Anatomy of Microbial and Eukaryotic Genomes
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Questions and Answers

What is the primary function of resistance plasmids?

  • Enhancing fertility in bacterial populations
  • Providing antibiotic resistance (correct)
  • Producing toxins to eliminate competitors
  • Facilitating DNA transfer between bacteria

Which plasmid type is responsible for the synthesis of toxins that kill other bacteria?

  • Transposon plasmids
  • Killer plasmids (correct)
  • Resistance plasmids
  • Fertility plasmids

Fertility plasmids primarily facilitate which of the following processes in bacteria?

  • Phage resistance
  • Synthesis of antibiotics
  • Conjugation and DNA transfer (correct)
  • Production of toxins

An example of a killer plasmid is?

<p>Col of <em>Escherichia coli</em> (A)</p> Signup and view all the answers

Which type of plasmid is NOT associated with antibiotic resistance?

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

Which type of organisms generally have a diploid genome?

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

What is the primary characteristic of prokaryotic genomes compared to eukaryotic genomes?

<p>Prokaryotic genomes have fewer nucleotide pairs. (A)</p> Signup and view all the answers

What percentage of the human genome is typically noncoding DNA?

<p>98.5% (C)</p> Signup and view all the answers

What is the role of promoters in the genome?

<p>They provide binding sites for transcription machinery. (C)</p> Signup and view all the answers

In contrast to eukaryotes, prokaryotes typically have how many copies of their genome?

<p>1 copy (A)</p> Signup and view all the answers

How do closely related organisms vary in their genomes despite similar functional gene numbers?

<p>They may differ greatly in DNA quantity. (A)</p> Signup and view all the answers

Which statement is true regarding noncoding regions in prokaryotic and eukaryotic genomes?

<p>Eukaryotes have a higher percentage of noncoding DNA than prokaryotes. (B)</p> Signup and view all the answers

What is the primary difference in the number of genes between human genomes and typical bacterial genomes?

<p>Humans have more genes than bacteria. (B)</p> Signup and view all the answers

What type of genome structure is exemplified by Borrelia burgdorferi B31?

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

What is a characteristic feature of prokaryotic genomes compared to lower eukaryotes?

<p>They are more compact. (D)</p> Signup and view all the answers

Which of the following best describes an operon?

<p>A group of genes expressed simultaneously. (D)</p> Signup and view all the answers

In a 50-kb segment of the E. coli K12 genome, what percentage of the segment is occupied by 43 genes?

<p>85.9% (D)</p> Signup and view all the answers

Which is a potential consequence of the compactness of prokaryotic genomes?

<p>Increased gene density. (C)</p> Signup and view all the answers

What unit is typically used to express the length of the human genome?

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

What distinguishes thrA, thrB, and thrC in the E. coli genome?

<p>They share an operon structure. (B)</p> Signup and view all the answers

What is a unique feature of plasmids compared to chromosomal DNA?

<p>They are circular and smaller. (C)</p> Signup and view all the answers

What role do silencers have in transcription regulation?

<p>They prevent transcription by providing binding sites for repressive proteins. (C)</p> Signup and view all the answers

What distinguishes prokaryotic genomes from eukaryotic genomes?

<p>Prokaryotic genomes possess a single circular DNA molecule. (C)</p> Signup and view all the answers

What is the approximate size of the E. coli K12 genome?

<p>4639 kb (C)</p> Signup and view all the answers

Which type of gene does NOT give rise to proteins?

<p>Transcribed non-coding regions (D)</p> Signup and view all the answers

What can plasmids provide to prokaryotes?

<p>Genetic traits like antibiotic resistance. (B)</p> Signup and view all the answers

How does the organization of prokaryotic genomes typically differ from that of eukaryotic genomes?

<p>Prokaryotic genomes lack complex regulatory elements. (A)</p> Signup and view all the answers

What is a common misconception about E. coli in relation to prokaryotes?

<p><em>E. coli</em> is seen as a typical prokaryote despite genomic diversity. (A)</p> Signup and view all the answers

Which statement about prokaryotic plasmids is accurate?

<p>Plasmids can impart additional capabilities like utilizing complex compounds. (A)</p> Signup and view all the answers

What type of enzymes are produced by the TOL plasmid of Pseudomonas putida?

<p>Degradative enzymes for unusual molecules (B)</p> Signup and view all the answers

Which bacterium is known for causing crown gall disease on dicotyledonous plants?

<p><em>Agrobacterium tumefaciens</em> (B)</p> Signup and view all the answers

How many circular DNA molecules does Vibrio cholerae possess?

