Introduction to Molecular Genetics: DNA Structure
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Questions and Answers

What is the primary purpose of DNA replication?

  • To create energy for cell functions
  • To ensure each new cell has a copy of DNA (correct)
  • To convert DNA into amino acids
  • To transport DNA to ribosomes

Which enzyme is responsible for breaking the hydrogen bonds that link nitrogenous bases during DNA replication?

  • DNA helicase (correct)
  • DNA ligase
  • DNA polymerase
  • RNA polymerase

Why is DNA replication described as semi-conservative?

  • One strand is from the original and the other is newly synthesized (correct)
  • The process occurs in the cytoplasm
  • Both strands are completely new
  • Only a portion of the DNA is replicated

What is the first step in the flow of genetic information according to the Central Dogma?

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

In which part of the cell does DNA reside?

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

What plays the role of messenger in transporting DNA instructions to the ribosomes?

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

How does DNA replication help reduce copy errors?

<p>By always keeping one half of the old strand (B)</p> Signup and view all the answers

What becomes of the product of transcription?

<p>It is a single strand of RNA (B)</p> Signup and view all the answers

How much DNA does an average human cell contain?

<p>3 meters (D)</p> Signup and view all the answers

What are the roles of DNA polymerases during DNA replication?

<p>To add nucleotides according to base pairing rules (A)</p> Signup and view all the answers

What forms the main structure of the DNA double helix?

<p>Sugar-phosphate backbones coiling around each other (D)</p> Signup and view all the answers

Which base pairs correctly represent the Base Pair Rule in DNA?

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

How many nucleotides complete one full turn of the DNA double helix?

<p>10 nucleotides (A)</p> Signup and view all the answers

What is the main component that makes up DNA?

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

What is unique about the structure of prokaryotic chromosomes?

<p>They are circular and supercoiled (D)</p> Signup and view all the answers

What distinguishes RNA from DNA?

<p>RNA substitutes uracil for thymine (B)</p> Signup and view all the answers

Which type of bond connects the nitrogen base to the sugar in a nucleotide?

<p>b-N-glycosidic linkage (A)</p> Signup and view all the answers

What type of structure do purines have?

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

In terms of hydrogen bonding, how many hydrogen bonds are formed between adenine and thymine?

<p>2 hydrogen bonds (B)</p> Signup and view all the answers

Which of the following nitrogen bases is classified as a pyrimidine?

<p>Cytosine (B), Thymine (C)</p> Signup and view all the answers

What is the diameter of the DNA double helix?

<p>2.0 nm (B)</p> Signup and view all the answers

What configuration do the two strands of DNA have concerning their directionality?

<p>The strands run antiparallel (A)</p> Signup and view all the answers

What is the covalent bond that links the sugar and the phosphoryl group in a nucleotide called?

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

What is created when portions of RNA undergo base pairing?

<p>A secondary structure (D)</p> Signup and view all the answers

Which components make up a nucleotide?

<p>Phosphate, deoxyribose sugar, and nitrogen base (B)</p> Signup and view all the answers

How do the two strands of DNA interact with each other?

<p>They twist around each other to form a double helix (B)</p> Signup and view all the answers

What is the ring structure designation for the sugar found in DNA?

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

Which of the following pairs are both purines?

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

What is the primary function of DNA in cells?

<p>To store genetic information (C)</p> Signup and view all the answers

Which nitrogenous base has a single ring structure?

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

Which of the following statements best describes a gene?

<p>A segment of DNA that codes for a protein (D)</p> Signup and view all the answers

What are the building blocks of proteins?

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

Who were the key contributors to the discovery of the DNA double helix structure?

<p>James Watson and Francis Crick (A)</p> Signup and view all the answers

Which of the following best describes the role of proteins in the body?

<p>They perform various functions including structural roles, chemical reactions, and transport. (D)</p> Signup and view all the answers

What is a nucleotide composed of?

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

What type of sugar is found in RNA nucleotides?

