Genetics and Nucleotides Overview
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Questions and Answers

What is one of the main functions of cyclic nucleotide monophosphates?

  • Structure formation
  • DNA replication
  • Cell signaling (correct)
  • Energy storage

Which of the following is an example of a nucleotide triphosphate?

  • Coenzyme A
  • cAMP
  • GTP (correct)
  • NAD

What role do coenzymes like Coenzyme A and NAD play in metabolism?

  • Form DNA structures
  • Facilitate reactions (correct)
  • Act as cell signaling molecules
  • Provide energy storage

How do nucleotide triphosphates function in relation to diphosphate forms?

<p>By conversion to and from diphosphate form (B)</p> Signup and view all the answers

Which of the following aspects is NOT included in the summary of knowledge about nucleotides and DNA?

<p>Chromosome function in protein synthesis (B)</p> Signup and view all the answers

What is the primary function of genes in genetics?

<p>To encode biological information (C)</p> Signup and view all the answers

Which of the following best describes the role of genetic material?

<p>It must contain complex information and replicate faithfully. (C)</p> Signup and view all the answers

What was the significant conclusion drawn from Avery et al.'s experiments with S.pneumoniae bacteria?

<p>R bacteria can transform when mixed with S bacteria. (A)</p> Signup and view all the answers

Which component of chromatin was first debated as the genetic material before the truth was realized in 1944?

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

What discovery related to genetic material was made around 1869?

<p>Nucleic acid was found in the nucleus (B)</p> Signup and view all the answers

What should be considered when identifying genetic material?

<p>Its requirement to encode the phenotype. (C)</p> Signup and view all the answers

Why was the tetranucleotide theory misleading about the genetic material?

<p>It suggested nucleic acids are simple units. (D)</p> Signup and view all the answers

Which of the following statements about DNA is incorrect?

<p>DNA is not involved in encoding the phenotype. (D)</p> Signup and view all the answers

What type of bonds link the nucleotides in the sugar-phosphate backbone of DNA?

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

Which statement about base pairing in DNA is accurate?

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

What property of DNA allows it to serve as a template for replication?

<p>Complementary base pairing (C)</p> Signup and view all the answers

Which of the following pairs of bases is linked by three hydrogen bonds?

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

What is true about the strands of DNA?

<p>They are complementary and antiparallel (B)</p> Signup and view all the answers

What aspect of DNA structure allows it to encode complex genetic information?

<p>The long sequences of nucleotide 'letters' (C)</p> Signup and view all the answers

Which type of structure is defined as the arrangement of the DNA double helix?

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

The sugar-phosphate backbone of DNA serves which primary function?

<p>Providing structural stability (B)</p> Signup and view all the answers

What type of bond creates the torsional force in a DNA molecule?

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

What is the structure of eukaryotic DNA primarily packed into?

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

How many base pairs are approximately found in a human chromosome?

<p>3.2 billion base pairs (D)</p> Signup and view all the answers

What structure is used to package DNA in eukaryotic cells?

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

Which of the following describes the nature of prokaryotic DNA?

<p>Circular and single chromosome (C)</p> Signup and view all the answers

What is a characteristic feature of the double helix of DNA?

<p>Presence of major and minor grooves (B)</p> Signup and view all the answers

Which of the following best describes a nucleosome?

<p>DNA wrapped around histone proteins (D)</p> Signup and view all the answers

What is the approximate length of the bacterial chromosome in E. coli compared to the cell size?

<p>1000 times longer (C)</p> Signup and view all the answers

What is the structure of chromatin during M-phase?

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

What characterizes euchromatin?

<p>It includes transcriptionally active regions. (D)</p> Signup and view all the answers

Which type of DNA is found in the cytoplasm of prokaryotes?

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

What is the primary function of mitochondrial DNA in eukaryotic cells?

<p>Encoding enzymes for oxidative phosphorylation (D)</p> Signup and view all the answers

What did Chargaff demonstrate about DNA in 1948?

<p>DNA has fixed ratios of adenine to thymine and guanine to cytosine. (D)</p> Signup and view all the answers

Which pair of scientists is credited with elucidating the structure of DNA as a double helix?

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

What is a characteristic of heterochromatin?

