Youshould spend about 20 minutes on Question 14-26 which are based on ReadingPassage below.
A
Thescientific study of twins goes back to the late 19th century, when FrancisGalton, an early geneticist, realized that they came in two varieties:identical twins born from one egg and non-identical twins that had come fromtwo. That insight turned out to be key, although it was not until 1924 that itwas used to formulate what is known as the twin rule of pathology, and twinstudies really got going.
B
The twinrule of pathology states that any heritable disease will be more concordant(that is, more likely to be jointly present or absent) in identical twins thanin non-identical twins—and. in turn, will be moreconcordant in non-identical twins than in non-siblings. Early work, forexample, showed that the statistical correlation of skin-mole counts betweenidentical twins was 0.4, while non-identical twins had a correlation of only0.2. (A score of 1.0 implies perfect correlation, while a score of zero impliesno correlation.) This result suggests that moles are heritable, but it alsoimplies that there is an environmental component to the development of moles,otherwise the correlation in identical twins would be close to 1.0.
C
Twinresearch has shown that whether or not someone takes up smoking is determinedmainly by environmental factors, but once he does so, how much lie smokes islargely down to his genes And while a person's religion is clearly a culturalattribute, there is a strong genetic component to religious fundamentalism.Twin studies arc also unraveling the heritability of various aspects ofhuman personality. Traits from neuroticism and anxiety to thrill-and novelty-seeking all have large genetic components. Parenting matters, butit does not determine personality in the way that some had thought. D
Moreimportantly, perhaps, twin studies arc helping the understanding of diseasessuch as cancer, asthma, osteoporosis, arthritis and immune disorders. And twinscan be used, within ethical limits, for medical experiments. A study thatadministered vitamin C to one twin and a placebo to the other found that it hadno effect on the common cold. The lesson from all today's twin studies is thatmost human traits are at least partially influenced by genes. However, for themost part, the age-old dichotomy between nature and nurture is not very useful.Many genetic programs are open to input from the environment, and genes arc frequentlyswitched on or off by environmental signals. It is also possible that genesthemselves influence their environment. Some humans have an innate preferencefor participation in sports. Others are drawn to novelty. Might people also bedrawn to certain kinds of friends and types of experience? In this way, aperson's genes might shape the environment they act in as much as theenvironment shapes the actions of the genes.
E
In thepast, such research has been controversial. Josef Mengele, a Nazi doctor workingat the Auschwitz extermination camp during the Second World War, was fascinatedby twins. He sought them out among arrivals at the camp and preserved them fromthe gas-chambers for a series of brutal experiments. After the war, Cyril Burt,a British psychologist who worked on the heredity of intelligence, tainted twinresearch with results that appear, in retrospect, to have been rather too good.Some of his data on identical twins who had been reared apart were probablyfaked. In any case, the prevailing ideology in the social sciences after thewar was Marxist, and disliked suggestions that differences in human potentialmight have underlying genetic causes. Twin studies were thus viewed withsuspicion.
F
Theideological pendulum has swung back; however, as the human genome project andits aftermath have turned genes from abstract concepts to real pieces of DNA.The role of genes in sensitive areas such as intelligence is acknowledged byall but a few die-hards. The interesting questions now concern how nature andnurture interact to produce particular bits of biology, rather than which ofthe two is more important Twin studies, which are a good way to ask thesequestions, are back in fashion, and many twins are enthusiastic participants inthis research.
G
Researchat the Twinsburg festival began in a small way, with a single stand in 1979.Gradually, news spread, and more scientists began turning up. This year, half adozen groups of researchers were lodged in a specially pitched research tent.In one corner of this tent. Paul Breslin, who works at the Monell Institute inPhiladelphia, watched over several tables where twins sat sipping clear liquidsfrom cups and making notes. It was the team's third year at Twinsburg. DrBreslin and his colleagues want to find out how genes influence humanperception, particularly the senses of smell and taste and those (warmth, cold,pain, tingle, itch and so on) that result from stimulation of the skin.Perception is an example of something that is probably influenced by both genesand experience. Even before birth, people are exposed to flavours such aschocolate, garlic, mint and vanilla that pass intact into the bloodstream, andthus to the fetus. Though it is not yet clear whether such pre-natal exposureshapes taste-perception there is evidence that it shapes preferences for foodsencountered later in life.
