3,5-tummaren 1: En ytterligt genomarbetad lektion

Här kommer den första antikviteten, nämligen en föreläsning som jag höll när Gambro skulle värva en International Coordinator of Education 1992; det är ingen överdrift att hävda att det handlade om en avgörande punkt i mitt liv. Det som slår mig är hur mycket jobb jag har lagt ner för att fullända föreläsningen. Visst är det viktigt att göra sitt bästa vid en rekrytering, men här kan jag känna närvaron av den osunda perfektionism som plågade mig under mina år som forskare. Den som sett mig föreläsa under senare år vet att jag knappast är så här strukturerad nu för tiden. 

TITLE

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

factories.

A CELL

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.

PROTEIN FUNCTIONS

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

machines. 

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

cook book?

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.

PEPTIDE CHAIN

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.

AMINO ACIDS

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.

LYSOSYME

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.

CHROMOSOME

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

suggests. 

DNA STRUCTURE

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.

DNA©RNA©PROTEIN

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

properties.

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.