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

What percentage of Vibrio cholerae's genes are located on the larger DNA molecule?

<p>71% (D)</p> Signup and view all the answers

How does the average length of a bacterial gene compare to that of a eukaryotic gene?

<p>Bacterial genes are shorter than eukaryotic genes, averaging about two-thirds the length. (A)</p> Signup and view all the answers

What is a characteristic feature of the smaller DNA molecule in Vibrio cholerae?

<p>Has integrons for capturing genes (D)</p> Signup and view all the answers

What is one distinguishing feature of prokaryotic genes compared to eukaryotic genes?

<p>Prokaryotic genes do not contain introns. (D)</p> Signup and view all the answers

What is the size of E. coli K12's chromosome?

<p>4.6 Mb (C)</p> Signup and view all the answers

What type of repetitive sequences are found infrequently in prokaryotic genomes?

<p>High-copy-number genome-wide repeat families. (C)</p> Signup and view all the answers

Which characteristic is typical of the genes located on the larger DNA molecule of Vibrio cholerae?

<p>Encode central cellular activities (B)</p> Signup and view all the answers

What is the characteristic of the insertion sequence found in bacteria?

<p>It is a short transposable element. (C)</p> Signup and view all the answers

What is considered the 'genome' in the context of E. coli K12's genetic organization?

<p>The chromosome only (B)</p> Signup and view all the answers

Which of the following statements about prokaryotic gene structure is false?

<p>Prokaryotic genes frequently include multiple introns. (C)</p> Signup and view all the answers

What type of genes are virtually absent in prokaryotes?

<p>Discontinuous genes. (C)</p> Signup and view all the answers

Which feature differentiates eukaryotic genomes from prokaryotic genomes?

<p>Eukaryotic genomes possess high-copy-number repeat families. (A)</p> Signup and view all the answers

In what genetic aspect do bacterial genes slightly differ from archaeal genes?

<p>Bacterial genes are shorter than archaeal genes on average. (C)</p> Signup and view all the answers

Flashcards

Prokaryotic genome size

Smaller than eukaryotic genomes.

Eukaryotic genome size

Larger than prokaryotic genomes, contains significantly more non-coding DNA.

Genome size measurement

Measured in nucleotide pairs of DNA per haploid genome.

Haploid genome

A single copy of an organism's genome.

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Diploid genome

Two copies of each chromosome (one maternal, one paternal) found in many sexually reproducing organisms.

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Non-coding DNA

DNA that does not code for proteins or other functional molecules in eukaryotes.

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Promoters

DNA sequences that signal the location of a gene and initiate transcription (DNA being made into RNA).

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Untranscribed regions

Non-coding genome regions that are not transcribed into RNA.

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Silencers

DNA sequences that bind proteins to repress gene transcription.

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Transcribed non-coding region

DNA regions that are transcribed but do not code for proteins; include rRNA and tRNA genes.

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Protein-coding region

DNA regions that code for proteins.

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Prokaryotic genome

Typically a single circular DNA molecule, but may also include plasmids.

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Plasmid

Small, circular or linear DNA molecules separate from the main chromosome in prokaryotes.

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Unipartite genome

A prokaryotic genome with a single chromosome.

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Eukaryotic genome

A genome with multiple linear chromosomes, often much larger than prokaryotic genomes.

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Prokaryotic Genome

The complete set of genetic material in a prokaryotic cell, often more compact than eukaryotic genomes.

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Operon

A group of genes that are clustered together and transcribed together, usually involved in a single biochemical pathway.

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Multipartite Genome

A genome that contains more than one chromosomal segment, consisting of linear and circular components.

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kb

Abbreviation for kilobase, a unit of DNA length equal to 1,000 base pairs.

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Compact Genome

A genome in which genes are arranged densely with less spacing between them and more genes.

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Gene Density

The number of genes per unit length of DNA.

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Plasmid

Small, circular DNA molecules found in some prokaryotic cells, separate from the main chromosome.

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Prokaryotic gene length

Generally shorter than eukaryotic genes, about two-thirds the length, even after intron removal in eukaryotes.

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Introns in prokaryotes

Rare or absent in prokaryotic genes, unlike eukaryotic genes, which often contain them.

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Repetitive sequences in prokaryotes

Generally less frequent than in eukaryotes, unlike eukaryotes, they have fewer repetitive genome-wide elements.

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Insertion sequence (IS)

Short transposable element found in bacteria, moving pieces of DNA.

