Jag hittade en hög 3,5:or i källaren – disketter från anno dazumal. Ni vet såna som Steve Jobs lärde oss sluta använda när han lanserade den blågröna iMacen 1998. Eftersom jag faktiskt har en molijox med USB-koppling som kan läsa såna skivor satte jag mig ner för att se vilka förlorade pärlor det fanns att återupptäcka.
Det fanns faktiskt en hel del som jag saknat, särskilt på en av skivorna. De äldsta filerna visade sig vara daterade 1990. Alla skivor gick för övrigt inte att läsa.
The title of my lecture is "To read from the book of life" © how to interpret
the language of the DNA.
I believe that everyone knows today that the genes are made up from DNA, and
that this elusive substance is in someway forming a code or a language that
describes our properties.
WHAT WE WILL LEARN
I will give a short introduction to this strange world. In twenty minutes, you
will hopefully know the following:
© how we could say that all living creatures is a large family, and basically
functioning by the same principals.
© that proteins isn't just something that is healthy to eat.
© how to read the alphabet in which the genes are written.¡++C¡
DIFFERENT FORMS OF LIFE
All living creatures, great and small, are made up from cells. A cell is a world
in it self, and actually the smallest organisms ©© like bacteria and yeastfunghi
©© are made up from only one cell. Humans, though, is made up from millions and
millions of cells of different types ©© nerve cells, liver cells, muscle cells
and so. If the body is a society, the cells are the households, or the
This picture shows a liver cell. As you can see it's a little world of is own.
Let's concentrate on this structure. That is the nucleus, the core of the cell.
From this safe shelter the genes are controlling the life of the cell.
As I said the cells of our body could be looked upon as biochemical factory.
Like a real factory ©© i.e. Gambro ©© it's dependent of a lot of tools and
So is the cell. The tools and machines of the cell are the proteins. On this
picture some of the functions of proteins are shown.
The most important group are the enzymes, that function as catalysts for
chemical reactions in the body. This picture represents the antibodies that
chase intruders in the body, like bacteria. This is hemoglobin that transports
oxygen in the read blood cells.
Proteins differ a lot from each other in size and structure. Now, my question
is: where do we find the descriptions for all these proteins? Where is the
information for their structure hidden? Or to put it another way: where is the
I guess that you have guessed the answer: in the nucleus. And to make a long
story short: a gene is simply a description of a protein.
To understand how all this works, we'll have to take a closer look at the
structure of the proteins. Though they can take many different forms and
functions, they all have the same basic buldingblocks, namely amino acids.
These form a chain © you could say that proteins are like a pearl necklace,
where every pearl is an amino acid.
On this picture you can see 20 different amino acids, with different
properties ©© some are big and some are small, some are acidic and some are
alkaline. As a matter of fact there are no more. These twenty amino acids are
the building blocks of the proteins in any living organism.
This overhead shows the bacteria killing enzyme lysosyme. As you can see it is
made up by a long row of amino acids. In the squares you can see the
abbriveation for an amino acid.‘2 3 3 3ÿÿ‘åThe protein molecules are not flat of course. Once they are formed they
spontaneously curl up like this necklace, forming a tree©dimensional structure.
So, what we need to describe a protein, no matter how complicated, we will just
need some 20 different letters or codes. Remember that the morse code, that only
dontains short beeps and long beeps, can transmit all the different letters of
the alfabet. Another example are the binary system of computers, working with
only the signals 1 and 0. This suggests that the code of the DNA could be rather
simple. Let us turn to the DNA and have a look at its structure.
The chromosoms, that carry our genes, are made up from DNA. The DNA is a very
large molecule © about 2 meters long. In the same way that i can can carry 200
meters of thread in my pocket if i roll it up on a cotton reel, the DNA is
packed in to the cell nucleus in a very complicated way like this picture
The DNA itself has the shape of a spiral staircase. Each step of this stair
could be one of four different so called nucleotides © adenosin, thymin, cytosin
and guanin. But let us forget this cemical language, and simply look upon the
DNA as a long row of letters, namely A, T, G and C in different combinations.
THE GENETIC CODE
Remember that I mentioned the morse code. The genetic code functions a little
different. The letters are read three at a time, and each combination
corresponds to an amino acid. There are 64 different triplets. This picture
shows the universal genetic code that functions in the same way in any living
organism © plants, animals, microorganisms.
How is this DNA©information translated into a amino acid sequence? Well, the DNA
is a reference library, and it is not used directly by the protein bulding
macines of the cell. Instead a copy is made of the gene that should be
translated into a protein, a so called messenger©RNA, chemically a bit different
tham the DNA, but practically containing the same information.
The messenger RNA is transported from the nucleus, and then the protein is
synthesized following the information of the RNA molecule.
Or let's put it like this: the book of recipies is not to be moved outside the
library. Therefore, a copy is made that can be used in the kitchen.
First, we understand that all organisms are related, as their genes are written
in the same, biochemical language.
Second, we have learned that the proteins is a family of very sophisticated
molecules, that can function in a variety of ways.
And last, we now know that the language of the genes is made upp from four
letters, that in combinations of three define a certain amino acid.
TAKE HOME MESSAGES
1. All living organisms are made up from cells
2. The essential family of functional substances in the cell are proteins.
3. Proteins are made up from a sequence of amino acids with different
4. The structural information for the proteins is given by the DNA, where one
gene corresponds to one protein.
5. Four "letters" A, T, G and C, form the genetic code. Three letters, a
triplet, corresponds to one aminoacid.
6. From the DNA a RNA copy is made that is used as a recipy by the "protein
factories" of the cell.