Transcript Science 9 Topic 4 Wearing Your Genes

Biological Diversity and
Survival
Topic 4
Wearing Your Genes
Wearing Your Genes
Why do some people
have blue eyes?
What makes some
people red-heads and
others brunettes?
Are some people born
great musicians, or do
their talents simply
develop with practice?
Wearing Your Genes
The answer
is Genetics
Wearing Your Genes
Genetics:
–The study of
genes or
heritable traits
–Genetics 101
Part 1: What
are genes?
Did You Know…?
About 70 percent of the
population carries a gene that
allows them to taste bitter
flavours, research shows. For
the other 30 percent, aspects of
bitterness just don’t register at
all. According to the study’s
authors, the ability to taste
bitter flavours may have helped
people avoid poisonous plants
or berries in the wild.
Did You Know…?
Roughly 20 to 30 percent of all
people are genetically coded for
the “photic sneeze reflex,”
studies have found. What does
that mean? When your eyes are
exposed to sudden, bright
sources of light, you sneeze.
Spend a couple minutes in a
dark bathroom, then step out
into bright sun or overhead
lights. If you achoo, you carry
this dominant gene.
(Researchers aren’t sure why
this happens)
Two Kinds of Inherited
Variation
Continuous Variation:
– In genetics, traits that show a range of
possibilities
– Ex. Skin colour, height, hair colour etc.
Two Kinds of Inherited
Variation
Discrete Variation:
– In genetics, inherited
traits that have a limited
number of variations.
– Ex. The ability to roll
one’s tongue, whether or
not someone will have
hitchhiker’s thumb or the
lack of an earlobe.
– There are only two
possibilities when dealing
with discrete variations
Dominant or Recessive
Children inherit their genes from both parents, however
they do not always show their parents’ traits
– Ex. During sexual reproduction, traits like tongue
rolling are passed from parents to offspring. If one
parent gives the characteristic for tongue rolling and
the other parent gives the “non-roller” characteristic,
the child will be able to roll his or her tongue. Tongue
rolling is an example of a “Dominant” characteristic.
Dominant or Recessive
Dominant Trait/Characteristic:
– An inherited trait that shows up in the
offspring
– Ex. Polydactyly, skin pigmentation, brown
hair etc.
Dominant or Recessive
Recessive
Trait/Characteristic:
– An inherited trait that
shows up in the
offspring only if both
parents passed on the
genes for the trait
– When mixed with
genes for a dominant
trait, a recessive trait
does not show up in
the offspring
– Ex. Blue eyes, the
white hair of a
Kermode bear.
Bikini Bottom Genetics
Nature vs. Nurture
Not all characteristics are
inherited
Some characteristics depend
entirely on the environment
– Ex. Scars, injuries, clothing,
hairstyle, makeup and even
cosmetic surgery.
Nature vs. Nurture
Some characteristics are due to
a combination of both genetic
and environmental factors
– Ex. A persons weight is due to
genetics, diet and activity level
Nature vs. Nurture
For many years
there has been a
debate about
whether or not a
person’s genetics
(nature) or a
person’s
environment
(nurture) will define
their characteristics
Nature vs. Nurture
One of the best
known ways to
prove either
argument is to look
at identical twins
that have been
separated at birth
and raised in
different
environments
Nature vs. Nurture
Ex. In one case, two identical twins
were separated at birth and reunited
later on in life only to find that they
were both volunteer fire fighters,
both sported moustaches and both
wore similar looking glasses
Separated Twins
Twins Separated at Birth
Changing Our Genetic
Information
Even our genetic code
can be changed by
factors in the
environment and by
random errors
These changes to our
DNA are called
“mutations” and are
often caused by
“mutagens”
Changing Our Genetic
Information
Mutations:
– A change in the genetic
information, or DNA, of an
organism
Mutagens:
– An agent that can cause
changes in the genetic
information of an organism
– Ex. X-rays, ultraviolet rays,
cosmic rays toxins etc.
Changing Our Genetic
Information
Sometimes mutations will have
little or no effect on an
organism, but often they can
disrupt the complex
interactions of chemicals and
cells that are necessary for life.
Changing Our Genetic
Information
Mutations and Cancer:
– Some mutagens can cause
mutations that have the ability to
turn normal cells into cancerous
cells
– These mutagens are called
“Carcinogens”
Changing Our Genetic
Information
Ex. Spending too
much time in the
sun without proper
protection can
cause UV light
damage to the DNA
in your skin cells.
These mutations
can sometimes lead
to skin cancer
known as
melanoma.
Changing Our Genetic
Information
Mutations and Reproduction:
– Mutations that occur in the DNA of
reproductive cells (ie. Sperm or Eggs)
may be passed on from parent to child
– These mutations can create extra
variation in a population and can be
beneficial, however, the majority of
these mutations are usually
unfavourable
Heredity and Traits