<p>It includes centromeres and telomeres. (C)</p> Signup and view all the answers

During which phase of the cell cycle does chromatin condense tightly?

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

What is the role of a nucleotide in the structure of DNA?

<p>It acts as a repeating unit that forms the DNA polymer. (C)</p> Signup and view all the answers

What type of bond joins nucleotides together in a DNA strand?

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

What role does non-coding DNA play in the genome?

<p>It serves structural roles and may regulate gene expression. (A)</p> Signup and view all the answers

What type of DNA is found in some bacterial cells and may encode traits like drug resistance?

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

What is the significance of the 'antiparallel' nature of DNA strands?

<p>It enables the pairing of complementary bases. (A)</p> Signup and view all the answers

Which statement best describes a purine?

<p>Purines are one of the two categories of nitrogenous bases. (D)</p> Signup and view all the answers

What is the maximum length variation for DNA chains mentioned in the content?

<p>A few thousand nucleotides to hundreds of millions of nucleotides. (A)</p> Signup and view all the answers

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

<p>A nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. (B)</p> Signup and view all the answers

Flashcards

Nucleic Acids

Large biological molecules that store and transmit genetic information, made of nucleotides.

Nucleotides

The building blocks of nucleic acids; each has a sugar, a phosphate, and a base.

DNA Structure

A double helix; two strands of nucleotides wound around each other.

Genetics

The study of heredity, or how traits are passed from parents to offspring.

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Phenotype

The observable traits of an organism, resulting from its genes and environment.

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Chromatin

Complex of DNA and proteins that forms chromosomes within the nucleus.

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Avery et al. experiment

Experiment that demonstrated DNA is the genetic material, not protein.

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Genetic Material

DNA, the molecule that carries the hereditary information.

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DNA Nucleotide Composition

DNA contains four specific nitrogenous bases (adenine, guanine, cytosine, and thymine) in fixed ratios.

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Chargaff's Rule

DNA has equal amounts of adenine (A) and thymine (T), and equal amounts of guanine (G) and cytosine (C).

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DNA Polymer

A long chain of nucleotides joined together by phosphodiester bonds.

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Purine

A type of nitrogenous base found in DNA (adenine and guanine).

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Pyrimidine

A type of nitrogenous base found in DNA (cytosine and thymine).

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Avery, MacLeod, and McCarty Experiment

A 1944 experiment demonstrating that DNA carries genetic information, not protein.

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Covalent bond

A strong chemical bond formed by the sharing of electron pairs between atoms.

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5' and 3' ends

The two distinct ends of a nucleotide chain, determined by the orientation of the sugar molecules.

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Phosphodiester bond

The chemical bond that connects nucleotides in a nucleic acid chain.

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Complementary base pairing

The specific pairing of nitrogenous bases in DNA; adenine with thymine, and guanine with cytosine.

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Antiparallel strands

Two DNA strands running in opposite directions.

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Primary Structure (DNA)

The sequence of nucleotides along a DNA strand.

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Secondary Structure (DNA)

The double helix structure formed by the hydrogen bonding of complementary bases.

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Tertiary Structure (DNA)

The complex 3D structure of DNA, reflecting its packing and interactions with proteins.

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DNA Double Helix Structure

DNA is composed of two anti-parallel strands of nucleotides, forming a right-handed helical structure with a major and minor groove.

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Phosphodiester Bonds in DNA

The sugar-phosphate backbone of DNA is held together by phosphodiester bonds, linking the 5' phosphate of one nucleotide to the 3' hydroxyl of the next.

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What causes the DNA helix to twist?

The phosphodiester bonds in the DNA backbone create torsional force that twist the double-stranded molecule into a helix.

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What is a Nucleosome?

A nucleosome is a basic unit of DNA packaging in eukaryotes, consisting of 160-200 base pairs of DNA wrapped around eight histone proteins.

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How are Nucleosomes linked together?

Nucleosomes are linked together by the linker histone protein H1, forming a solenoid structure.

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What is the difference between prokaryotic and eukaryotic DNA?

Prokaryotic DNA has a simpler structure with DNA folded into loops attached to proteins, while eukaryotic DNA has a more complex structure, including nucleosomes and higher order packaging.

