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3. The Expression of GeneticInformation
4. The HumanGenome
5. Genetic Engineering
• Are located on chromosomes
• Are the basic units of inheritance that carry genetic information
• Consist of DNA (deoxyribonucleic acid)
In 1953 Watson and Crick proposed the double helix model of the DNA molecule.
Their discovery was based in one X-ray picture taken by Rosalind Franklin. However,
only Watson, Crick and Wilkins were awarded with the Nobel prize in 1962, when she
had already died because of ovarian cancer.
Rosalind Franklin. Picture 51
A molecule of DNA is formed from units called NUCLEOTIDES
Nucleotides join together through the phosphate building a strand
(a chain of nucleotides)
DNA is made up of two chains of nucleotides. Both chains are joined together
through the nitrogenous bases.
The link between bases follows the next pattern:
A and T are complementary
G and C are complementary
The two strands are twisted around each other in the shape of a double helix.
It is packed inside the nucleus.
Video doble helix structure Watson and Crick: https://www.youtube.com/watch?v=VegLVn_1oCE
Phase S Replication
2. Replication of Genetic Information
After mitosis every daughter cell receives an identical
copy of the mother cell’s genetic information.
For this to happen, the DNA needs to copy itself before
mitosis begins (phase S).
Replication is the process by which DNA duplicates itself.
https://www.youtube.com/watch?v=5qSrmeiWsuc 3DNA Replication Cartoons
https://www.youtube.com/watch?v=TNKWgcFPHqw 4DNA replication 3D
Replication must be very precise. Otherwise, mutations could appear.
Different enzymes (like DNA-polymerase) perform the replication.
1. The double helix opens up and the two strands separate.
2. New complementary nucleotides are attached to each of the bases of both strands,
forming two new strands.
3. At the end, there are 2 identical copies of DNA. Each one has a strand from
the original DNA and a new strand.
This is why it is called SEMICONSERVATIVE REPLICATION
Page 127 activity 2, 3, 5, 6, 7, 9, 10
3. The Expression of Genetic Information
Proteins are made up of molecules called amino acids.
There are 20 amino acids which make up all proteins.
Proteins have structural and physiological functions and they are
the molecules responsible for the characteristics of the body.
A gene is a piece of DNA that contains the information to
synthesize a specific protein.
B. RNA (ribonucleic acid)
It is made up of nucleotides, but instead of thymine there is Uracil.
Copy of the
information that is
in a specific part of
made up of RNA
Transfer RNA (tRNA)
It transports the
amino acids to the
This process is performed in two stages:
Transcription (It takes place inside the nucleus)
DNA cannot leave the nucleus.
The specific piece of information needed is copied onto another molecule:
The double helix of DNA opens
Only one DNA strand is copied.
A RNA strand is produced.
The mRNA leaves the nucleus
and arrives to the cytoplasm.
The double helix of DNA opens up.
Only one DNA strand is copied.
RNA polymerase synthetizes the RNA reading 3’ 5’
and creates the new RNA always 5’3’
T - A - C - G - G - C - T - A - C - A - T - G
Example of transcription:
Activity: Write the corresponding RNA sequence
Transcription (by the RNA polymerase)
A - U - G - C - C - G - A - U - G - U - A - CmRNA
mRNA leaves the nucleus and arrives to the cytoplasm.
Translation (It takes place in the cytoplasm, in the ribosomes)
The ribosome translates the information carried on the mRNA into a chain of
amino acids (protein).
1. mRNA positions itself on a ribosome, starting with its 5’ side .
2. tRNA transports free-floating amino acids in the cytoplasm to the
ribosome, in the order indicated by the mRNA.
It reads the nitrogenous bases in groups of three (codons).
3. Each tRNA is specific to an amino acid.
4. The ribosome moves along the mRNA and joins amino acids together in
the appropiate order.
Each amino acid is coded by one or more codons.
https://www.youtube.com/watch?v=gG7uCskUOrA 5 From DNA to Protein
It is the relationship between the sequence of nitrogenous bases
in DNA and the amino acids in the corresponding protein.
• It is universal
• Every living being uses the same mechanism.
• The ribosomes can read every mRNA, although it does not
belong to this cell.
• The same amino acid can be coded by more than one codon.
• All proteins start with Metionine, this means every specific
mRNA has a starting point which is AUG.
• There are some codons which code for “stop”.
Activities 11-20 (all) page 131
Write the sequence of the protein synthesized from the next DNA:
1st step: transcription mRNA
2nd step: translation protein
4. The Human Genome
The genome is the organism’s complete set of genes.
In order to know
someone’s genome we
have to know:
The whole sequence
of nitrogenous bases
function of all the
In 2003 the sequence of nucleotides
in the human genome was located.
• Diagnosis of genetic disease
• Gene therapy (modify genes)
• Medicines which can be personalised
5. Genetic Engineering
It consists of techniques to manipulate genetic material in order to change
an organism’s traits.
1. Location of the gene.
2. Isolation of the gene using restriction enzymes, which cut the DNA in specific
3. Introduction of the gene in a vector (bacterium or virus) to transport it.
Vector’s DNA + the gene = RECOMBINANT DNA
4. Insertion of the recombinant DNA into a cell in order to be expressed.
Uses of genetic
victims of crimes
Suspects and victims of crimes
Risks of genetic
• Modified organisms could
spread and reach the
nature and human beings
• Seed control by
• Possible allergies to new
It is the technology which uses living beings to create improved
Making bread, dairy
products, alcoholic drinks
Making vaccines and
Treating rubbish or
A. Agriculture and farming
Cloning: obtaining genetically identical organisms
Dolly was the first mammal to be cloned(1996)
https://www.youtube.com/watch?v=-Qry1gYYDCA Dolly the Sheep
Genetically modified organisms:organism (animal, plant…) which
has a gene from another organism so that it can express a new trait.
Bt gene is a gene belonging to a bacteria which
produces resistance to some insects.
It the plant carries it it cannot be eaten by insects.
B. Biomedical Uses
Production of insuline, antibiotics, vitamins…
https://www.youtube.com/watch?v=_ob1c-n_oNY&list=PL4473936D327B7C69 Genetic Engineering 7
Wonders of the Microbes
prevention of genetic diseases substitution of defective genes before
they are transmitted to the gametes.
gene therapy curing genetic diseases, like cystic fibrosis