Evolution and DNA Structure
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Questions and Answers

What is the term used for the complete set of observable traits that an organism displays?

  • Genotype
  • Phenotype (correct)
  • Genome
  • Heritage

How are inherited traits passed from one generation to the next?

  • By natural selection
  • Through DNA (correct)
  • Via RNA molecules
  • Through environmental changes

Which base pairs with adenine in the structure of DNA?

  • Guanine
  • Uracil
  • Cytosine
  • Thymine (correct)

What is the structure of DNA best described as?

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

What happens to DNA before a cell divides?

<p>It is copied (B)</p> Signup and view all the answers

Which of the following describes a mutation?

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

What is the role of DNA in an organism?

<p>To encode genetic information (D)</p> Signup and view all the answers

What component of DNA forms the backbone of its structure?

<p>Deoxyribose and phosphate groups (D)</p> Signup and view all the answers

What defines an auxotroph?

<p>An organism that cannot synthesize certain nutrients and requires them from the environment. (A)</p> Signup and view all the answers

What is a defining characteristic of resistant mutants?

<p>They can survive exposure to inhibitory molecules. (D)</p> Signup and view all the answers

How do regulatory mutations affect gene expression?

<p>They disrupt or create binding sites for transcription factors. (A)</p> Signup and view all the answers

Constitutive mutants are characterized by what feature?

<p>They exhibit no control over the expression of certain genes. (D)</p> Signup and view all the answers

What can be a consequence of a mutation during DNA replication?

<p>Loss of antibiotic sensitivity. (B)</p> Signup and view all the answers

What accurately describes the role of mutagens in bacterial DNA?

<p>They can induce mutations resulting in altered traits. (A)</p> Signup and view all the answers

Which statement is true about constitutive mutants?

<p>They continuously produce genes usually regulated by a repressor. (A)</p> Signup and view all the answers

What can mutations during DNA replication lead to?

<p>Generation of auxotrophic strains. (A)</p> Signup and view all the answers

What is a substitution mutation primarily defined as?

<p>A mutation that changes one nucleotide for another. (D)</p> Signup and view all the answers

What potential effect can a deletion mutation have on protein coding?

<p>It can cause a misinterpretation of the DNA sequence. (A)</p> Signup and view all the answers

Which of the following is an example of a frameshift mutation?

<p>Inserting an extra base pair into a sequence. (B)</p> Signup and view all the answers

What type of mutation results in no change to the protein produced?

<p>Substitution mutation. (B)</p> Signup and view all the answers

What could be a serious consequence of a frameshift mutation?

<p>It can lead to an incomplete protein. (B)</p> Signup and view all the answers

How do mutations contribute to evolution?

<p>They introduce genetic variation that can be acted upon by natural selection. (C)</p> Signup and view all the answers

Which condition is associated with a substitution mutation in the beta-hemoglobin gene?

<p>Sickle cell anemia. (B)</p> Signup and view all the answers

What characterizes a silent mutation?

<p>It has no effect on the resulting protein. (A)</p> Signup and view all the answers

What is horizontal gene transfer primarily responsible for in bacteria?

<p>Rapid adaptation and gene acquisition (A)</p> Signup and view all the answers

Which of the following is NOT a mechanism of horizontal gene transfer in bacteria?

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

What often happens to genes acquired through horizontal gene transfer if they provide no selective advantage?

<p>They are usually lost by deletion (D)</p> Signup and view all the answers

Transformation involves the incorporation of DNA from which source?

<p>A dead, degraded bacterium (B)</p> Signup and view all the answers

Which mechanism of horizontal gene transfer is most common among bacteria?

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

What is the effect of pathogenicity islands on bacterial genomes?

<p>They are large, unstable regions that can be transferred (C)</p> Signup and view all the answers

What is the result of homologous recombination during transformation?

<p>Replacement of similar DNA regions (B)</p> Signup and view all the answers

How much of the genome of Escherichia coli is estimated to have originated from horizontal gene transfer?

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

What is the primary effect of alkylating agents on DNA?

<p>They lead to point mutations through base mispairing. (B)</p> Signup and view all the answers

Which of the following represents a source of biological mutagens?

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

Antibiotics designed to disrupt the bacterial cell wall specifically target which process?

<p>Cellular membrane integrity (A)</p> Signup and view all the answers

What do extrachromosomal genetic elements such as plasmids often determine?

<p>Virulence factor production (A), Resistance to antimicrobial agents (D)</p> Signup and view all the answers

During which condition can bacteria increase their mutation rate significantly?

<p>When environmental stress is present (D)</p> Signup and view all the answers

How is genetic information in many viruses different from that in bacteria?

<p>Viruses may use RNA instead of DNA. (C)</p> Signup and view all the answers

What term describes the acquisition of new genes from other bacteria?