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E. coli genome structure

Doesn't have introns; its genes are continuous and it has fewer repetitive sequences.

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Resistance plasmid function

Carries genes for antibiotic resistance, enabling bacteria to survive exposure to antibiotics.

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Fertility plasmid function

Enable transfer of genetic material between bacteria, often through conjugation.

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Killer plasmid function

Code for toxins that harm or kill other bacteria, giving a selective advantage.

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Plasmids

Small, circular DNA molecules separate from the main bacterial chromosome and often carry useful genes

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Colicin production in E. coli

Certain genes in bacteria like E. coli can produce proteins called colicins that can harm or kill other bacteria.

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Degradative enzymes in P. putida for toluene metabolism

Pseudomonas putida contains enzymes that break down toluene, a compound found in some environments.

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Virulence genes in A. tumefaciens

Some strains of Agrobacterium tumefaciens produce genes enabling them to cause disease in plants.

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Bacterial chromosome definition

The main chromosome in a prokaryotic cell is considered the genome. This is often a single circular DNA molecule.

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Genome in V. cholerae

Vibrio cholerae has two circular DNA molecules of different sizes (one much larger), together composing its genome, crucial for its pathogenicity.

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Plasmid influence on pathogenic genes

In some bacteria, plasmids may contain virulence genes, while also having essential cellular activities located elsewhere.

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Integron role in plasmids

Integron structures in some plasmids allow genes to be added or removed, enabling adaptability in different conditions.

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Study Notes

Anatomy of Microbial and Eukaryotic Genomes

  • Biologists recognize two types of organisms: eukaryotes and prokaryotes.
  • Eukaryotes have membrane-bound compartments (nucleus, mitochondria, chloroplasts in plant cells).
  • Prokaryotes lack extensive internal compartments.
  • Prokaryotes are divided into bacteria and archaea.
  • Bacteria include common prokaryotes like E. coli, gram-positives, cyanobacteria.
  • Archaea are less well-studied, often found in extreme environments (hot springs, brine pools).
  • Prokaryotic genomes are smaller than eukaryotic genomes.
  • Genome size is measured in nucleotide pairs per haploid genome.
  • Diploid organisms (e.g., humans) have two copies of the genome.
  • Related organisms often have similar numbers of functionally distinct genes but diverse DNA quantities.

Genome Comparison

  • Eukaryotes have vastly more DNA than prokaryotes, much of it non-coding.
  • Human genomes contain 1000 times more nucleotide pairs than bacterial genomes.
  • Human genomes have 20 times more genes but 98.5% non-coding DNA versus bacteria's 11%.
  • Genome regions can be: untranscribed (non-coding), transcribed non-coding (rRNA and tRNA genes), and protein-coding.

Prokaryotic Genomes

  • Prokaryotic genomes are different from eukaryotic ones.
  • E. coli K12 genome is 4,639kb compared to yeast which is larger.
  • E. coli has significantly fewer genes (4,405).
  • Prokaryotes can have single circular DNA molecules or additional smaller circular/linear DNA molecules, called plasmids.
  • Plasmids carry genes like antibiotic resistance.
  • Plasmids are considered dispensable; prokaryotes can function without them.
  • Prokaryotic genomes are compact.
  • Genes can be close together with little space.

Prokaryotic Genomes (continued)

  • A 50kb segment of E.coli K12 genome has more genes (43) with less space and many genes are very close together.
  • Operons are groups of genes in a pathway expressed collectively.
  • Prokaryotes have fewer repetitive sequences.
  • Some prokaryotic genomes contain insertion sequences (IS elements) that are short transposable elements

Complications in Studying E. coli

  • Recent studies indicate that prokaryotic genomes are more complex than previously thought.
  • A lot of linear chromosomes are found in bacteria and archaea, beyond the assumed circular structure.
  • Plasmids are independent parts of bacterial genomes (able to transfer among cells of different species).

More on Genomes

  • Archaea have DNA packaging proteins similar to eukaryote histones.

Comparing Prokaryotic and Eukaryotic Genomes

  • Prokaryotic genes are generally shorter, including approximately two-thirds the length of eukaryotic genes.
  • Prokaryotes lack introns.
  • Eukaryotic gene locations and structures differ significantly.

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Description

Explore the fundamental differences between microbial and eukaryotic genomes in this quiz. Understand the structure, size, and classification of DNA in prokaryotes and eukaryotes, including their unique features like non-coding regions and compartmentalization. Test your knowledge on genome comparisons and the diversity of life forms.

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