Номер 1, страница 1, часть 1 - гдз по английскому языку 9 класс учебник Демченко, Юхнель

Optional lesson. Same or different?

1. a. Look at the photo. What do they have in common?

b. Read the article. What factors lead to similarities and differences between twins1?

Identical twins: not so identical after all

How much of what makes you who you are is determined by your genes or your environment? Why might one person get cancer or heart disease and another not – is it their genetic profile, what they ate (or didn’t eat), how much (or how little) they exercised or other lifestyle factors? In other words, it’s the age-old nature-nurture debate, with nature referring to our genes and nurture meaning all the variables in our environment, from whether we worked night shifts, spent a lot of time sunbathing or rarely exercised. Hoping to understand the relationship between nature and nurture scientists have been studying identical twins for decades.

Despite the name, identical twins are rarely completely identical. Their skin tone, weight, height or personality, to name a few characteristics, may be different. How does this happen?

Every time a cell divides, your DNA2 must replicate, and that is a very complicated process. According to Rita Cantor PhD, Professor Emeritus of human genetics at the David Geffen School of Medicine at UCLA, “Cell replication is not a perfect process, and mistakes occur.” An error – and one not corrected by the body’s repair mechanisms – results in a tiny change in the DNA, referred to as a mutation.

Dr Cantor explains that in most cases, a pair of identical twins share the same DNA when they split. However, she continues, a recent report found that some developing twin embryos3 may already have genetic differences.

study conducted in Iceland looked at almost 400 sets of identical twins, finding that 12% of the identical twins they examined had up to 100 genetic differences. But this is still thought to be a slight difference, considering that an individual’s genetic code is huge. In effect, though identical twins don’t have identical DNA, they are genetically similar.

There can be differences between the twins because of the interactions in how the environment interacts with their genetic material. In other words, the cells in one of the twins may express their DNA one way compared with how it’s expressed in the other twin. Even though DNA can be seen as a recipe – actually a book of recipes – for everything about you, many factors can affect how the recipes are executed or expressed. It’s like having several different pastry chefs baking a chocolate fudge cake. They may rely on the same recipe, but the cakes end up a bit different because of different chef techniques, different ovens and so forth.

Even if the twins had identical DNA, the environment (even in the womb1) influences how their genes are expressed. This can lead to differences in personality, health and appearance. Scientists have found that a variety of environmental factors (such as smoking, diet, exercise and stress levels) can affect our genes by boosting the activity of a gene or slowing it down. According to Alexandria Haseley MS, a Genetic Counsellor at the Cleveland Clinic’s Genomic Medicine Institute, “A lot of research has demonstrated that genetic differences become greater as we age.” That’s because of an accumulation of errors in DNA as well as the effects of environmental factors.

adapted from endocrineweb.com

c. Do you know any twin brothers or sisters? Are they more similar or different?

1. a. Посмотрите на фото. Что у них общего?

1. b. Прочитайте статью. Какие факторы приводят к сходствам и различиям между близнецами?

1. c. Знаете ли вы братьев или сестер-близнецов? Они больше похожи или различны?

Ответ:

1. a. The two girls in the photo are likely identical twins. They have many things in common, such as their blonde hair, facial features, freckles, and they are wearing similar shirts. They appear to be the same age.

1. b. According to the article, the main factor for similarity is their shared DNA, making them genetically similar. Factors leading to differences include:
1. Genetic differences: Tiny changes or mutations in DNA can occur during cell replication, meaning even identical twins don't have perfectly identical DNA.
2. Environmental factors: The environment influences how genes are expressed. This includes factors like diet, exercise, smoking, stress levels, and even the environment in the womb. These can lead to differences in personality, health, and appearance over time.

1. c. Yes, I know a pair of twin sisters. Physically, they are very similar, and it can be difficult to tell them apart at first glance. However, their personalities are quite different. One is very outgoing and artistic, while the other is more reserved and studious. This reflects what the article says about how environment and personal experiences can shape individuals, even with similar genetics.

Перевод:

1. a. Две девочки на фотографии, скорее всего, однояйцевые близнецы. У них много общего, например, светлые волосы, черты лица, веснушки, и они одеты в похожие рубашки. По-видимому, они одного возраста.

1. b. Согласно статье, основным фактором сходства является их общая ДНК, что делает их генетически похожими. Факторы, приводящие к различиям, включают:
1. Генетические различия: Во время репликации клеток могут происходить крошечные изменения или мутации в ДНК, что означает, что даже у однояйцевых близнецов ДНК не является идеально идентичной.
2. Факторы окружающей среды: Окружающая среда влияет на то, как экспрессируются гены. Сюда входят такие факторы, как диета, физические упражнения, курение, уровень стресса и даже среда в утробе матери. Со временем это может привести к различиям в характере, здоровье и внешности.

1. c. Да, я знаю сестер-близнецов. Внешне они очень похожи, и с первого взгляда их бывает трудно различить. Однако их характеры совершенно разные. Одна очень общительная и творческая, а другая более сдержанная и прилежная в учебе. Это отражает то, о чем говорится в статье: как окружающая среда и личный опыт могут формировать личность, даже при схожей генетике.