Molecular Text 4.2

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  1. ·         In 1999, it became possible for the first time to see exactly what? Today, the genetic info in all human chromosomes is available.
    o   The __ generated raw nucleotide sequence at a rate of 1000 nucleotides per second around the clock 
    how gene are arranged along an entire vertebrate chromosome

    Human Genome Project
  2. ·         Striking features of the human genome
    o   Little of it codes for __
    §  Most of the remaining DNA is made up of __ that have gradually __—they are __ 
    • proteins
    • short, mobile pieces of DNA
    • inserted themselves in the chromosome over evolutionary time
    • transposable elements
  3. • Striking features of the human genome 
    the __
    §  a typical gene carries in it linear sequence of nucleotides the information for the __
    ·         only about 1300 nucleotide pairs are required to __
    o   most of the remaining DNA in a gene consists of __ that __
    §  coding sequence: __
    §  intervening (noncoding) sequence: __
    • large average gene size of 27,000 nucleotide pairs
    • linear sequence of the amino acids of a protein
    • encode a protein of average size
    • long stretches of noncoding DNA
    • interrupt the relatively short segments of DNA that code for protein
    • exons
    • introns
  4. ·         Striking features of the human genome
    o   __:  responsible for ensuring that the gene is __  at the proper time and only in the proper type of cell
    §  in humans, the __ for a typical gene are __ over tens of thousands of nucleotide pairs, which are more compresed in organisms with concise genomes
    o   critical information needed to produce a human seem to be in an __
    • regulatory DNA sequence
    • turned on or off
    • regulatory sequences
    • spread out
    • alarming state of disarray
  5. ·         much of the __is probably unimportant
    o   the __ of the genome are typically found in __ floating in a sea of DNA whose exact nucleotide sequence is of little consequence
    §  this arrangement makes it difficult to __. It’s also hard to determine __ and __
    • sequence 
    • coding regions
    • short segments
    • identify all the exons in a stretch of DNA sequence
    • where a gene begins and ends and how many exons it spans
  6. o   one approach of __ is based on the observation that sequences that have a function are what, whereas those without a function are what?
    §  strategy: what?
    §  regions that are closely similar between organism are __; and, they include both __ and __
    • gene identification
    • relatively conserved during evolution
    • free to mutate randomly
    • to compare the human sequence with that of the corresponding regions of a related genome, such as that of the mouse
    • conserved regions
    • functionally important exons and regulatory DNA sequences
  7. §  nonconserved regions represent DNA whose __
    §  the power of this method can be increased by doing what? With this, comparative DNA sequencing studie have highlighted the most interesting regions in these genomes
    increased by comparing our genome with the genome of additional animals whose genomes have been completely sequenced
  8. ·         5% of human genome consists of “__”
    o   Only about 1/3 of these does what? 
    §  Some of the conserved noncoding sequences correspond to __ that are involved in __, while others produce __ that are not __ 
    ·         The function of a majority of these sequence remains unknown 
    • multi-species conserved sequences
    • sequences code for proteins
    • clusters of protein-binding sites
    • gene regulation
    • RNA molecules
    • translated into protein
  9. o   Large blocks of our genome contain these gene in the same order, a feature called __. As a result, large blocks of our chromosomes can be recognized in other species
    conserved synteny
  10. ·         To form a functional chromosome, a DNA molecule must be able to do more than simply __: it must be able to __, and the __ must be __and reliably __
    o   This process occurs through an ordered serie of stages, known as the __, which provides for a __ between the __ and __
    carry genes


    replicated copies


    partitioned into daughter cells at each cell division

    cell cycle

    temporal separation

    duplication of chromosomes and their segregation into two daughter cells
  11. ·         During interphase, __, and during mitosis they become __ and then are __ and __.
    o   The highly condensed chromosomes in a dividing cell are __, which are most easily visualized 
    • chromosomes are replicated
    • highly condensed
    • separated and distributed to the two daughter nuclei
    • mitotic chromosomes
  12. ·         A chromosome operates as a __: for a copy to be passed on to each daughter cell at division, each chromosome must be able to __, and the newly replicated copies must subsequently be __ and __
    o   These basic functions are controlled by three types of specialized __ in the DNA, each of which binds specific proteins that __
    • distinct structural unit
    • replicate
    • separated and partitioned correctly into two daughter cells
    • nucleotide sequences
    • guide the machinery that replicates and segregates chromosomes
  13. ·         One type of nucleotide sequence acts as a __, the location at which duplication of the DNA begins
    o   Eukaryotic chromosome contain many __ to ensure that the entire chromosome can be replicated rapidly
    • DNA replication origin
    • origins of replication
  14. ·         After replication, the two daughter chromosomes __ and, as the cell cycle proceeds, are __.
    o   The presence of a second specialized DNA sequence, called a __, allows one copy of each duplicated and condensed chromosome to be what?
    §  A protein complex called a __forms at the __and does what, allowing them to be __
    • remain attached to one another
    • condensed further to produce mitotic chromosomes
    • centromere
    • pulled into each daughter cell when a cell divides
    • kinetochore 
    • centromere 
    • attaches the duplicated chromosomes to the mitotic spindle
    • pulled apart
  15. ·         A third specialized DNA sequence forms __, the ends of a chromosome, which contain __ that enable the ends of the chromosomes to be efficiently replicated

    • telomeres
    • repeated nucleotide sequence
  16. o   Telomeres also perform another function: what is it?  
    the repeated telomere DNA sequences, together with the regions adjoining them, form structure that protect the end of the chromosome from being mistaken by the cell for a broken DNA molecule in need of repair
  17. ·         In yeast cells, the three types of sequences required to propagate a chromosome are __and use only a __
    o   In more complex organisms, the __ are longer
    • short 
    • fraction of the information-carrying capacity of a chromosome
    • telomere sequences
  18. ·         All eukaryotic organisms have special ways of __. __is performed by proteins that successively __ and __ the DNA into higher and higher levels of organization
    o   Although much less condensed than __, the DNA of __ is still tightly packed, with an overall compaction ratio of approximately 500-fold
    • packaging DNA into chromosomes
    • Compression 
    • coil and fold
    • mitotic chromosomes
    • human interphase chromosomes
  19. ·         __ is dynamic; and each chromosome condenses to an unusually degree in the__
    o   Specific regions of __ decondense as the cells __—and then __when the processes are completed
    §  The packaging of chromosomes is therefore accomplished in a way that allows __ to the DNA. 
    • Chromosome structure
    •  M phase of the cell cycle
    • interphase chromosomes
    • gain access to specific DNA sequences for gene expression, DNA repair, and replication
    • recondense 
    • rapid localized, on-demand access
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Molecular Text 4.2
Test One
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