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Darwin’s Tea Party. The Biological Revolution: DNA and Modern Genetics Winter 2009. After Mendel . Gregor Mendel (1822-1884) had discovered the basic mechanisms of heredity.

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darwin s tea party

Darwin’s Tea Party

The Biological Revolution: DNA and Modern Genetics

Winter 2009

after mendel
After Mendel
  • Gregor Mendel (1822-1884) had discovered the basic mechanisms of heredity.
  • His discoveries also strongly suggested physical or material particles were responsible for the transmission and expression of these hereditary characteristics.
the discovery of dna
The Discovery of DNA

In 1951 James Watson (1928- ) and Francis Crick (1916- ) discovered the structure of the DNA molecule - Deoxyribonucleic Acid

In this famous photograph Watson (right) and Crick (left) demonstrate a model of the DNA molecule.

the discovery of dna1
The Discovery of DNA

DNA was soon shown to be the mysterious material particle sought for since Mendel’s discoveries.

the discovery of dna2
The Discovery of DNA

Hi Mom!

DNA exists in the nucleus of almost every cell in the body, beginning from day 1 when you were just an embryo.


The DNA molecule is structured in a “double helix” shape (like two spiraling staircases).

One helix is connected to another by base pairs – shown here as “A”, “T”, “C”, “G”.

dna base pairing rules
DNA Base Pairing Rules

Base pairing rules

The base pairs, though, must connect following the base-pairing rules so that “A” connects only with “T” and “C” with “G”.

A Japanese molecule

dna sequences
DNA sequences

A DNA sequence is simply the order of base pairs along the DNA double spiral.

In this case, we note the sequence “T-A” “C-G”

dna and genes
DNA and Genes

What is a gene?

A gene is thus a segment of DNA containing varying lengths of DNA base pair sequences (T-A, C-G, G-C, T-A, etc…).

genes and proteins
Genes and Proteins
  • Different DNA sequences (genes) “spell out” different kinds of proteins.
  • Proteins are key ingredients helping to make all sorts of cells and cell functions from skin cells, to hair cells, to blood products, to various enzymes, to … you name it.
  • In this way DNA really is a blue print for how to make the proteins & enzymes that go on to make the traits of an entire body.

Actually, the route from DNA sequence to protein is a bit more complicated. First the DNA sequence spells out a certain type of amino acid and that then helps produce a certain type of protein.

genes and traits
Genes and Traits
  • Thus genetic traits, whether physical or mental can be traced back to DNA sequences.
  • This is true for “normal traits”, e.g. for hair colour, eye colour, etc… as well as for “abnormal traits”, such as some genetic diseases.
Humans have 23 pairs of chromosomes, receiving one pair from each parent.
  • Genes are located in particular locations and regions of the chromosomes.
human genome project
Human Genome Project
  • Thanks to the Human Genome Project and other endeavours to “map” the genetic code, we can now detect many genetic anomalies responsible for genetic diseases in humans.
  • Here, in specific locations of chromosomes 13 and 17, are the BRCA1 and BRCA2 mutations, responsible for some hereditary forms of breast cancer.
genes and traits1
Genes and Traits

In this example, the genetic disease sickle cell anemia can be traced back to a single genetic “spelling mistake” in the genetic sequences contained in the upper part of chromosome 11:

genetic engineering1
Genetic Engineering
  • Genetic engineering involves modifying sections of the genetic code (gene sequences) of an organism.
  • This can be done by cutting, copying, changing or inserting desired gene sequences in the genetic code.
  • Inserting of gene sequences is often done through viruses and bacteria.
genetic engineering2
Genetic Engineering

Genes can control certain traits; as in flower colour in this example.

genetic engineering using bacteria and viruses
Genetic engineering: Using bacteria and viruses

Of course, we don’t always associate bacteria and viruses with helpful effects!

Here, for example, are two unhelpful bacteria, the Tobacco Mosaic Virus and Human Immunodeficiency Virus (HIV) which produces AIDS.

The T4 bacteriophage is a virus which attack the E. coli bacteria.

gene therapy
Gene Therapy

Genetic engineering techniques can be used for altering genetic sequences responsible for genetic diseases. This is called gene therapy.

In this case, missing sequences causing Cystic fibrosis can be inserted into the genetic code of a CF patient using a virus as delivery vehicle.

genetic engineering of pharmaceuticals
Genetic engineering of pharmaceuticals

Here the gene for producing insulin is taken from a human chromosome and inserted into a bacteria’s plasmid (a single ringed chromosome). This plasmid with the human insulin gene can then be used to produce insulin to treat certain forms of diabetes.

This is one example of how genetic engineering techniques can be used to create pharmaceuticals or medicines.

genetically modified foods
Genetically modified foods

But what if we could change the genetic blue print – the genetic sequences that ultimately make up life?

genetically modified foods gmfs
Genetically Modified Foods (GMFs)

Scientists can alter genes by cutting out undesired and inserting desired sequences. In this case a gene from a bacteria called Bt which acts like an insecticide is being inserted into the genetic code of a corn plant. The corn will thus contain this built in insecticide.

http mathgeeklife blogspot com 2007 11 genetic engineering html

Catfish anyone?

genetic engineering of humans
Genetic engineering of humans?

Fears of genetic engineering often go back to the Frankenstein story.

applications of genetic technology
Applications of Genetic Technology

Thus, many applications of genetic technology exist, including:

  • Criminal forensics
  • Medical Diagnostics
  • Genetically Modified Foods/Organisms (GMFs/GMOs)
  • Gene Therapy
  • Genetic Cloning
  • Embryonic and Stem cell research
  • Tracing evolutionary history and linkages
  • Much, much more!
applications of genetic technology1
Applications of Genetic Technology
  • However, all of these technologies also confront us with serious potential for abuse and misuse.
  • The same techniques that can heal can also be used to modify organisms in ways that may not be beneficial to those organisms
  • This includes the human organism too!