H
However,there are clearly genetic influences at work, as well—for example in the ability to taste quinine. Some people experience this asintensely bitter, even when it is present at very low levels. Others, whosegenetic endowment is different, are less bothered by it. Twin studies make thisextremely clear. Within a pair of identical twins, cither both, or neither,will find quinine hard to swallow. Non-identical twins will agree lessfrequently.
I
On theother side of the tent Dennis Drayna, from the National Institute on Deafnessand Other Communication Disorders, in Maryland, was studying hearing. He wantsto know what happens to sounds after they reach the car. It is not clear, hesays, whether sound is processed into sensation mostly in the ear or in thebrain. Dr Drayna has already been involved in a twin study which revealed thatthe perception of musical pitch is highly heritable. At Twinsburg, he isplaying different words, or parts of words, into the left and right ears of histwinned volunteers. The composite of the two sounds that an individual reportshearing depends on how he processes this diverse information andthat, Dr Drayna believes, may well be influenced by genetics. J
Elsewherein the marquee, Peter Miraldi, of Kent State University in Ohio, was trying to findout whether genes affect an individual's motivation to communicate with others.A number of twin studies have shown that personality and sociability archeritable, so he thinks this is fertile ground. And next to Mr. Miraldi was ateam of dermatologists from Case Western Reserve University in Cleveland. Theyare looking at the development of skin diseases and male-pattern baldness. Thegoal of the latter piece of research is to find the genes responsible formaking men's hair fall out. K
Thebusiest part of the tent, however, was the queue for forensic-science researchinto fingerprints The origins of this study are shrouded in mystery For manymonths, the festival's organizers have been convinced that the Secret Service—the American government agency responsible for, among other things, thesafety of the president—is behind it. When The Economistcontacted the Secret Service for more information, we were referred to SteveNash, who is chairman of the International Association for Identification(LAI), and is also a detective in the scientific investigations section of theMarin County Sheriffs Office in California. The LAI, based in Minnesota, is anorganization of forensic scientists from around the world. Among other things,it publishes the Journal of Forensic Identification.
Questions14-18
Thereading Passage has paragraphs A-K
Whichparagraph contains the following information?
Writethe correct letter A-K, in boxes 14-18 on your answer sheet
NB Youmay use any letter more than once.
14.Mentioned research conducted in Ohio
15.Medical contribution to the researches for twins.
16.Research situation under life threatening conditions
17. Dataof similarities of identical twins
18.Reasons that make one study unconvincing
Questions19-20
Completethe following summary of the paragraphs of Reading Passage, using No More ThanTwo Words from the Reading Passage for each answer. Write your answers in boxes19-20 on your answer sheet.
Thefirst one that conducted research on twins is called 19 . He separated twinsinto two categories: non identical and identical twins. The twin research wasused in medical application in as early as the year of 20 .
Questions21-23
Choosethe correct letters in following options:
Writeyour answers in boxes 21-23 on your answer sheet.
Pleasechoose THREE research fields that had been carried out in Ohio, Maryland andTwinsburgh?
A Sense
B Cancer
C Beallergic to Vitamin D
D Moleheredity
E Sound
FBoldness of men
Questions24-26
Choosethe correct letters in following options:
Writeyour answers in boxes 24-26 on your answer sheet.
Pleasechoose THREE results that had been verified in this passage.
A Non identicaltwins come from different eggs.
BGenetic relation between identical twins is closer than non-identical ones.
CVitamin C has evident effect on a cold.
DGenetic influence to smoking is superior to environment's
E If apregnant woman cats too much sweet would lead to skin disease.
F Hairloss has been found to be connected with skin problem.
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