首页
登录
职称英语
The Cloning TechnologyI. The difference
The Cloning TechnologyI. The difference
游客
2023-11-24
32
管理
问题
The Cloning Technology
I. The difference between a【T1】________colony and cloning a mammal
A. Clarify the illusion: scientists have been cloning genes for years.
B. Definition of clone: a clone is population of cells produced by【T2】________; all the cells in a clone have exactly the【T3】________, using a process known as "recombinant【T4】________
technology".
C. Clone a mammal: "nuclear transfer".
II. Genes, chromosomes and the genome
A. Genes
- DNA—its【T5】___________makes it divide easily.
-【T6】________of chemical groups within DNA form genes.
- Genes determine what【T7】________a given cell will have.
B. Chromosomes: genes are linked together to form chromosomes.
C. Genome: the entire collection of chromosomes in each cell.
D.【T8】_______________genes enables scientists to mass-produce proteins that can be used to【T9】_______________.
III. The process of cloning a gene
A. Remove DNA from the cell.
B. DNA is cut into pieces using【T10】_________.
C. To replicate DNA, attach them to nonmammalian DNA.
D. Plasmids are easily incorporated into【T11】______ and multiply by themselves.
E. The plasmid carries the gene into a【T12】________ cell.
F. The gene【T13】________a plasmid and some proteins.
G. The plasmid【T14】________.
H. Copies passed to the cell’s【T15】_________.
I. Each cell contains one or more copies of the recombinant DNA molecule. The gene is now considered cloned. [br] 【T10】
The Cloning Technology
Today, we are going to talk about the cloning technique. First, we will see the difference between a single cell colony and cloning a mammal. Then we will focus on cell cloning process and its scientific use.
In March 1997, the world said "hello" to Dolly, the first mammal to be cloned from an adult cell. We asked ourselves: Would the world soon be populated with human clones? Did you know that cloning isn’t new? In fact, scientists have been cloning genes for many years in laboratories around the world. Of course, cloning a gene and cloning a whole mammal are quite different in terms of process and product. But just how do you get from a single cell to a clone?
We generally think of cloning as producing a duplicate of something. Scientists, however, usually use the term clone in referring to cells. A clone is population of cells produced by one ancestor. Because of the way cells multiply, all the cells in a clone have exactly the same genetic makeup. Gene cloning uses a process known as "recombinant DNA technology". By contrast, cloning a mammal, such as the sheep Dolly, involves a technology known as "nuclear transfer". Although the end result is the same, the actual processes of gene cloning and mammalian cloning are quite different. But we need to start from the beginning to understand how these complicated and amazing bioengineering technologies evolved.
Now, we will study on what genes, chromosomes, and the genome are.
Within the body of a mammal, tissues are made of cells. Inside each cell is a long molecule called DNA. Its shape enables it to divide easily. Arrangements of chemical groups within DNA form genes. Genes direct cells to produce proteins, and thus determine what function a given cell will have. For example, skin cells produce proteins which are present in skin tissue, and blood cells produce a protein present in blood. Genes essentially tell each cell what type it is. Genes are linked together to form chromosomes. The entire collection of chromosomes in each of your cells is called genome. All the cells in your body contain the same genome. Once you realize that all cells contain the information for making the whole organism, you know that cloning is theoretically possible.
But what makes a skin cell different from a blood cell? The chromosomes within the nucleus of each cell are folded in various ways. Genes that are buried within the chromosomes are inactive, or switched off, while genes on the surface of the chromosomes are active. In a skin cell, the genes for producing skin proteins are active, while in a blood cell, the gene is active. Gene cloning is the process of producing a population of cells all of which contain a specific gene. Using these identical cells, scientists can study the entire genome and obtain clues to how genes are switched on and off.
Cloning genes also enables scientists to mass-produce proteins that can be used to treat a variety of diseases. For example, the cells in the pancreas produce a protein called insulin which is important in helping the body maintain appropriate blood sugar levels. Some people have a disease called diabetes because their cells don’t produce enough insulin. Cloning the insulin gene has provided a way of producing large amounts of human insulin which is used to treat diabetes.
