red - Di seguito viene proposta un'attività per il CLIL di Scienze in lingua inglese sul tema del DNA. Le attività prevedono la produzione scritta, la comprensione del testo e l'associazione dei termini alle esatte definizioni. Alla fine del testo sul DNA è presente un glossario dei termini.
1) Do you look like your parents? Which characteristics do you think you inherited from them?
2) Look at the title of the text and the picture. Why do you think the writer describes DNA as 'a very large molecule’? Now read the text and check your answer.
DNA — a very "large" molecole
From the beginning of time, humanity has wondered how certain characteristics could be passed on from one generation to another. Deoxyribonucleic acid (DNA), the material which programmes many of our physical and psychological traits, was first identified in 1869 by the Swiss scientist Friedrich Meischer. But it was not until 1953 that the molecular structure and distinctive double helix shape of DNA was known. Discovered by Francis Crick and James Watson, this was the real breakthrough that has made advances in molecular biology possible.
DNA is the best known of a series of acids called nucleic acids. These acids are made up of smaller nucleotide molecules. A nucleotide has three parts:
- a sugar molecule
- a phosphate group
- a base containing nitrogen
There are tour types of base: adenine, guanine, thymine, and cytosine. These are sometimes abbreviated to A, G, T, and C. It is the bases that contain hereditary information. A series of nucleotides is called a polynucleotide chain. DNA consists of tvvo of these polynucleotide chains.
The interconnections betvveen these tvvo chains, which keep them together, are hydrogen bonds. The tvvo interconnected chains form themselves into the shape of a double helix.
Chromosomes are the biological carriers of hereditary information. DNA is stored in Chromosomes in the nucleus of ceIIs. Inside human ceIIs there are 46 pairs of Chromosomes, 23 pairs supplied by each parent.
Crick and Watson’s discovery marked the arrival of molecular biology and genetic engineering, and the modern day uses of DNA in industry, medicine, solving crime and agriculture.
has wondered - si è domandata
helix - elica
made up of - composti di
chain - catena
bond - legame
carrier - portatore
3 Match the words from in the text [1 —5] to the definitions [a-e].
1 _ molecule a) genetically transmitted or passed on
2 _ traits b) the tiny structures in the celi nucleus that carry biological information
3 _ breakthrough c) the smallest part of a chemical compound
4 _ hereditary d) a sudden important discovery or development
5 _ chromosome e) a genetically-determined charateristic
4 Answer the questions.
1 What does DNA stand for?
2 What did Crick and Watson discover in 1953?
3 What function do A, G, T, and C have?
4 What do Chromosomes do?
5 How is Crick and Watson’s discovery used today?