Manipulating genomes

• What does the term genome refer to?

  All genes possessed by an individual
• What percentage of the human genome is identical across all individuals?

  99.9 percent
• What causes variations between different individuals in the genome?

  The remaining 0.1 percent of the genome
• What are the two types of genes within the genome?

  Exons and introns
• What do exons code for?

  Proteins
• What percentage of the genome do exons comprise?

  About 2 percent
• Why were introns previously called junk DNA?

  They were thought to have no function
• What is the current understanding of introns' function?

  They may regulate gene expression
• What are satellite DNA sequences?

  Short repeated DNA sequences
• What are the two types of satellite DNA?

  Mini-satellite and microsatellites
• What is another name for mini-satellites?

  Variable number tandem repeats (VNTRs)
• How long are mini-satellite sequences?

  About 15 to 20 base pairs long
• How many times do mini-satellites repeat?

  50 to 100 times
• How long are microsatellite sequences?

  About 2 to 4 base pairs long
• What is the process called that amplifies DNA fragments?

  Polymerase chain reaction (PCR)
• How many times do microsatellites repeat?

  5 to 15 times
• Why is PCR important in DNA manipulation?

  It allows amplification of DNA fragments
• Why are satellite DNA sequences useful in DNA profiling?

  They appear in the same area on chromosomes
• In a forensic situation, why do we need to amplify DNA?

  To generate a strong enough DNA profile
• What happens to DNA when comparing two individuals in DNA profiling?

  They have different numbers of repeats
• What are the three main steps in PCR?

  1. Denaturation
  2. Annealing
  3. Synthesis (or amplification)
• At what temperature does denaturation occur in PCR?

  95 degrees Celsius
• What is the principle of DNA profiling?

  Different people generate different DNA patterns
• What happens to molecules during denaturation?

  They gain kinetic energy and break hydrogen bonds
• What is the temperature for annealing in PCR?

  55 degrees Celsius
• What do identical twins share in terms of DNA profiling?

  Identical satellite patterns
• What role do primers play in PCR?

  They bind to the start of the gene to amplify
• How does DNA profiling help in forensics?

  It identifies individuals and familial relationships
• What is the temperature for the synthesis stage in PCR?

  72 degrees Celsius
• What is the function of TAC polymerase in PCR?

  It synthesizes new DNA strands at high temperatures
• What is the first step in the DNA profiling process at a crime scene?

  Extracting DNA from the evidence
• Why can't human DNA polymerase be used in PCR?

  It denatures at 72 degrees Celsius
• What is PCR in the context of DNA profiling?

  Polymerase chain reaction for DNA replication
• What happens to the DNA strands after synthesis in PCR?

  They undergo the same PCR cycle repeatedly
• What is the purpose of restriction endonucleases in DNA profiling?

  To cut DNA at specific sequences
• What do restriction sites refer to?

  Specific DNA sequences recognized by enzymes
• Describe the overall process of PCR.

  1. DNA is placed in a thermal cycler.
  2. Temperature is raised to 95°C for denaturation.
  3. Temperature is lowered to 55°C for annealing of primers.
  4. Temperature is raised to 72°C for synthesis using TAC polymerase.
  5. The cycle repeats to amplify DNA.
• What happens to introns during DNA profiling?

  They are cut at restriction sites
• What mistake was mentioned regarding the primers in PCR?

  Primers should bind at different points
• What is gel electrophoresis used for in DNA profiling?

  To separate DNA fragments by size