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Sequencing the Genome quiz

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  • What is the first step in sequencing a genome?
    The first step is to chop the genomic DNA into random, overlapping fragments using restriction enzymes.
  • What are the overlapping DNA fragments generated during sequencing called?
    These overlapping fragments are called reads.
  • How does pyrosequencing detect the sequence of DNA?
    Pyrosequencing detects the sequence by measuring light signals released when nucleotides are incorporated into the DNA strand.
  • Why are overlapping reads important in genome sequencing?
    Overlapping reads are important because they allow sequencing software to assemble the full genome by matching overlapping regions.
  • What is a consensus sequence in genome assembly?
    A consensus sequence is the assembled sequence that represents the most common nucleotide at each position, accounting for individual differences.
  • How does traditional whole genome sequencing amplify DNA fragments?
    Traditional sequencing amplifies DNA fragments by inserting them into bacterial plasmids (vectors) and growing the bacteria.
  • What is a key difference between traditional and next generation whole genome sequencing?
    Traditional sequencing uses cells and bacteria for amplification, while next generation sequencing uses automated, cell-free reactions in small volumes.
  • Why do repetitive DNA sequences make genome assembly difficult?
    Repetitive sequences are hard to align and assemble because it's difficult to determine where they begin and end in the genome.
  • What are paired end reads and why are they useful?
    Paired end reads are sequences from both ends of a DNA fragment, useful for aligning repetitive regions and detecting genome changes.
  • How can paired end reads help identify genome rearrangements?
    Paired end reads can reveal insertions, deletions, inversions, and duplications by comparing the distance and orientation of known sequences.
  • What special nucleotides are used in Sanger sequencing to stop DNA replication?
    Sanger sequencing uses dideoxynucleotides (ddNTPs), which terminate DNA strand elongation when incorporated.
  • How does Sanger sequencing determine the DNA sequence?
    It generates DNA fragments of varying lengths that end at each nucleotide, then separates them by size to deduce the sequence.
  • What is the purpose of using a small amount of ddNTPs in Sanger sequencing?
    A small amount ensures that most replication proceeds normally, but occasional incorporation creates fragments ending at each nucleotide.
  • What is sequence assembly in genome sequencing?
    Sequence assembly is the process of using software to overlap and connect reads to reconstruct the full genome sequence.
  • Why is it necessary to have multiple reads covering each base pair in genome sequencing?
    Multiple reads ensure accuracy and help create a reliable consensus sequence by covering each base pair several times.