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How long is a bacterial chromosome compared to the cell?

The bacterial chromosome in E. coli is about 1000 times longer than the bacterium itself.

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How long is the smallest human chromosome compared to the nucleus?

The smallest human chromosome is 14,000 times the length of the nucleus.

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What is chromatin?

Chromatin is the complex of DNA and proteins (like histones) that makes up chromosomes in eukaryotic cells.

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What does the 30 nm fiber look like?

The 30 nm fiber is a tightly packed structure of DNA organized into a solenoid-like coil.

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How does chromosome structure change during the cell cycle?

Chromatin condenses during M-phase (mitosis) and decondenses during interphase.

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What are the two types of chromatin?

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and transcriptionally inactive.

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What is the function of genomic DNA?

Genomic DNA carries the genetic instructions for building proteins and regulating gene expression.

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What is the function of mitochondrial DNA?

Mitochondrial DNA encodes for enzymes involved in oxidative phosphorylation, rRNA, and tRNA.

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What is the function of chloroplast DNA?

Chloroplast DNA encodes for redox proteins involved in photosynthesis.

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What is plasmid DNA?

Plasmid DNA is separate circular DNA found in some bacteria that can carry genes for things like drug resistance.

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Cyclic Nucleotide Monophosphates

These are nucleotides that act as cell signaling molecules. They play a crucial role in communication within cells.

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Coenzymes

These are non-protein molecules essential for the functioning of enzymes. They assist in metabolism by participating in biochemical reactions.

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Nucleotide Triphosphates

These high-energy nucleotides are like batteries for cells, storing and carrying energy. They can be converted into diphosphates to release energy.

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Energy Storage & Transport

Nucleotide triphosphates, like ATP, are the primary energy carriers in living organisms. They provide energy for cellular processes by releasing it during their conversion to ADP.

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Cofactors for Phosphorylation

Nucleotide triphosphates act as cofactors for enzymes that catalyze phosphorylation reactions, adding phosphate groups to molecules.

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Study Notes

Molecular Genetics (BHS016-1)

  • Course is taught by Dr Taiwo Shittu
  • Course code is BHS016-1

Nucleic Acids (BHS016-1 Topic 1)

  • Learning outcomes include:
    • Recall the chemical structures and key elements of nucleotides
    • Explain the formation of nucleic acids from individual nucleotides
    • Describe the 3D structure of DNA
    • Understand various functions of nucleic acids and nucleotides

What is Genetics?

  • Genetics is the study of heredity.
  • Heredity is controlled by genes.
  • Genes are units of biological information.
  • Genes are units of inheritance.

Why is Genetics Important?

  • Areas of study where genetics is important:
    • Biomedical science (e.g., heart damage from cancer drugs linked to faulty genes)
    • Biological science (e.g., extracting oldest genetic information from rhino tooth)
    • Forensic Science (e.g., genetic evidence used to solve crimes)

Basic Structure of the DNA Molecule

  • Details on the basic structure of DNA molecules will be discussed later.

How to Identify Genetic Material?

  • Unknown before the 1950s.
  • Key characteristics for genetic material:
    • Contains complex information
    • Replicates faithfully
    • Encodes the phenotype
  • Phenotype: Definition of observable characteristics.

How Do We Know It Is DNA?

  • History of key discoveries around DNA starting from 1869
  • Definition of chromatin
  • Importance of the tetranucleotide theory and its role in misdirection
  • Avery et al's work in 1944

Timeline of DNA as Genetic Code

  • Timeline of key DNA discoveries during the various years

How Do We Know It is DNA? (Experiments)

  • Avery et al studied 2 types of pneumonia bacteria
    • One (S) caused disease in mice, The other (R) did not.
    • Heated S bacteria loss its disease causing ability
    • Mixing heated S bacteria with R bacteria transformed the R bacteria into disease-causing bacteria.
    • Experiment determined the transforming molecule
  • Diagram of the experiment

1944 - Avery, MacLeod and McCarty

  • Experiment: Determined the chemical nature of the transforming substance
  • Methods, results, and conclusions of the experiment

How Can DNA Carry Information?

