BEST IELTS General Reading Test 491

BEST IELTS General Reading Test 491

IELTS General Reading Test

A RESEARCH ABOUT TWINS

Studies of identical and fraternal twins have long been used to untangle the influences of genes and the environment on particular traits. Identical twins share all of their genes, while fraternal twins only share 50 percent. If a trait is more common among identical twins than fraternal twins, it suggests genetic factors are partly responsible.

Studies on the similarities and differences between twins are a powerful tool in the age-old Nature vs. Nurture debate. Most scientists believe his face-off between environment and genes has ultimately been settled. Modern twin studies have soundly proven that what makes a person unique is not a question of nature versus nurture. It’s a combination of the two: nature and nurture.

IELTS General Reading Test

“Twins studies are the only real way of doing natural experiments in humans,” says Tim Spector, a professor of genetic epidemiology at Kings College, London. “By studying twins, you can learn a great deal about what makes us tick, what makes us different, and particularly the roles of nature versus nature that you just can’t get any other way.” To understand modern twin studies, one must first understand the biology of twins. There are two different types of twins: identical, which scientists call monozygotic and fraternal, which scientists call dizygotic.

Monozygotic twins occur when a single egg is fertilized and then divides into two separate embryos. The resulting twins share nearly 100 percent of their genetic data. Dizygotic twins occur when two separate eggs in the mother’s ovaries are fertilized by two separate sperm, and share roughly 50 percent of their genetic data. “On average, dizygotic twins share the same amount of genetic info as I would share with my sisters,” says Louise Arseneault, who was a Principal Investigator of the Environmental Risk Study, which studies approximately 2,000 twins in the UK. “But I have a different age than my sisters. Dizygotic twins have the same age.

IELTS General Reading Test

“If the twins are two members of one family, so you can control for shared environment,” Arseneault says. Both twins are the same age and grew up experiencing many of the same things. Most twin studies use this assumption of shared environment to discern the differences brought on by genetics between sets of monozygotic and dizygotic twins.

By studying pairs of twins longitudinally or observing their lives through physical and psychological tests regularly across a period of many years or even entire lifetimes, scientists can use these similarities (mirrored genetics, for monozygotic twins, parents, household, economic situation, diet and schooling for both sets) and differences (uneven factors like bullying, abuse, and generally altered life course for both sets) to discover the reasons why two people with exactly the same or somewhat similar genes are alike or dissimilar. In this way, “twin studies allow us to estimate the importance of genetic factors versus environmental factors,” Arseneault says.

IELTS General Reading Test

Identical twins have non-identical fingerprints. Fingerprint patterns are unique and shaped by environmental factors in the womb, for example, access to nutrition and differences in umbilical cord length.

That doesn’t begin to take into account the benefit of comparisons between monozygotic twins, which have exactly the same genetics and dizygotic twins, which don’t. Since both sets will share the vast majority of environmental factors with their twins, the genetic variance is isolated. If the similarity between monozygotic twins is greater than that of dizygotic twins, that difference can be accounted for by genetics. If, for instance, a set of monozygotic twins both have similar vocabulary traits and a set of dizygotic twins with exactly the same environmental factors (for example, reading at home) have differing vocabulary tendencies, researchers might assume vocabulary is influenced not just by environment, but by genetics, too.

IELTS General Reading Test

Researchers also use discordant twin studies to examine the effects of environmental factors. For instance, if two monozygotic twins with the same genetics, home life and diet end up with drastically different life outcomes (say, one is a successful lawyer and the other in prison, or suffering from mental illness) researchers expect different environmental factors to have played a role in their divergent life courses. The twin study remains a common model in biology for removing confounding variables or outside factors that affect a study’s outcome.

That makes twin studies powerful in any of several ways: on their own, with a large sample size in order to prove new hypotheses about how our genetic differences trump environmental factors; used in conjunction with larger-scale, non-twin longitudinal studies to test hypotheses further, without confounding variables; or even in just a single set of twins that are identical but undergo a drastic environmental divergence. Two very different twin studies can show the blend of classical and pioneering science that’s currently being applied to twin studies as we continue to use them as a powerful learning tool.

IELTS General Reading Test

In twin study, researchers comb through dizygotic and monozygotic pairs, hunting for answers, but knowing above all that there is no silver bullet. Even in the perfect human study, the answers, as they always do in science, remain complex.

Do the following statements agree with the information given in the text above?

In boxes 27-34 on your answer sheet, write

TRUE – if the statement agrees with the information

FALSE – if the statement contradicts the information

NOT GIVEN – if there is no information on this

27. Modern behavioral geneticists believe that what makes a person unique is a combination of nature and nurture.

28. Discordant twin studies are used to examine the effects of hereditary factors.

29. If the similarity between monozygotic twins is greater than that of dizygotic twins, that difference can be accounted for by genetics.

IELTS General Reading Test

30. Two very different twin studies cannot be used a powerful learning tool in the field of science.

31. When a scientist looks at twins, she sees a natural study design.

32. Twins studies include longitudinally observing their lives through physical and psychological tests regularly across a period of many years.

33. The twin study remains a common model in biology for removing confounding variables or outside factors that affect a study’s outcome.

34. Twin studies also try to quantify the effect of a person’s shared environment and unique environment on a trait.

Write the appropriate letters A-D.

Which of the following TWO statements support twin studies?

A. Researchers comb through dizygotic and monozygotic pairs.

B. Acornucopia of traits cannot be studied.

C. The only real way of doing natural experiments in humans.

D. Doesn’t shed light on human behavioral genetics.

IELTS General Reading Test

Write the appropriate letters A-D.

In which of the following TWO conditions can twin studies not help prove hypothesis regarding particular research?

A. General epidemiological researches

B. Large sample size researches

C. Researches in conjunction with larger-scale, non-twin longitudinal studies

D. Non twin researches

IELTS General Reading Test

Write the appropriate letters A-D.

Which of the following TWO statements describes dizygotic twins?

A. Don’t have the same age.

B. Share the same amount of genetic info as siblings.

C. Share nearly 100 percent of their genetic data.

D. Two separate eggs form two separate embryos.

IELTS General Reading Test

SEE MORE POSTS>>

BEST IELTS General Reading Test 491

Get Latest IELTS Books

IELTS General Reading Test

27. TRUE

28. FALSE

29. TRUE

30. FALSE

31. NOT GIVEN

32. TRUE

33. TRUE

34. NOT GIVEN

35. A/C

36. A/C

37. B/C

38. B/C

39. B/D

40. B/D

IELTS General Reading Test

0 0 votes
Article Rating
Subscribe
Notify of
guest

0 Comments
Oldest
Newest Most Voted
Inline Feedbacks
View all comments

Best Hot Selling Books | Get Discount upto 20%

X
error: Content is protected !!
0
Would love your thoughts, please comment.x
()
x