This grammar exercise is designed for class 9 and class 10 students. It tests your ability to use different tense forms correctly. Complete the following sentences with the most appropriate form of the word given in the brackets.
Answers are given below.

Tenses Exercise for Classes 9 and 10

The United Kingdom …………………….. (become) the first country in the world to allow scientists to create human-animal embryos for research purposes. The research ……………………… (ban) elsewhere including the US, Australia and Canada.

The research ………………….. (involve) transferring nuclei containing DNA from human cells to animal eggs that have had nearly all their genetic information ……………………….. (remove). The resulting embryos are, therefore, mostly human, with a small animal component. Stem cells, which can …………………. (grow) into different kinds of tissue, are then …………………… (harvest) from these embryos. The embryos could give researchers a large supply of stem cells to work with. Scientists have, until now, ………………….. (rely) on human eggs left over from fertility treatment, which are in short supply and often of poor quality.

The cybrids will ………………….. (create) by using an empty or de-nucleated cow or rabbit cell filled with an adult human cell. The reconstituted one-cell embryo will ………………………. (allow) to develop for a few days in the lab and once it …………………… (become) a ball of a hundred or so cells, embryonic stem cells will …………………….. (derive) from it to study genetic diseases and the effects of the drugs.

Answers

The United Kingdom has become the first country in the world to allow scientists to create human-animal embryos for research purposes. The research is banned elsewhere including the US, Australia and Canada.

The research involves transferring nuclei containing DNA from human cells to animal eggs that have had nearly all their genetic information removed. The resulting embryos are, therefore, mostly human, with a small animal component. Stem cells, which can grow into different kinds of tissue, are then harvested from these embryos. The embryos could give researchers a large supply of stem cells to work with. Scientists have, until now, relied on human eggs left over from fertility treatment, which are in short supply and often poor quality.

The cybrids will be created by using an empty or de-nucleated cow or rabbit cell filled with an adult human cell. The reconstituted one-cell embryo will be allowed to develop for a few days in the lab and once it becomes a ball of a hundred or so cells, embryonic stem cells will be derived from it to study genetic diseases and the effects of the drugs.

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