Clone science.Directions: Read "Medical Milestone," pp. 8 to 12. Then study this diagram to answer the questions that follow. [ILLUSTRATION OMITTED] CREATING A CLONE Recently South Korean scientists became the first team to create a stem cell line A stem cell line is a family of constantly-dividing cells, the product of a single parent group of stem cells. They are obtained from human or animal tissues and can replicate for long periods of time in vitro ("within glass"; or, commonly, "in the lab", in an artificial from a cloned human embryo. Here's how they did it: 1 REMOVE NUCLEUS Hwang cut a small hole in a woman's egg and gently squeezed out its nucleus, which holds a cell's DNA DNA: see nucleic acid. DNA or deoxyribonucleic acid One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. . 2 TRANSFER DNA An adult cell, with its own nucleus and full set of DNA, was injected into the empty egg. 3 START DIVISION A calcium injection tricked the egg to divide and grow. This early stage of embryo development took place in a nutrient-rich petri dish pe·tri dish n. A shallow circular dish with a loose-fitting cover, used to culture bacteria or other microorganisms. Petri dish a shallow, circular, glass or disposable plastic dish used to grow bacteria on solid media such as agar. . 4 NURTURE CELL GROWTH After a week, the egg grew into a blastocyst--a hollow ball Of about 100 cells. No previously cloned embryos have grown larger than six or eight cells. 5 ISOLATE STEM CELLS Scientists removed the outer cell layer and grew the inner cell mass in·ner cell mass n. The mass at the embryonic pole of the blastocyst concerned with the formation of the body of the embryo. in a petri dish to form a stem cell line, or group of continuously dividing cells. 6 FORM TISSUE The stem cells could form the three basic tissue types present in the human embryo. Ectoderm ectoderm, layer of cells that covers the surface of an animal embryo after the process of gastrulation has occurred. This outer layer, together with the endoderm, or inner layer, is present in all early embryos. outer tissue, like skin. Mesoderm mesoderm, in biology, middle layer of tissue formed in the gastrula stage of the developing embryo. At the end of the blastula stage, cells of the embryo are arranged in the form of a hollow ball. : middle tissue, like muscle. Endoderm endoderm (ĕn`dədûrm'), in biology, inner layer of tissue formed in the gastrula stage of the developing embryo. At the end of the blastula stage, cells of the embryo are arranged in the form of a hollow ball. : inner tissue, like organ linings. [ILLUSTRATION OMITTED] 1. Which of the following steps occurs first? a. growing the inner cell mass in a petri dish. b. injecting the egg with calcium. c. coaxing the stem cells to form skin. d. injecting an adult cell into an empty egg. 2. Which tissue type forms muscle? a. ectoderm b. mesoderm c. endoderm d. none of the above 3. In order to clone an embryo, Hwang's team removed the egg's -- and replaced it with --. a. DNA, the inner cell mass b. blastocyst blastocyst /blas·to·cyst/ (-sist) the mammalian conceptus in the postmorula stage, consisting of an embryoblast (inner cell mass) and a thin trophoblast layer enclosing a blastocyst cavity. , a new nucleus c. nucleus, the outer cell layer d. nucleus, an adult cell 4. Researchers spiked the egg with calcium in order to a. prompt the cell to divide and grow. b. stop the cell from dividing. c. transfer an adult cell into the egg. d. feed the cell. 5. What was the end result of Hwang's cloning procedure? a. a single cloned cell b. a single cloned stem cell line c. an embryo d. organs ANSWERS 1. d 2. b 3. d 4. a 5. b |
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