About two – three weeks ago ethical problems around cloning aroused my student’s interest in the topic. We began to study it within our lesson of technical or professional English. However, we very quickly found out that basic knowledge of genetics is quite necessary to be able to understand the essence of the problem. So, the text below has appeared. I hope the text will launch the the discussion the issue that concerns everybody. Thank you in advance for your contribution. G.Vitkova
We learn English studying and discussing real issues
Genetics studies genes, their function, structure and interaction. Genes enanle living organisms to inherit features from their ancestors. Genetics attempts to identify which features are inherited, and explain how these features are passed from generation to generation.
In genetics, a feature of an organism is called a “trait“. There are many trait types, and these range from aspects of behavior to resistance to disease. Traits are often inherited, for example tall and thin people tend to have tall and thin children. But the interaction between inherited features and the environment may influence the final result. For example a child might inherit the tendency to be tall, but if little food is available and the child is poorly nourished, it will still be short.
Genetic information is encoded via a long molecule called DNA which is copied and inherited across generations (see the picture above). Traits are transferred in DNA as instructions for creating and operating an organism.
These instructions are contained in segments of DNA called genes. The order of genes in DNA makes up the genetic code. This is similar to the sequence of letters forming words. The organism “reads” the sequence of these units and decodes the instruction. Different forms of one type of a gene are called alleles of that gene. As an example, one allele of a gene for hair color could comprises the instruction to produce a lot of the pigment in black hair. Another allele could give a garbled version of this instruction, so that no pigment is produced and the hair is white.
A long molecule that looks like a twisted ladder. It is made of four types of simple units and the sequence of these units carries information, just as the sequence of letters carries information on a page (see picture on the left).
They form the rungs of the DNA ladder and are the repeating units in DNA. There are four types of nucleotides (A, T, G and C) and it is the sequence of these nucleotides that carries information.
A package for carrying DNA in the cells. They contain a single long piece of DNA that is wound up and bunched together into a compact structure. Different species of plants and animals have different numbers and sizes of chromosomes.
A segment of DNA. Genes are like sentences made of the “letters” of the nucleotide alphabet, between them genes direct the physical development and behavior of an organism. Genes are like a recipe or instruction book, providing information that an organism needs so it can build or do something – like making an eye or a leg, or repairing a wound.
The different forms of a given gene that an organism may possess. For example, in humans, one allele of the eye-color gene produces green eyes and another allele of the eye-color gene produces brown eyes.
The complete set of genes in a particular organism.
When people change an organism by adding new genes, or deleting genes from its genome.
Genes are copied each time a cell divides into two new cells. The process of copying DNA is called DNA replication.
DNA can be copied very easily and accurately because each piece of DNA can direct the creation of a new copy of its information. This is because DNA is made of two strands that pair together like the two sides of a zipper. The nucleotides are in the center, like the teeth in the zipper, and pair up to hold the two strands together.
When DNA is copied, the two strands of the old DNA are pulled apart by enzymes which move along each of the two single strands pairing up new nucleotide units and then zipping the strands closed. As a result two new pieces of DNA appear. Each of them contains one strand from the old DNA and one newly made strand. This process isn’t perfect and sometimes the wrong nucleotide may be put into the new strand. It causes a change in the sequence of the gene. These changes in DNA sequence are called mutations. Mutations produce new alleles of genes. Sometimes these changes stop the gene from working properly. In other cases the mutations can change what the gene does or even let it do its job a little better than before. These mutations and their effects on the traits of organisms are one of the causes of evolution.
Since traits come from the genes in a cell, putting a new piece of DNA into a cell can produce a new trait. This is how genetic engineering works. For example, crop plants can be given a gene from an Arctic fish, so they produce an antifreeze protein in their leaves. This can help prevent frost damage. Other genes that can be put into crops include a natural insecticide from the bacteria Bacillus thuringiensis. The insecticide kills insects that eat the plants, but is harmless to people. In these plants the new genes are put into the plant before it is grown, so the genes will be in every part of the plant, including its seeds. The plant’s offspring will then inherit the new genes, something which has led to concern about the spread of new traits into wild plants.
The kind of technology used in genetic engineering is also being developed to treat people with genetic disorders in an experimental medical technique called gene therapy. However, here the new gene is put in after the person has grown up and become ill, so any new gene will not be inherited by their children. Gene therapy works by trying to replace the allele that causes the disease with an allele that will work properly.
The National Human Genome Research Institute (NHGRI) created the Talking Glossary of Genetic Terms to help people without scientific backgrounds understand the terms and concepts used in genetic research. Simply click on the term of interest to open a page with a wealth of information, including the term’s pronunciation, audio information, images and additional links to related terms. Students, teachers and parents will find the glossary an easy-to-use, always available learning source on source on genetics. For more information go to the Guide to the Talking Glossary:
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