Transcript GENETICS AND YOU

GENETICS AND
YOU
define heredity as the
passage of genetic
instructions from one
generation to the next
generation.[7.14A]
A long time ago…
•
The first recorded ideas of offspring “inheriting”
features from parents...
Aristotle
* observed common facial features
of family members -basis for artistic
styles, etc.
Born: 384 BC
Died: 322 BC
* theories included the passing of scars
and internal injuries from parent
to children
•
Charles Darwin
*Announcement of the theory of natural selection
1858
members of a population who are better adapted to the
environment will survive and pass on their traits.
* (1859) Published The Origin of Species.
famous text cataloging the many adaptations
and variations among same/similar species
fueled the (controversial) theory of evolution
See Darwin’s Finches!-->
Darwin’s Finches
The science we call Genetics
* is the study of heredity
- passing of traits from parent to offspring
•
- has more than one theory (“point of view”)
--> most common/accepted is
Mendelian Genetics
Mendelian Genetics is based upon the research of
Now credited as the
“Father of Genetics”
Mendel is most famous for his experiments with the
pea plants (Pisum sativum)..
Flowering plants can be either
self or cross-pollinated
Plus, they reproduce quickly
AND have a fast LIFE CYCLE
So What does it all mean to me?
• First you need to realize you are ½ of your
mom and ½ of your dad.
• One gamete (reproductive cell) is 23
chromosomes for humans
• ALL other cells in your body have 46
chromosomes
• It all starts with your conception and the
passing of their genes to you.
First you need FERTILIZATION
Male sperm cell
Female egg cell
..with half of “dad” DNA
…with half of “mom” DNA
•
+
They become one
…fertilized cell with a complete
Set of DNA
FERTILIZATION, Continued
The cell then begins to divide
Your first two
months!
Chromosomes!!!
..at this point all present and accounted for
•
Humans should have 46 chromosomes
The fertilized egg cell is now a
ZYGOTE
• tiny threadlike structures in nucleus of cell
•
* contain sections of DNA = GENES
*humans---> 50-100,000 genes
How does it all fit together?
Cell
Nucleus
Chromosomes
DNA
Genes
4. Some genes are dominant,
while others are recessive.
• “Stronger” traits
are called
dominant.
• “Weaker” traits are
called recessive.
• Geneticists use
symbols (letters) to
represent the
different forms of a
gene.
Dominant traits are represented by
a capital letter.
•
Yellow seeds are
dominant……..
Y
Recessive genes (for the same trait) are
represented by THE SAME lower case letter.
•
Green seeds are
recessive… lower
case y.
Dominant (yellow) =
Y
Recessive (green) =
y
•
In pea plants,
tall is dominant
• over short.
The letter used
to represent
the tall gene is
T.
• The short gene
is represented
by t.
Tall =T
Short = t
In humans, brown eyes are
dominant over blue.
Brown = B
Blue = b
5. Dominant genes hide recessive
genes when both are inherited by
an organism.
• Y + y = yellow seeds
(yellow is
dominant)
• T + t = tall plant
(tall is dominant)
• B+ b = brown eyes
(brown is
dominant)
A PUREBRED organism has two of
the same genes for a trait.
TT = purebred
TALL
tt = purebred
SHORT
A HYBRID organism has two
different genes for a trait.
Tt = hybrid TALL
(tall is dominant.)
Bb = hybrid for black
feathers (black is
dominant.)
Will a hybrid human with the genes
Bb have brown or blue eyes?
• Bb = Brown eyes
• The dominant gene (brown), will be
expressed in a hybrid.
Why must all blue eyed people be
PUREBRED for that trait?
•
• If the dominant gene is present, it will always be
expressed.
• The only possible gene combination for blue
eyes is
bb.
These basic laws of inheritance control
the traits of all living organisms on
Earth.
•
Can behavior be inherited too?
• Scenario 1 – Chimpanzee A has a very good
technique for getting a banana out of a tree. This
chimpanzee has an offspring which is taken
away and raised in isolation. The offspring is not
able to get the banana out of the tree.
• Scenario 2 – Bird A has a very specific way that
it makes its nest. The bird has several offspring.
One of the offspring is taken away and raised in
isolation. The offspring begins making a nest in
the exact same way as its parent.
• Scenario 1 is a learned behavior that a
parent would pass on through teaching.
• Scenario 2 is an example of a behavior
being inherited genetically
• Can you think of any examples of
INHERITED behavior?