<p>Horizontal gene transfer (C)</p> Signup and view all the answers

What is a common outcome of mutations in bacteria?

<p>Most mutations are harmful. (D)</p> Signup and view all the answers

Which of the following bacteria are considered naturally competent and transformable?

<p><em>Neisseria meningitidis</em> (C)</p> Signup and view all the answers

What is the main role of autolysis in competent bacteria?

<p>To provide DNA for homologous recombination (D)</p> Signup and view all the answers

Which genera are involved in generalized transduction?

<p><em>Staphylococcus</em> and <em>Salmonella</em> (A)</p> Signup and view all the answers

What triggers the bacterium to manufacture bacteriophage components during transduction?

<p>The bacteriophage genome entering the bacterium (D)</p> Signup and view all the answers

How do competent bacteria acquire DNA from noncompetent cells?

<p>By killing noncompetent cells (B)</p> Signup and view all the answers

What is the defining characteristic of generalized transduction?

<p>Transfers any DNA fragment from one bacterium to another (C)</p> Signup and view all the answers

Which of the following is NOT a mechanism by which competent bacteria can transform?

<p>Degradation of their own DNA (B)</p> Signup and view all the answers

What occurs after a bacteriophage adsorbs to a susceptible bacterium?

<p>The bacteriophage injects its genome into the bacterium (D)</p> Signup and view all the answers

Flashcards

What is Evolution?

Evolution is a gradual process of change in species over many generations. It leads to diversity in all living things.

What drives evolution?

Changes in an organism's heritable traits are the driving force behind evolution.

What is a Genotype?

The complete set of genes in an organism's DNA.

What is a Phenotype?

The observable traits of an organism, determined by its genotype.

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What is DNA?

DNA is the molecule that carries genetic information, influencing an organism's development and function.

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What is the structure of DNA?

The two strands of DNA wind around each other, forming a structure like a twisted ladder.

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What is a Mutation?

A change in DNA sequence, the hereditary material of life.

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Mutation

A change in the DNA sequence that can alter an organism's traits, behavior, or physiology.

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Substitution Mutation

A type of mutation where one nucleotide base is replaced with another, potentially affecting the protein produced.

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Silent Mutation

A type of substitution mutation that doesn't alter the amino acid sequence despite the nucleotide change.

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Nonsense Mutation

A type of substitution mutation that changes a codon to a stop codon, leading to a prematurely terminated protein.

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Insertion Mutation

A mutation where extra DNA base pairs are inserted into the sequence.

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Deletion Mutation

A mutation where a section of DNA is removed.

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Frameshift Mutation

Mutations that disrupt the reading frame of a gene. Occur when insertions or deletions are not multiples of three.

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Mutagen

Any agent that can cause mutations in DNA. Examples include radiation, some chemicals, and viruses.

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Auxotrophic mutation

A mutation that affects a gene responsible for synthesizing an essential nutrient, preventing the organism from creating it on its own.

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Resistant mutants

Mutations that allow bacteria to survive in the presence of substances that would normally kill them, such as antibiotics.

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Regulatory mutation

A mutation that alters how genes turn on and off, affecting the expression of other genes.

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Constitutive mutant

Genes that are normally turned on and off are constantly switched on due to a mutation.

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DNA mutation

A change in DNA sequence, the hereditary material of life.

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Consequences of DNA mutations

Changes in DNA sequence can lead to alterations in the characteristics of an organism, such as its appearance or ability to resist antibiotics.

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Replication errors

The process where errors occur during DNA replication, causing alterations in the DNA sequence.

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Base Substitution

A type of mutation where one nucleotide base is replaced with another. This can change amino acid sequence, leading to altered protein function.

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Alkylating Agent

A type of mutagen that adds alkyl groups to nucleotide bases, often causing changes in DNA structure and function.

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Transposons

Mobile DNA sequences that can move and replicate within a genome, sometimes disrupting gene function when inserted into a new location.

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Horizontal Gene Transfer

Genetic material transfer between organisms that are not parent and offspring, often seen in bacteria and archaea.

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Transformation

A process where bacteria take up DNA fragments from their environment, often from dead bacteria, and incorporate them into their own genome.

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Transduction

A process where viruses transfer genetic material from one bacterium to another.

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Conjugation

A process where bacteria directly transfer genetic material through a physical connection, like a bridge.

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Pathogenicity Islands

Large DNA segments found in bacteria that encode for virulence factors, often transferred through horizontal gene transfer.

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Bacterial Evolution

The process where a bacterium gains new genes through horizontal gene transfer, allowing it to adapt to its environment.

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Bacterial Competence

The ability of a bacteria to pick up DNA from its surroundings and integrate it into its own genome.

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Unstable Regions of Bacterial Genome

Specific regions of DNA that are prone to deletion due to being unstable. Often carry genes acquired via horizontal gene transfer.

