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Topic 5
Biological Diversity
DNA: The Secret of Life
DNA: deoxyribonucleic acid
– 1868: Johann Miescher collected DNA
from nuclei of certain cells
– 1953: James Watson and Francis Crick are
attributed with discovering the structure
of DNA
– 2003: Human Genome Project sequenced
the majority of the human genome.
DNA: The Secret to Life
Chromosomes: composed of
strands of DNA contained in
the cell’s nucleus.
– DNA is the molecule that controls
the formation of cells and all that
cells do.
– DNA is the genetic material that
passes the plan from one generation
to the next.
The Structure of DNA
DNA is a molecule found in
the shape of a coiled ladder,
referred to as a double helix.
The sides of the ladder are
made of alternating sugars
and phosphates.
The rungs are made of
nitrogen bases.
Nitrogen Bases
There are 4 types of nitrogen
bases:
– Adenine (A)
- Thymine (T)
– Guanine (G)
- Cytosine (C)
– A always forms a chemical
bond with T.
– C always forms a chemical
bond with G
DNA Structure
The Genetic Code
Bases come together in a specific
sequence.
Sequence of the DNA forms a code.
Code is a blueprint for protein
production in cells.
Protein molecules make of much of
structure of cells, they also control how
the cells are formed and how they
function.
Sections that code for a specific protein
are called a gene.
Chromosomes
Chromosomes are tightly coiled DNA.
Humans have 46 chromosomes, 23
from each parent.
Each cell in the body needs a complete
set of chromosomes. This means a new
set must be formed before cell division
can take place.
Chromosomes
Chromosome Viewer
Types of Cell Division
Mitosis: when a somatic (body)
cell divides into two identical
copies
Meiosis: when cell division
results in the formation of egg
or sperm cells.
Mitosis: Normal Cell
Replacement
Occurs for growth of organism.
Occurs repair and replacement
of tissues.
Before cells divide copies of
each chromosome must be
made. After mitosis the two
new cells are genetically
identical to each other and to
the original cell.
Mitosis
Mitosis: Normal Cell
Replacement
Some cells in body last a life
time others survive only a few
days.
Cell Type
Cell Life Span
Brain Cells
30 – 50 Years
Red Blood Cells
120 days
Stomach Lining Cells
2 days
Liver Cells
200 days
Intestine Lining Cells
3 days
Skin Cells
20 days
Meiosis: Sex Cell
Formation
Sex cells (gametes, eggs or
sperm) are the only cells in the
human body to have 23
chromosomes.
When an egg and a sperm join
to form a zygote does the new
cell have a complete set of
chromosomes.
Meiosis: Sex Cell
Formation
Meiosis starts the same way as
mitosis. Chromosomes are
copied.
The difference from mitosis is
that to form sex cells, cell division
occurs two times.
The second division results in
gametes that have half the
number of chromosomes.
Meiosis
Meiosis: Sex Cell
Formation
The random dividing of the 23
chromosomes in half creates many
possible different combinations.
The combinations can be passed to
gametes.
In zygotes when parents’
chromosomes combine there is an
increase in variation.
Technology and
Variation
Genetic Engineering: a process
developed in the last 30 years to move
pieces of DNA from one cell to
another.
This process has allowed the
movement of genes with desired
characteristics from one organism to
another.
This process is referred to as a
biotechnology.
Genetic Engineering
Genetic Engineering leads to questions
like:
– Does biotechnology “tamper with
nature”?
– Are there unknown harms to the
environment, people, or other organisms
that come with specific biotechnologies?
– What new opportunities and ways of
solving problems will advances in
science bring?
Biotechnology in
Medicine
Many developments have been made
in medicine through the use of
biotechnology.
Transgenic animals have developed
to produce human proteins required
for different medical issues.
Because of development animals do
not have to die to produce the needed
proteins.
Biotechnology in Food
Production
Genetic Engineering has
become an important part of
producing food.
Concerns have been brought
up about genetically modified
organisms and how they could
affect natural populations.