Цели и задачи:
- систематизировать знания по теме;
- развивать кругозор учащихся, знакомить их с последними достижениями в области молекулярной биологии, лауреатами Нобелевской премии в данной области;
- актуализировать знания учащихся о строении ДНК, практическое значение этих знаний;
- развивать умение работать с текстами научного характера;
- развивать умения работать со статьями специализированного словаря;
- развивать умение читать тексты научного характера с применением различных стратегий чтения.
ХОД УРОКА
“The importance of DNA is so great that any knowledge about it won’t be essential”
F. Crick
1) Teacher’s brief introduction into the talking point of the lesson
April 2003 is a particular date in the history of the world science, because on that
day it marked the 50 th anniversary of DNA discovery which is considered to be the main
molecule, and since that moment Biology as a science has turned over a new page in its
development.
Why did the discovery of the only molecule DNA, just its double helix
structure, become a turning point in Biology and lead to great
changes in this field?
By the beginning of 1950-s, it had been already known that genetic information existed on
each strand of DNA in all living organisms, and transferred inherited information. But
although the structure of DNA showed how inheritance worked, it was not still known how
DNA influenced the behavior of cells and it was unclear which way this heteropolymer,
consisting of 4 different chains, could realize its 2 main functions, such as transferring
information to the offsprings and replicating information within the cell.
It was April 1953 that made a start on the development of the molecular biology which is
still going on. There have been made a number of brilliant discoveries, lots of which were
awarded Nobel Prizes.
2) Insight the history of DNA discovery
Everything in this world has its beginning. What about this one? When and where were
the first sprouts of a new science noticed? What do we know about it? And if we know, do
we know enough?
Let’s have a look into the depths of DNA history and date back to 1865 when a Moravian
monk, Gregor Mendel by name, from a small town of Austrian Empire after studying the
nature of inheritance in plants published his work.
Some questions to the pupils:
- What do you think about inherited traits?
- Did people know about these facts many years ago?
- If yes, how could they notice these facts?
- Why did they use their practical knowledge in their daily life?
The fact that living organisms inherit traits from their parents has
been used since prehistoric times to improve crop plants and animals through selective
breeding.
But the modern science of genetics began with the work of Gregor Mendel in mid-nineteenth
century who observed that organism inherit traits via discrete units of
inheritance, which are now called genes.
Some questions to the pupils:
The word GENETICS was derived from the word GENE
- But what is genetics in your opinion?
- What does this field of science study?
Слайд
– Mendel studied the segregation of heritable traits in pea plants
– He was studying the trait for flower color
– Mendel noticed that the flowers of each pea were either purple or white, but never an
intermediate between the two colours
– These observation of discrete inheritance and segregation are known as Mendel’s
first law or the Law of Segregation
3) Match some words
Of course, Gregor Mendel was not the only person who had been interested in such
things, there were a lot of his followers who had studied his work and made their own
discoveries.
But before coming across dates and experiments connecting with this great discovery,
let’s touch upon some important scientific definitions that will help us to understand
the way of discovery itself better.
Read the words (1-10) in the column on the left with their definitions (A—J) on the right. Translate into Russian.
4) Johan Friedrich Mescher
Some years later, after Gregor Mendel’s discovery, in 1869 at the laboratory of one of the German Universities, another scientist Johan Friedrich Mescher, a Swiss physician and biologist isolated various phosphate-rich chemicals, which at first he called nuclei (now nucleic acids) paving the way for the identification of DNA as the carrier of inheritance.
Слайд. Только портрет Мишера (без информации)
APPENDIX 2 (Let’s investigate Mescher’s biography) Текст «Выбери нужное слово», затем информация учителя с опорой на второй аналогичный слайд с портретом и информацией
A bit later, when Mescher discovered that nuclei possessed acid
properties he gave it the name of nucleic acid.
Mescher and his students researched much of the nucleic acid chemistry, but their function
remained unknown for a long time.
The significance of the discovery first published in 1871 was not at first appreciated, as
the biological function of this new substance was not clear and for a long time
DNA was considered to be a store of phosphorous in a living organism.
Moreover, even at the beginning of the XX th century many biologists believed that DNA had
nothing in connection with inheritance, because according to them, DNA had been too
monotonous and had not been able to contain coded information.
However, Mescher’s discovery played an important part in the identification of nucleic
acids as the carriers of inheritance, and only thanks to another German scientist the
research was carried out on the chemical structure of nuclei.
5) The XX th century brought us the other brilliant
names of the scientists who had been working in this field.
In most cases they were British and American biologists but it doesn’t matter at all, as
their discoveries belong not only to the countries they were from, but to the whole world.