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

What is the significance of Rosalind Franklin's work in DNA research?

<p>Her X-ray photos provided critical insight into DNA structure. (D)</p> Signup and view all the answers

Why is the study of DNA considered vital for medical advances?

<p>It enables disease detection, treatment, and prevention. (B)</p> Signup and view all the answers

Which of the following accurately describes chromosomes?

<p>Composed of DNA and proteins. (D)</p> Signup and view all the answers

Flashcards

Genetics

The study of genes and heredity.

Trait

An inherited characteristic determined by genes.

Gene

A segment of DNA that codes for a protein, which determines a trait.

DNA

Deoxyribonucleic Acid, molecule that stores genetic information.

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Chromosome

A structure made of DNA that carries genetic information.

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Nucleotide

The basic building block of DNA and RNA.

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Protein

A molecule made of amino acids that carries out many cellular functions.

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Amino Acid

Building blocks of proteins.

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Double Helix

The structure of DNA, resembling a twisted ladder.

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Purine/Pyrimidine

Types of nitrogenous bases found in DNA and RNA.

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Phosphate

Part of a nucleotide, often involved in chemical reactions.

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Deoxyribose

The sugar found in DNA nucleotides.

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Nitrogenous base

Molecule with nitrogen, found in DNA nucleotides; crucial for base pairing.

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Purine

Double-ring nitrogenous base (Adenine & Guanine).

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Pyrimidine

Single-ring nitrogenous base (Cytosine & Thymine).

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Adenine (A)

A purine nitrogenous base.

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Thymine (T)

A pyrimidine nitrogenous base.

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DNA strand

A long chain of nucleotides.

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DNA double helix

Two strands of DNA wound around each other.

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Cell division reason

Cells divide for growth or reproduction of an organism.

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DNA replication goal

Every new cell needs a copy of DNA, because it's the blueprint for building and running a cell.

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What does DNA replication use?

Enzymes like helicases unwind and separate the DNA strands, while polymerases add complementary nucleotides.

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What is semi-conservative replication?

DNA replication keeps one half of the original DNA strand in each new copy.

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Why is semi-conservative replication good?

It reduces errors during DNA replication, ensuring precise copies are made.

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How does DNA structure help replication?

The DNA double helix structure allows enzymes to 'read' one strand and add complementary bases to build a new strand.

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What does semiconservative replication result in?

A new DNA molecule with one original strand and one newly synthesized strand.

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What is the Central Dogma?

The flow of genetic information goes from DNA to RNA to protein, in a one-way direction.

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What is transcription?

The process of copying DNA into RNA.

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What is translation?

The process of converting RNA into protein.

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What holds base pairs together?

Hydrogen bonds connect the nitrogenous bases of the DNA strands, forming the rungs of the DNA ladder.

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Base Pair Rule

Adenine (A) always pairs with Thymine (T), while Cytosine (C) always pairs with Guanine (G).

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How many H bonds between A-T?

Adenine and Thymine form 2 hydrogen bonds.

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How many H bonds between C-G?

Cytosine and Guanine form 3 hydrogen bonds.

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Complementary Strands

The sequence of bases on one DNA strand dictates the sequence of bases on the other strand following the base pairing rule.

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Antiparallel Strands

The two DNA strands run in opposite directions, with one strand oriented 5' to 3' and the other 3' to 5'.

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Prokaryotic Chromosome

Circular DNA molecule found in prokaryotic cells, which is supercoiled and forms a structure called the nucleoid.

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Eukaryotic Chromosome Structure

Eukaryotic DNA is packaged around histone proteins, forming nucleosomes, then further coiled into higher-order structures.

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RNA structure

RNA is a single-stranded nucleotide chain containing ribose sugar and uracil (U) instead of thymine (T).

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Base Pairing in RNA

Like DNA, RNA can also form base pairs, with uracil (U) pairing with adenine (A), and guanine (G) pairing with cytosine (C).

