Download A-4 Notes

Science 9: Unit A –
Biological Diversity
Topic 4: Wearing Your
Genes
Heredity and Genetics
• Heredity is the passing of
heritable traits from parents to
offspring. Genetics is the study
of heredity in species.
• Variation in a species takes two
forms:
Continuous Variations
•
Continuous Variation – There
is a gradual difference in a
certain heritable trait
between individuals. Skin
color, hair color, height, etc.
show continuous variation as
they show a range of
possibilities.
Discrete Variations
•
Discrete Variation – This is a
trait that is either one
possibility or another. Being
left or right handed is an
example of discrete variation.
Being male or female is
another example, so is your
blood type.
Dominant and Recessive
Traits
• Certain traits are dominant and
others recessive. Why? Dominant
traits tend to be more adaptive than
recessive traits.
• You get two set of genes when you
are gestating: one from your Mom
and the other from Dad. The
dominant trait always wins out and
you will have that trait.
How do People get
recessive traits?
• For example curly hair is a dominant
trait. If your mother passes the gene
for curly hair and your father passes
his gene for straight hair, you will
have curly hair.
• So how do people still have
recessive traits? The only way you
can have a recessive trait such as
lighter hair is by having been given
two recessive genes.
• Eg. blonde haired kids have received
two blonde hair genes.
Why do recessive traits
still exist?
• Why haven’t dominant traits taken
over all over the world? Because
human populations were separated
from each other for most of history.
Germans were allowed to evolve to
their environment, and Asians to
theirs. Only recently have we started
to live in mixed populations.
Nature Vs. Nurture
• While some traits such as eye color
are completely heritable, others
such as scars are determined by our
experience and environment. Still
others, such as height, intelligence,
and weight result from a complex
combination of nature (your genes)
and nurture (your environment or
experience).
Nature Vs. Nurture
• Many geneticists are trying to
find out how much of our mixed
traits are from nature and how
much from nurture. This has led
to certain people becoming very
sensitive and angry about the
findings.
Nature Vs. Nurture
• Scientists have determined that
intelligence is about 60% inherited
and 40% due to your experience.
This ratio of 60/40 is also true
(roughly) for your personality type.
• Some people feel that this will give
employers an excuse to fire people if
they don’t have the ‘right’ genetics.
• The bottom line is that there is a lot
that we do not yet know about
genetics.
Mutations = changes in
our genetic material.
• Mutations are changes to your
genetic material. Before you are
born, your genes mutate on their
own, increasing variability in our
species. Most of these mutations
are harmless, a smaller amount is
very harmful, and a tiny number of
mutations can lead to a
successful structural or
behavioural adaptations.
Mutations Cause Cancer
• Mutations can also occur during
our lifetime. Cancers are the
result of our cells mutating and
then reproducing out of control,
killing and starving our healthy
cells. 1 out of 3 people will
develop a cancer.
Mutagens Cause
Mutations
• Mutagens are forms of radiation
and chemicals which can cause
our cells to mutate (and
therefore can lead to cancer).
UV rays, X rays, and other high
energy EM waves can mutate
our cells, while chemicals in the
environment or in our food can
cause mutations.