Then, we are going to disclose the mystery of cloning a gene. To clone a gene, scientists remove the DNA from a cell, isolate the specific gene of interest, and then get it to multiply. Sound simple? Not so fast. Let’s look at each step.
First the DNA must be removed from the cell. Over the years scientists have perfected chemical methods for doing this, based on the physical properties of DNA molecules. The DNA is then cut into pieces using special proteins. You may think of these special proteins as little knives programmed to cut the DNA in specific places. By using the correct special proteins, scientists can isolate whatever gene they want.
Once the gene is isolated, it can then be duplicated. Mammalian genes do not reproduce by themselves, however. To replicate them, scientists attach them to pieces of non-mammalian DNA that do replicate on their own. The most common procedure uses small circular pieces of DNA called plasmids that come from bacteria. Plasmids have two useful characteristics. They are easily incorporated into bacteria; they multiply by themselves inside bacteria. The gene of interest is combined with a plasmid and some proteins. The proteins open the plasmid circle and stitch in the new gene. The result is a recombinant DNA molecule. The plasmid carries the gene into a host cell. Once inside the host, the plasmid multiplies, making lots of copies of itself and the gene it contains.
When the host cell divides, copies of the recombinant DNA molecule are passed to the cell’s offspring. As the bacterial cells continue to divide, a colony of identical cells is produced. Each cell contains one or more copies of the recombinant DNA molecule. The gene is now considered cloned.
Let’s go back now to the example of the insulin gene. Prior to cloning this gene, scientists purified insulin from animal sources, like pigs or cows. Scientists isolated the insulin gene from the DNA of human pancreatic cells. Then they attached the insulin gene to a plasmid and were able to get bacterial cells to incorporate the recombinant DNA. The result was a colony of bacteria that continually produced human insulin—a little insulin producing factory!
选项
答案
special proteins
解析
细节题。根据讲座内容“The DNA is then cut into pieces using special proteins.”可直接得出答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3216168.html
相关试题推荐
PASSAGETWO[br]Howdidtheauthorthinkofthebookonthedifferencesbetween
PASSAGETWO[br]Howdidtheauthorthinkofthebookonthedifferencesbetween
Thereareafewdifferencesintheorganizationofmemorandumsandletters.
Thereareafewdifferencesintheorganizationofmemorandumsandletters.
WhatCanWeLearnfromArt?I.IntroductionA.Differenceb
WhatCanWeLearnfromArt?I.IntroductionA.Differenceb
WhatCanWeLearnfromArt?I.IntroductionA.Differenceb
WhatCanWeLearnfromArt?I.IntroductionA.Differenceb
WhatCanWeLearnfromArt?I.IntroductionA.Differenceb
WhatCanWeLearnfromArt?I.IntroductionA.Differenceb
随机试题
AmazinglyfortheBritish,wholovequeues,thereisnoformalline-up—theb
WhattoDoIfYouSuspectaFoodAllergy1.Consequencesoffoodallergy30,
Untiltheinventionofthemodernwashingmachine,mostpeoplewashedtheir
抗震建筑楼板开洞尺寸的限值为()。A.不大于楼面宽度的10% B.不大于楼
正常人手指末节掌侧皮肤的两点区分试验距离为( )。A.1~2mm B.2~3
灶心土的主要作用是A.增强补脾止泻的功能 B.增强活血化瘀的作用 C.增强止
预防接种中度反应是A、局部反应红肿直径的大小2.6~5.0Cm,发热(腋温)37
列宁说:“意识到自己的奴隶地位而与之作斗争,是革命家;没有意识到自己的奴隶地位而
商业银行主要运用( )确定资产回报水平、结构配置、风险控制等要素,确保各项计划目
在高处作业要求中,安全绳长度不应超过()m。A.6 B.5 C.2
最新回复
(
0
)