Research Using Twins — IELTS Reading Answers

There may be genetic causes for the differences in how young the skin of identical twins looks.

“Any differences between them – one twin having younger looking skin, for example – must be due to environmental factors such as less time spent in the sun.”

The passage says any difference between identical twins, including younger-looking skin, must be due to environmental factors, ruling out genetic causes.

Twins are at greater risk of developing certain illnesses than non-twins.

“If identical twins are more similar to each other with respect to an ailment than fraternal twins are, then vulnerability to the disease must be rooted at least in part in heredity.”

The text only compares identical with fraternal twins to locate heredity's role; it never says twins as a group face greater illness risk than non-twins.

Bouchard advertised in newspapers for twins who had been separated at birth.

“Over two decades 137 sets of twins eventually visited Thomas Bouchard’s lab in what became known as the Minnesota Study of Twins Reared Apart.”

The passage records that 137 sets of twins eventually visited Bouchard's lab but says nothing about how they were recruited, so newspaper advertising is unsupported.

Epigenetic processes are different from both genetic and environmental processes.

“Epigenetic processes are chemical reactions tied to neither nature nor nurture but representing what researchers have called a ‘third component’.”

Being tied to neither nature nor nurture and called a third component makes epigenetics distinct from both genetic and environmental processes.

invented a term used to distinguish two factors affecting human characteristics

“when the English scientist Francis Galton first suggested the approach (and coined the phrase ‘nature and nurture’).”

Galton coined the phrase nature and nurture, the paired term separating two influences on human characteristics, so he is person A.

expressed the view that the study of epigenetics will increase our knowledge

“Having said that, Reed adds, the latest work in epigenetics promises to take our understanding even further.”

Reed says the latest work in epigenetics promises to take our understanding even further, the view that it will expand knowledge, person C.

developed a mathematical method of measuring genetic influences

“Bouchard and his colleagues used this mountain of data to identify how far twins were affected by their genetic makeup. The key to their approach was a statistical concept called heritability.”

Bouchard's team relied on a statistical concept called heritability, a mathematical measure of genetic influence, which is person B.

pioneered research into genetics using twins

“The idea of using twins to measure the influence of heredity dates back to 1875, when the English scientist Francis Galton first suggested the approach (and coined the phrase ‘nature and nurture’).”

Galton first suggested using twins to measure heredity in 1875, so he pioneered the approach, person A.

carried out research into twins who had lived apart

“with the arrival of studies into identical twins who had been separated at birth and reunited as adults. Over two decades 137 sets of twins eventually visited Thomas Bouchard’s lab in what became known as the Minnesota Study of Twins Reared Apart.”

Bouchard's Minnesota Study of Twins Reared Apart examined twins separated at birth and reunited as adults, matching research into twins who lived apart, B.

“Epigenetic processes are chemical reactions”

The gap needs the term for what epigenetic processes are; the passage defines them as chemical reactions tied to neither nature nor nurture, so option D.

“Other epigenetic processes appear to occur randomly, while others are normal, such as those that guide embryonic cells as they become heart, brain, or liver cells, for example.”

The gap needs an adverb describing how some epigenetic processes arise; the passage says others appear to occur randomly, so option B.

“One way the study of epigenetics is revolutionizing our understanding of biology is by revealing a mechanism by which the environment directly impacts on genes.”

The gap concerns how environment affects genes; the passage describes a mechanism by which the environment directly impacts on genes, option E.

“when a rat experiences stress during pregnancy, it can cause epigenetic changes in a fetus that lead to behavioral problems as the rodent grows up.”

The rat example shows maternal stress in pregnancy causing fetal epigenetic changes that later produce behavioural problems, option F.