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Study Notes

Introduction to Molecular Genetics: DNA and RNA Structure

  • Molecular genetics is the study of genes and heredity
  • DNA and RNA are crucial molecules in this field
  • DNA is often called the blueprint of life
  • DNA stores genetic information within cells
  • DNA contains instructions for making proteins within the cell
  • Chromosomes are composed of DNA
  • DNA is a polymer composed of repeating subunits called nucleotides
  • DNA has two long strands that twist around each other in a double helix

DNA Structure

  • DNA is a Deoxyribonucleic Acid
  • DNA is composed of a chain of nucleotides
  • Each nucleotide consists of a phosphate, a deoxyribose sugar and a nitrogenous base
  • The sides of DNA's ladder structure are composed of alternating phosphate and sugar molecules, creating a sugar-phosphate backbone
  • DNA two strands are held together by hydrogen bonds between the nitrogenous bases
  • Adenine bonds to Thymine (A-T) and Guanine bonds to Cytosine (G-C)

Nucleotide Structure

  • Nucleotides are the monomer units of DNA
  • Nucleotides consist of a nitrogen-containing heterocyclic base (purine or pyrimidine), a five-carbon sugar (deoxyribose), and a phosphate group
  • Purine bases include: adenine and guanine
  • Pyrimidine bases include: thymine and cytosine
  • DNA and RNA are long polymers
  • The sugar ring of the nucleotide is numbered using a prime system (e.g., 1', 2', 3')

Base Pairing Rule

  • Adenine pairs with Thymine (A-T) with two hydrogen bonds
  • Cytosine pairs with Guanine (G-C) with three hydrogen bonds

Nitrogenous Bases

  • There are four nitrogenous bases in DNA: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)
  • These bases form the rungs of the DNA ladder, connecting the two strands of DNA
  • The sequence of bases in DNA is what determines the genetic code
  • The ATCG bases contain endless combinations that make up the complex genetic information

RNA Structure

  • RNA is a Ribonucleic Acid molecule
  • RNA consists of a single strand of nucleotides
  • RNA's sugar is ribose, not deoxyribose
  • RNA's nitrogenous base, uracil (U), replaces thymine (T) in DNA.

DNA Replication

  • DNA replication is semi-conservative
  • In DNA replication, enzymes unwind and separate the double helix, and add complementary nucleotides to exposed strands
  • The result is two exact copies of the original DNA molecule
  • Each new double helix is composed of one original DNA strand and one new strand

Prokaryotic Chromosomes

  • Prokaryotes contain one chromosome, which is a circular supercoiled DNA molecule.
  • Prokaryotic DNA is located in an area called the nucleoid.

Eukaryotic Chromosomes

  • Eukaryotes have multiple linear chromosomes
  • Chromosomes are enclosed within a nuclear membrane
  • Chromosomes consist of organized structures called nucleosomes

Information Flow in Biological Systems

  • The Central Dogma describes the flow of genetic information: DNA to RNA to protein.
  • Transcription is the process where a single DNA strand serves as a template for RNA synthesis
  • Translation converts information from nucleic acid language (nitrogenous bases) to protein language (amino acids).
  • DNA provides the blueprint for building proteins, but proteins are built in the cytoplasm

Translation

  • DNA is located in the nucleus
  • DNA instructions are transported to the ribosomes in the cytoplasm via messenger RNA (mRNA)
  • Ribosomes make proteins using the information provided by mRNA
  • mRNA carries the instructions for building proteins from the DNA

DNA by the Numbers

  • Each human cell contains approximately three meters of DNA
  • The average human body has approximately 300 trillion cells
  • The total DNA in an average human body is sufficient to stretch from Earth to the sun over 400 times.
  • DNA has an extremely small diameter

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DNA and RNA Structure PDF

Description

Explore the fundamental concepts of molecular genetics with a focus on the structure of DNA and RNA. Understand how DNA serves as the blueprint of life, its composition, and the importance of nucleotides in genetic information storage and protein synthesis. This quiz delves into the molecular architecture of DNA, including its double helix formation.

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