
  • Describe different types of DNA mutation, their causes and consequences, and the role of DNA-repair systems
  • Explain the molecular events and enzymes involved in DNA replication
  • Discuss the flow of genetic information and how it is regulated in relation to cell behavior
  • Describe molecular techniques and their applications in diagnosing, predicting, and managing human diseases

Assessment Plan

  • The course uses summative and formative assessments to determine student grades
  • Summative assessments include an in-course exam (30%), a final exam (40%), and quizzes (7.5% each)
  • Continuous assessments include a presentation and concept map assignments
  • Self-Directed Learning (SDL) and Task-Based Learning (TBL) activities (5% each)

Assessment Dates

  • Quiz 1: February 20, 2025
  • In Course Exams: March 13, 2025
  • Quiz 2: April 22, 2025
  • Final Exams: May 15, 2025

The Structure of DNA

  • Students should recognize the contributions of Rosalind Franklin, Chargaff, Maurice Wilkins, Watson, and Crick toward unveiling DNA structure
  • Students should understand ribonucleotide biochemical structure and explain DNA structure including strands, polarity, base pairing, and anti-parallel nature

Genetic Information

  • Base pairs in DNA are nitrogenous bases in the double helix, held together by hydrogen bonds
  • Adenine (A) pairs with Thymine (T) using two hydrogen bonds; Guanine (G) pairs with Cytosine (C) using three
  • DNA can pass information by replication.
  • Information coded in the sequence of base pairs in DNA is passed to molecules of RNA.
  • Information in RNA is passed to proteins.

Nucleic Acids

  • DNA is the substance of inheritance
  • Hereditary information is encoded in DNA's chemical language
  • DNA directs the development of different trait types

DNA's Discovery

  • Early 20th-century biologists faced the challenge of identifying inheritance molecules
  • DNA's role in heredity was first studied in bacteria and viruses infecting them (bacteriophages)

Griffith's Experiment

  • Frederick Griffith's experiment with Streptococcus pneumoniae demonstrated bacterial transformation
  • Living R bacteria transformed into pathogenic S bacteria via a heritable substance from dead S cells

DNA as Genetic Material

  • DNA, not protein, carries heritable information
  • Transformation requires DNA
  • DNA is the genetic material of the cell
  • Viruses infecting bacteria (bacteriophages) have DNA as their genetic material

Hershey and Chase Experiment

  • Radioactive phosphorus-32P labeled DNA and radioactive sulfur-35S labeled proteins
  • Viruses infected E. coli, shearing off viral heads and centrifuging
  • Infected bacteria contained 32P but not 35S, verifying DNA is a phage's genetic material

Chargaff's Analysis

  • Erwin Chargaff analyzed DNA base composition from different organisms.
  • Chargaff reported that DNA composition varies from one species to the next

Chargaffs Rule

  • Adenine number ≈ Thymine number (T% = A%)
  • Guanine number ≈ Cytosine number (G% = C%)
  • Guanine, cytosine, adenine, and thymine bases vary among species
  • These pairings remained unexplained until the discovery of the double helix

DNA Structure

  • In the 1950s, DNA was already known as a nucleotide polymer
  • Polynucleotides are synthesized when adjacent nucleotides are joined by covalent bonds called phosphodiester linkages
  • A sugar-phosphate backbone has nitrogenous bases as appendages
  • Distinct free ends of the polymer are referred to as the 5' and 3' ends
  • Watson and Crick deduced that DNA was a double helix

Rosalind Franklin's Contribution

  • Maurice Wilkins and Rosalind Franklin used X-ray crystallography to study DNA's molecular structure
  • Franklin produced an DNA molecule image using X-ray crystallography techniques

Watson and Crick Model

  • Franklin concluded DNA has two antiparallel sugar-phosphate backbones, with nitrogenous bases paired within
  • Nitrogenous bases pair specifically: adenine with thymine, cytosine with guanine

Base Pairing Specificity

  • Base pairs form hydrogen bonds
  • Adenine and thymine form two bonds
  • Cytosine and guanine form three bonds

DNA Structure Details

  • Purine + purine is too wide
  • Pyrimidine + pyrimidine is too narrow
  • Purine + pyrimidine width is consistent with X-ray data

Base Pairings

  • Adenine forms two hydrogen bonds with thymine only
  • Guanine forms three hydrogen bonds with cytosine only
  • Cellular DNA molecules have two complementary polynucleotide strands
  • These strands are connected with hydrogen bonds, spiraling around an axis to form a double helix

Summary of DNA

  • DNA comprises four nucleotide building blocks
  • Nucleotides are made of sugar-phosphate covalently linked to a base
  • Nucleotides are covalently linked into polynucleotide chains
  • The DNA molecule is composed of two DNA strands
  • DNA is wound into a double helix

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Molecular Biology (MPRM 0107) PDF - National University Exam

Description

Explore DNA structure and function. Understand the contributions of Rosalind Franklin and Maurice Wilkins, complementary base pairing, and unique chemical features of DNA and RNA. This also covers the polarity of DNA strands within the double helix.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser