SAT Reading - Khan Diagnostic Quiz level 3 - reading 5

Questions 1-11 are based on the following

The Human Genome Project was an international scientific research project with the primary goal of mapping all of the genes that make up human DNA. Funded by the U.S. government, it began in 1990 and was successfully completed in 2003. Passage 1 is from the National Human Genome Research Institute website. Passage 2 is from Evolution and Medicine. ©2011 by BSCS.

Passage 1

The Human Genome Project has revealed that there are

probably about 20,500 human genes. The completed human

sequence can now identify their locations. This ultimate
Line product of the Human Genome Project has given the world a
5 resource of detailed information about the structure,

organization and function of the complete set of human

genes. This information can be thought of as the basic set of

inheritable "instructions" for the development and function

of a human being.
10 The International Human Genome Sequencing

Consortium published the first draft of the human genome in

the journal Nature in February 2001 with the sequence of the

entire genome's three billion base pairs some 90 percent

complete. A startling finding of this first draft was that the
15 number of human genes appeared to be significantly fewer

than previous estimates, which ranged from 50,000 genes to

as many as 140,000. The full sequence was completed and

published in April 2003.
Upon publication of the majority of the genome in
20 February 2001, Francis Collins, the director of the National

Human Genome Research Institute, noted that the genome

could be thought of in terms of a book with multiple uses:

"It's a history book - a narrative of the journey of our species

through time. It's a shop manual, with an incredibly detailed
25 blueprint for building every human cell. And it's a

transformative textbook of medicine, with insights that will

give healthcare providers immense new powers to treat,

prevent and cure disease."

Passage 2

Humans vary across the world. Every independently
30 conceived individual is genetically unique. This seems

paradoxical in light of the fact that all humans have a high

degree of genetic similarity. It is often reported that two

humans are 99.9 percent similar in their DNA. However, the

human genome is immense, providing multiple opportunities
35 for genetic variation to arise; the 0.1 percent by which we

differ amounts to 3.3 million nucleotides. Findings from the

International HapMap Project confirm previous studies and

show a relatively low amount of differentiation among

human groups defined by ethnicity and geography. There is
40 much more genetic variation within (about 90 percent) than

among (about 10 percent) human groups. This means that

the similarities among different groups of humans far outweigh

the differences.
As the ability to decipher the genotypes of individuals
45 improves and becomes more widely available, medical

practitioners will be better able to give patients specific

information about their health. Individual genetic profiles

provide useful information about disease susceptibility and

predispositions. Crews and Gerber (2008) suggest three
50 possible medical-clinical applications of individual genetic

profiling: improved screening, more-informed counseling,

and individualized drug formularies. Until more

individualized data are available, however, researchers

continue to try to determine whether disease susceptibility is
55 linked to specific genetic factors and, if so, whether the

genetic factors are distributed differentially among

geographic groups. Patterns of variation among humans have

been shaped by migration, genetic drift, mutation, and

natural selection. These evolutionary mechanisms lead to a
60 correlation between geographic distribution that may be

medically relevant.

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Question 1 As used in line 3, “ultimate” most nearly