CHROMOSOMES

• What are chromosomes?

  Structures that contain genetic material
• What are chromosomes made of?

  Complexes of DNA and proteins
• What does the genome comprise?

  All genetic material of an organism
• How is the genome structured in bacteria?

  Typically a single circular chromosome
• What does the genome refer to in eukaryotes?

  One complete set of nuclear chromosomes
• What additional genomes do eukaryotes possess?

  Mitochondrial and chloroplast genomes
• What is the main function of genetic material?

  To store information required to produce an organism
• How does DNA store information?

  Through its base sequence
• What are the necessary DNA sequences for cellular functions?

  Synthesis of RNA and proteins, segregation, replication, compaction
• What are the key functions of DNA sequences?

  • Synthesis of RNA and proteins
  • Proper segregation of chromosomes
  • Replication of chromosomes
  • Compaction of chromosomes
• What are viruses composed of?

  Nucleic acid surrounded by a protein capsid

  
• How do viruses replicate?

  By relying on their host cells
• What is the typical host range of viruses?

  Limited to specific types of cells
• What is a viral genome?

  The genetic material of the virus
• What types of genetic material can a viral genome be?

  DNA or RNA, single or double-stranded
• How does the size of viral genomes vary?

  From a few thousand to over a hundred thousand nucleotides
• Where is the bacterial chromosome located?

  In a region called the nucleoid
• What is unique about the nucleoid?

  It is not membrane-bounded
• What is the typical structure of bacterial chromosomal DNA?

  A circular molecule a few million nucleotides long

  
• How many copies of the bacterial chromosome can exist?

  One to four identical copies

  
• How many base pairs does Escherichia coli have?

  Approximately 4.6 million base pairs
• How many base pairs does Haemophilus influenzae have?

  Approximately 1.8 million base pairs
• What accounts for the majority of bacterial DNA?

  Structural gene sequences encoding proteins
• What are intergenic regions?

  Nontranscribed DNA between adjacent genes
• What is required for bacterial chromosomal DNA to fit within the cell?

  • Compacted about 1000-fold
  • Formation of loop domains
• How many loops does E. coli have in its chromosome?

  50-100 loops
• What is DNA supercoiling?

  A method to compact the bacterial chromosome

  
• What enzymes control supercoiling in bacteria?

  DNA gyrase and DNA topoisomerase I

  
• What does DNA gyrase do?

  Introduces negative supercoils using ATP

  
• What does DNA topoisomerase I do?

  Relaxes negative supercoils
• How many sets of chromosomes do eukaryotic species contain?

  One or more sets of chromosomes
• What is the structure of eukaryotic chromosomes?

  Several different linear chromosomes

  
• Where are eukaryotic chromosomes located?

  In the nucleus
• What are chromosomes?

  Structures that contain the genetic material
• What is the main function of the genetic material?

  To store information required to produce an organism
• What is a viral genome?

  The genetic material of a virus
• Why do viruses rely on their host cells for replication?

  Because they lack the machinery to replicate on their own
• What is the typical size range of viral genomes?

  From a few thousand to more than a hundred thousand nucleotides

  
• Where is the bacterial chromosome located?

  In the nucleoid region
• Why is the bacterial chromosome not membrane-bounded?

  So the DNA is in direct contact with the cytoplasm