Download Mendel and heredity

 Mendel
was an Austrian monk
during the 1800s, that studied
the genetics of pea plants.
 Mendel is considered the
father of genetics.
 He
chose to work with pea plants
because they reproduce sexually,
which means they need male and
female sex cells.
 Mendel made three key decisions
when it came to this experiment:
◦ He had control over breeding.
◦ Chose only purebred plants.
◦ Studied traits that were either or, not a blending.
 Mendel
had to transfer pollen
from one plant to another, this
is called making a cross.
 Mendel
came up with 2 laws the
first is the law of segregation.
 The law of segregation comes in
2 parts:
◦ Organisms inherit 2 copies of each
gene, 1 from each parent.
◦ Organisms donate only 1 copy of each
gene in their gametes.
 Why
is Mendel considered the
“father of genetics?”
 Genes
are pieces of DNA that
provide a set of instructions to
cells to make a particular
protein.
 Each
gene has a particular spot on
a specific chromosome.
 An allele is any possible variation
of a particular gene.
 An
example of a gene is “eye
color”
 An example of an allele is
“Brown eyes”
 Dominant
allele are the alleles
that are expressed when an
organism is a hybrid.
 They are always expressed with a
capital letter.
◦ Example: Tt the capital T represents a tall
allele. Also, the organism will be tall,
because the capital T is dominant.
 Recessive
alleles are the alleles
that are hidden when an organism
is a hybrid.
 They are always expressed with a
lower case letter.
◦ Example: Tt the small t represents a
short allele. Also, the organism will
be tall, because the small t is hidden.
 Factors
other than genes
effect the way an organism
looks.
 poor nutrition, lack of sun,
water or shelter can effect an
organisms phenotype.
 What
is the difference between
a gene and an allele?
 There
are different names for
gene combinations.
 Homozygous
◦ Means same genes
◦ Either
 BB (homozygous (dominant) Brown eyes)
the letters are the same
 bb (homozygous (recessive) blue eyes)
the letters are the same
 Heterozygous
◦ Means different genes
◦ Bb (heterozygous Brown eyes) the
letters are different
 How
do the color of your eyes
compare to your parents or
other family members?
 Why
can’t a person be
heterozygous recessive?

A genome, is a map of all of the genetic
information an organism has.
A
genotype generally refers to
the genetic combination of 1
trait for an organism.
◦ An example would be: BB (which are
the genes that will yield a specific
color)
A
phenotype generally refers
to the physical appearance of
1 trait for an organism.
◦ An example might be: Sam has
brown eyes.


Which one can you tell right away by looking
at a person? Genotype or Phenotype?
Explain.
A
Punnett square is a system
for predicting all possible
genotypes resulting from a
cross.
 The parents alleles go along
the top and left hand edges of
each box.

P: The parent generation of which
the original cross is made

F1: The first generation of offspring
resulting from the cross

F2: The second generation of
offspring (usually a result of the F1
crosses)
 monohybrid
◦ Mono=one
A
cross
monohybrid cross shows a
cross that examines the
inheritance of a single trait.

TTxtt

TTxTt

Tt x Tt

Do a punnett square for a short woman and
a heterozygous tall man.
 Dihybrid
◦ Di=two
A
cross
Dihybrid cross shows a cross
that examines the inheritance
of 2 different traits.
 Mendel’s
second law:
 The law of independent
assortment:
◦ Allele pairs separate independently
of each other during gamete
formation.
◦ Different traits are inherited
separately from each other (twister).
 Probability
is the likelihood
that a particular event will
happen.
 Predicts average; not exact.
 Frequency / outcomes