  • Kossel’s work in late 1800s
  • DNA contains four nitrogenous bases.
  • Definition of purine and pyrimidine
  • Levene demonstrated DNA was a polymer of nucleotides
  • Definition of a nucleotide

How Can DNA Carry Information?

  • Structure of a nucleotide
  • Chargaff's demonstration in 1948 of the fixed ratios of nucleotides
    • Fixed ratios of A/T and C/G for all DNA analyzed
  • Watson and Crick's discovery in 1953 of the DNA structure as a double helix
    • DNA is a double helix molecule made of two anti-parallel strands.
    • Pairing of A-T and C-G

Primary Structure of DNA

  • How nucleotides bonded together to form polymers via phosphodiester bonds
  • Definition of covalent
  • Definition of 5' and 3'

Phosphodiester Bond Formation

  • Diagram of phosphodiester bond

Phosphodiester Bonds = Backbone

  • Phosphodiester bonding produces a polymer with a sugar-phosphate backbone.

Secondary Structure of DNA

  • Chargaff’s rules related to base pairing
  • Bases pair via hydrogen bonding
  • Adenine to thymine by 2 hydrogen bonds
  • Guanine to cytosine by 3 hydrogen bonds
  • Definition of hydrogen bond

Base Pairing = Interior

  • Linear polynucleotide strands pair to form a double-stranded molecule
  • Pairing A-T or C-G called complementary base pairing
  • Complementary strands are antiparallel

Summary of Basic DNA Structure

  • DNA consists of 2 polynucleotide strands
  • Sugar-phosphate backbone on outside of molecule
  • Nitrogenous bases on the inside
  • Hydrogen bonds join bases of 2 strands
  • Adenine pairs with thymine, Guanine with cytosine
  • 2 polynucleotide strands are complementary and antiparallel

How Can DNA Carry Information?

  • Genetic material must contain complex information
  • Extremely long sequences "spelling" coded instructions
  • Genetic material must replicate faithfully, via complementary base pairing
  • Genetic material must encode the phenotype

Tertiary Structure of DNA

DNA Structure

  • Definitions of Primary, Secondary and Tertiary structures

DNA Is a Double Helix

  • Phosphodiester bonds cause torsional force twisting double-stranded DNA molecule

B-DNA Structure

  • Diagram of the structure of B-DNA

DNA Requires Further Packing

Prokaryote DNA Simple Structure

Bacterial DNA Folded In Twisted Loops (Diagram)

Eukaryotic DNA Shows Complex Packing (Diagram)

Double Helix Packed Into Nucleosomes

Nucleosomes Packed Into 30 nm Fibre

  • Diagram of the process

30 nm Fibre Packed Into Larger Coils

  • Diagram of the process

700 nm Coiled Coil Forms Chromosome

Eukaryotic DNA Shows Complex Packing (Detailed diagram and description)

DNA Packing Alters During Cell Cycle

  • Chromatin (DNA and proteins) structure changes during the cell cycle.
  • Tight packing during M-phase (condensation during prophase, and deccondensation during telophase)
  • Loose packing in interphase (euchromatin)
  • Tight packing in interphase (heterochromatin)
  • Definitions of euchromatin and heterochromatin

Functions of DNA and Nucleotides

  • DNA functions in eukaryotic and prokaryotic cells
  • Provides instructions for building proteins (genes)
  • Provides instructions for controlling gene expression (regulatory regions)
  • Contains non-coding DNA
  • Other types of DNA (mitochondrial DNA, chloroplast DNA, plasmid DNA)
  • Functions of nucleotides: act as cell signaling molecules (cyclic nucleotide monophosphates), coenzymes (coenzyme A, NAD), nucleotide triphosphates to provide energy

Functions Of Nucleotides

Summary – You should Now Know

To-Do List

  • Tasks related to reviewing DNA structure, writing definitions, diagrams of deoxynucleotides joining
  • Further notes and diagrams on histones, chromosome packing, chromatin (euchromatin and heterochromatin)
  • Table summarizing the functions of DNA and nucleotides

Before Next Week's Lecture

  • Reading about chromosome structure from textbooks (e.g. Pierce Genetics 6th ed. Chapter 2 and 11)

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