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Bacterial Transformation

A natural process where bacteria can directly absorb and incorporate exogenous DNA into their own genome. It allows for exchanging genetic material, leading to genetic variation and evolution.

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Competent Bacteria

Bacteria that are capable of taking up and integrating exogenous DNA from their environment.

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Killing Noncompetent Cells

A process where bacteria can kill other bacteria, releasing their DNA into the environment, which can then be taken up by other competent bacteria.

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Generalized Transduction

A type of transduction where any bacterial DNA can be transferred by a bacteriophage.

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Specialized Transduction

A type of transduction where only specific genes near the viral integration site are transferred by a bacteriophage.

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Bacteriophage

A bacteriophage that infects a bacterium and injects its genetic material, leading to the production of more bacteriophages.

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Bacteriophage Adsorption

The process where a bacteriophage attaches to a bacterium's surface and injects its genetic material into the bacterium.

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Study Notes

Evolution and Inheritance

  • Evolution is a gradual change in species over many generations, altering physical characteristics
  • Evolution results in biodiversity at all levels of biological organization
  • Evolution in organisms is through heritable changes
  • Heritable characteristics are inherited traits controlled by genes
  • Genotype is the complete set of genes in an organism's DNA
  • Phenotype is the observable traits of an organism, resulting from its genotype
  • Heritable characteristics are passed from one generation to the next through DNA

DNA Structure

  • DNA is a double helix molecule carrying genetic information for an organism's development and function
  • DNA is composed of two strands, each with a sugar-phosphate backbone
  • Four bases attach to the sugar: adenine (A), thymine (T), cytosine (C), and guanine (G)
  • Adenine pairs with thymine, and cytosine pairs with guanine.
  • DNA sequence encodes biological information (making proteins or RNA molecules)
  • DNA is copied before a cell divides, ensuring each new cell inherits the sequence.

Mutation

  • Mutation is a change in DNA, the hereditary material of an organism
  • Mutations affect an organism's physical characteristics, behaviors, and physiology
  • Mutations are essential for evolution as they are the source of genetic variation
  • Mutations can occur spontaneously or be caused by exposure to mutagenic agents
  • Mutations may be caused by replication errors, exposure to radiation, or chemical mutagens

Types of Mutations

  • Substitution: Exchanges one base for another (e.g., A to G)
    • May not change the resulting protein (silent mutation)
    • May change the amino acid in the protein
    • May create a premature stop codon, resulting in an incomplete protein
  • Insertion: Addition of extra base pairs in DNA
  • Deletion: Removal of a section of DNA

Frameshift Mutations

  • Insertions or deletions of base pairs can cause a frameshift
  • The reading frame of the genetic code is altered, causing the sequence to be read incorrectly, usually producing nonfunctional proteins

Causes of Bacterial DNA Mutations

  • Spontaneous mutations: Errors during DNA replication
  • Induced mutations: Exposure to mutagens (physical, chemical, or biological)

Physical Mutagens

  • UV radiation creates pyrimidine dimers (adjacent pyrimidine bases covalently linked)
  • Inhibiting DNA replication and translation

Chemical Mutagens

  • Base analogs: Structurally similar to normal nucleotides, causing mispairing during replication
  • Reactive oxygen species: Damage bases, such as guanine, causing mispairing
  • Deaminating agents: Remove amino groups from bases, altering base-pairing properties
  • Flat aromatic compounds: Intercalate between bases, causing distortions in DNA structure
  • Alkylating agents: Add alkyl groups to bases, changing their structure and pairing ability

Antibiotic Resistance

  • Mechanisms include DNA synthesis inhibitors, protein synthesis inhibitors, cell wall synthesis inhibitors, RNA synthesis inhibitors, mycolic acid synthesis inhibitors, and folic acid synthesis inhibitors

Genetic Information in Microbes

  • Bacteria and many viruses use DNA to store genetic information.
  • RNA plays a role in some viruses
  • Replication of genomes is essential for inheritance

Genome Organization

  • Bacterial chromosome is circular DNA
  • Additional genetic elements (plasmids) also present, not essential for survival but often harboring genes associated with antibiotic resistance, virulence traits, and other desirable characteristics
  • DNA replicates semiconservatively, one strand acting as a template for the new strand.

Horizontal Gene Transfer

  • Bacteria can acquire genes from other bacteria (through conjugation, transformation, or transduction)
  • Important for adaptation to new environments and acquiring traits like antibiotic resistance

Transposons

  • Small DNA segments that can "jump" to different locations in a genome
  • Often carry genes for traits that are advantageous to the organism

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Related Documents

MLS 531 Microbial Genetics (Evolution and Inheritance Mutation) PDF

Description

This quiz covers key concepts regarding evolution and the structure of DNA. It explores how heritable traits influence biological diversity and details the molecular characteristics of DNA. Test your understanding of fundamental genetic principles and their implications for inheritance.

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