Download Lesson 4.1 Power Point

Face
Shape
Eye Color
Nose-
Hair 
HAIR
Patterns of Heredity
During sexual
reproduction a cell
containing genetic
information from the
mother and a cell
containing genetic
information from the
father combine into a
completely new cell,
which becomes the
offspring.
In Humans, the 23rd pair
of chromosomes are the
sex chromosomes. A
human female has two
X-Chromosomes and the
male has one Xchromosome and one Ychromosome.
So what is Heredity?
Heredity is the
biological process
whereby genetic factors
are transmitted from
one generation to the
next. Traits are passed
from parents to
offspring.
Inherited traits Vs. Acquired traits
A sun burn is an acquired
trait…you are not born with
one.
Scars are also acquired.
--------
What determines the traits you inherit from your parents?
A gene is a unit of heredity
that occupies a specific
location on a chromosome
and codes for a particular
trait. Individuals inherit their
genes from their parents.
These genes code for hair
color, eye color, detached
ear lobes etc.
* Each chromosome consists of a thread of DNA coiled up tightly.
*DNA contains genetic information called genes.
*Alleles are various forms of the same gene.
The gene at the bottom of this image codes for height. The capital H is for regular
height and the lower case h is for short height.
The Genotype is the name for the genes an organism has.
Sometimes your genes contain information the is not
expressed physically. This is your complete heritable
genetic identity.
*An
organism’s phenotype describes
the actual characteristics that can be
observed. (Brown eyes, red hair,
widows peak, dimples, height,
diseases)
The Phenotype is the gene that is expressed
and observable.
*Widows Peak 
Detached Earlobes

Rolling tongue
Red Hair 
So how do I end up with certain phenotypes?
Some genes are dominant
A dominant allele is one that
is expressed in the
phenotype even if only one
copy is present in the
genotype.
And others are recessive
A recessive allele is one that
is expressed in the phenotype
only when two copies of it are
present.
For example…..
E = Unattached earlobe
e = Attached earlobe
****Capital letter= dominant
Lower case= recessive
Detached
Earlobes are
a dominant
trait:
EE or Ee
* Remember that you get these genes (E or e) from your parents
Attached
earlobes are
recessive:
ee
Gregor Mendel and his Pea Plants
Mendel was a monk
who lived in Austria
during the mid 1800s.
Before he became a
monk, he attended
university and received
training in science and
mathematics. Mendel
is well-known for his
experiments in
genetics with pea
plants.
Crossing a true-breeding
regular pea plant with a
true-breeding dwarf pea
plant produces all regular
pea plants in the first
generation.
Allowing the first
generation pea plants to
self-pollinate resulted in
about three-fourths regular
pea plants and one-fourth
dwarf pea plants.
Mendel also experimented
with different traits in the
plants like flower and pod
position, seed shape, seed
color and flower color. His
experiments showed similar
patterns of heredity.
Gregor Mendel realized that
each plant must have two
“factors” for each possible
trait. Those things called
“factors” are what we now
call genes and alleles.