Bionodo I - Introducción. Historia de la Genética

Uploaded by bionodo on 21.09.2012


Introduction: The history of genetics.
Every living being on Earth
is made of cells, us included.
Cells are like microscopic membranous balloons that have inside
thousands of chemical compounds that interact
with each other in a complex and precise way.
That interaction is in essence what keeps us alive.
This cells
can live on their own as a single-cell organism
or associate to create incredibly complex
pluricellular entities.
For example, plants,
fungus or animals.
There is a huge variety of cells and because of that
we are able to process the food we eat
and grow,
move, think and sense the environment.
How does a cell know what to do and when,
where is it in your body, how to respond to an stimulus
or when to divide?
All that a cell is
and has to do is written inside in a molecule
called desoxyrribonucleic acid (DNA).
DNA is a thin, long fiber
The mechanism of action of the DNA is one of the greatest
wonders in the Universe.
Does a tomato have genes?
-..And a cucumber?
- And a transgenic?
-A transgenic even more, doesn't it?. But transgenics aren't good.
-Yes -And a transgenic?
-A transgenic too. But they have been changed.
-In addition the transgenic has its genes modified.
- Yes, because....Okey, let's think. Think about that tomato.
- I didn't study genetics.
- I liked it. Genes, genes...
Wait, we're thinking.
-Does a tomato have genes?
- That is that stuff about Darwin and the peas. - A tomato, I don't know...I think so.
- Wait, let's think.Does a tomato have genes?
What is the DNA?
-The DNA is...the book where is written how we will be when we're born.
How are our proteins going to be.
Then there is the copy, the RNA, and there is our genetic burden.
There are the chromosomes, the 21st chromosome that gives Down's Syndrome...
-Is like a book where is written how are we going to be.
-Before the tomato there was another tomato, but it was not like the other tomato.
- It must have something genetic. - Hey Miss, does a tomato have genes?
What are the genes? -The genes...
Genes are...
those things that are transfered from parents to sons...I suppose.
Aren't they?
-Yes, yes. A tomato has genes.
-And a transgenic?
-A transgenic...That is "tuned", that is "doped".
What is mitosis? - Mitosis is...
the name of the process in which
a cell is divided into two cells.
- Very well. And the meiosis?
- Meiosis is like mitosis but with other kind of cells
that I can't remember right now, but is different.
-That is full of hormones...
-Of course, it must have genes.
- Yes, because you put in it good genes
from other tomato so that we can get a tasty tomato. A great tomato from the orchard.
- No, no. You put genes in it so that
the tomato is more beautiful, not tastier.
-That is another point altogether.
-Cells change, I don't know.
The genes, and DNA...I don't know.
-That's a great contribution, really. -Thank you.
As you see, everyone has a general idea about what is the DNA, the genes and the genome.
But people often ignore to what extent the genetic material defines the life of each living being on our planet,
including plants, microorganisms and animals.
In this series
we want to go in depth
in this topic so that everyone can learn the secrets
of molecular biology.
The history of DNA.
The Swiss scientist Miescher
was the first to study the DNA without really
knowing what he was facing.
He discovered that inside the cells there are molecules with a lot of
phosphate which he called nucleins.
Years later
a German called Kossel studied the nature of the nucleins
and he discovered that they had a proteic part and a
non-proteic, acid part he called nucleic acid.
Furthermore, we can see him as the discoverer of the nitrogenous bases, one of the
basic parts of the structure of these molecules that constitute the DNA.
Following this train of research Levene describes
this molecules in more detail
stablishing that apart from the bases
that Kossel discovered, there are sugars and phosphate molecules .
He was the first to suggest that nucleotides are joined by phosphate.
But why is the DNA molecule so important?
Because it comprises all the genetic information.
The author of this revelation was Avery, a Canadian scientist from the
early 20th Century.
Before it was thought that the proteins codified
this genetic information
that is inherited from parents to sons through generations.
Avery's theory was backed up by the experiments of the scientists
Hershey and Chase.
They consisted of the staining of virus with radioactive
phosphorus and sulfur.
Specifically, of essential components of the DNA
and proteins.
This experiment shows that the DNA gets into the cell
and that's why the DNA (and not the proteins) contains the
necessary information to cause the infection of the bacteria.
In 1953, a year after the completion of the Hershey-Chase experiment,
Watson and Crick
published in Nature the discovery of the double-helix structure of the DNA .
The proof that allowed the elucidation of the secondary structure of the DNA
was the famous photo 51, taken by Rosalind Franklin.
Her boss, Wilkins, showed this photo to Watson and Crick without her permission,
making it possible for them to work out the structure of the
DNA, for what they were granted the Nobel Prize. Not only for them, but also
for Wilkins. Franklin dies years before the presentation of the Prize, and her
contribution to this step forward in science was forgotten
for a long time.
In this first episode we have seen what people know about biology
and we have reviewed the history of genetics.
See you in our next episode.