This list of names is too long even for a simple mention, but we have to recollect some of
them, whose discoveries were the most prominent and one of the first names is William
Astbury, an English physicist and molecular biologist. He was the first who
X-ray diffraction studies of biological molecules, and although Astbury was unable to
propose the correct structure of DNA, but his ideas of X-ray diffraction in 1937 led
directly to the work of Maurice Wilkins and Rosalind Franklin, and from there to Double
Helix DNA structure by Francis Crick
and James D. Watson in 1953.
But long before 1953 there was another date of 1944, when Oswald Avery, a
biologist from Britain, one of the first molecular biologists and a pioneer in
immunochemistry, made his discovery having said that DNA is the material of which
genes and chromosomes are made.
Inspired by Avery’s discoveries another researcher, Oswald Chargaff
from Columbia University, the USA identified the molecule of DNA as the basis of heredity.
He made 2 main discoveries, which are known all over the world as Chargaff’s rules.
6) Francis Crick, Rosalind Franklin, Maurice Wilkins, James D. Watson
The scientific process is interactive. It is possible to start one’s own research at
any stage, formulating one’s own hypothesis, adopt or deduce one’s own predictions or
to go on with the experiments made by someone else. The same thing happened to Francis
Crick after his returning to Britain to the laboratory of King’s College,
London, where his friend Maurice Wilkins had been working, and where he
made up an original plan for Rosalind Franklin especially, who was
interested in DNA as well. Later James D. Watson joined them because the
problem of learning how genetic information might be stored in molecular form interested
him, too.
But what do we know about Francis Crick and Maurice Wilkins besides they have been friends
for a long time?
Let’s read short texts and get some information about these scientists.
Слайды + Тексты для учащихся (обсудить тексты после проверки, что Вы узнали для себя нового?)
Read the text attentively and say what these dates meant in Maurice Wilkins' lifetime
8) Well, we have to mention the name of Rosalind Franklin
whose understanding of basic chemistry let her reveal a mistake
in the first model of DNA built by Wilkins and Crick and which was absolutely wrong in her
opinion.
We don’t know exactly how these two scientists managed to use Rosalind’s data on DNA,
but they saw more benefits in the joint work together with James D. Watson, so when they
all were jointly awarded Nobel Prize in 1962, Rosalind Franklin’s name was not even
mentioned, besides she did not live up to that glorious day as Rosalind Franklin, A
British biophysicist, chemist, biologist died in 1958 at the age of 38.
But the world science admits Rosalind Franklin as the creator of the single X-ray
diffraction image that made critical contribution to the understanding of the fine
molecular structures of DNA and RNA
9) Gene Therapy
a) Life goes on and new generations of scientists that are keen on
molecular biology make their research nowadays.
Gene therapy is still in its infancy, but this technology has been used with some success.
Gene therapy is the insertion of genes into an individual cell and biological tissues to
treat disease, such as cancer where deleterious mutant alleles are replaced with
functional ones.
b) As for Alec Jeffreys, British geneticist, he developed techniques for DNA fingerprinting and DNA profiling which are now used all over the world to assist police detective work.
10) Hymn to DNA
Well, I won’t be mistaken if I say that DNA is really the main molecule of life and who knows may be one day some of you will discover new aspects of this fantastic molecule and, may be other pupils and other teachers will be speaking about your discovery, because as it was said at the beginning of the lesson
The importance of DNA is so great that any knowledge about it won’t be essential
Some years ago we had a similar lesson on DNA in one of the 11 th grades, and they made up синквейн about this molecule. Read only two of them and try to make up your own.
Литература:
- Энциклопедия для детей, ТОМ 2 «Биология», Издательство «Аванта +», ЗАО «Контакт РЛ», Москва, 2002.
- Е.С.Музланова, Е.И.Кмсунько «Тесты. Английский язык», 10—11 классы, Москва, ООО «Астрель», 2003.
- Л.И.Романова «Английский язык. Будь готов к Единому Государственному Экзамену», АЙРИС-ПРЕСС, Москва, 2005.
- Tom Hutchinson “Hotline, Intermediate”? Oxford University Press,1993.
- Olga Afanasyeva, Virdginia Evans, Victoria Kopylova “Practice Exam Papers for the Russian National Exam” (Единый Государственный Экзамен, Тренировочные задания. Английский язык), CenterCom, Express Publishing, 2007.
- А.Д.Браун, М.Д.Фаддеева «Молекулярные основы жизни».
- Virginia Evans, Jenny Dooley, Olga Podolyako, Julia Vaulina “SPOTLIGHT-8”, Expres Publishing — Prosveshcheniye, 2008.
- Браун А.Д., Фаддеева М.Д. «Молекулярные основы жизни», М.: Просвещение, 1976 (сайт www.musci.ru)
- Л.Л.Киселев «К 50-летию открытия структуры ДНК» (сайт http://vivovoko.rsl.ru)
- Материалы сайтов www.wikipedia.org , http://biozoo.ru , www.natureworld.ru