Transcript Genetics and Heredity

 Heredity
is the
passing of traits
from parents to
offspring.
 Genetics is the
overall study of
genes and heredity.
Kind of like how
Biology is the study
of living things.
Gregor Mendel is
known as the father of
Heredity. He was an
eastern European
monk and studied pea
plants.
 Gregor Mendel was
born in 1822 in the
Czech Republic.
 Gregor Mendel had an
“interesting”
childhood.
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Mendel found that
certain characteristics
of pea plants were
passed on from the
parent plants to the
offspring. These
characteristics or
genetic traits were
caused by factors that
we now call genes.
Traits are simply
characteristics that an
organism has. Gregor
Mendel experimented
with observable traits
or characteristics.
 Each trait can be is
controlled by at least
two genes. Traits can
be dominant or
recessive depending
upon the genes that
make them up.

Dominant Traits-The
strongest trait, this trait
is always visible if
there is at least one
dominant gene.
 Recessive Trait-The
weakest trait, this trait
is often not visible. For
a recessive trait to
show up it has to be
expressed by two
recessive genes.
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The following is a list of
genetically inherited
traits you get from your
parents.
 Color Blindness
 Cystic Fibrosis
 Down Syndrome
 Hemophillia
 Sickle Cell Disease
 Some forms of Cancer
 Being Bald
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We use the letters of the
alphabet as gene
symbols to represent
genes.
Every characteristics is
caused by at least two
genes.
Gene symbols are
chosen by using the first
letter of the strongest or
dominant trait for both
genes. For example if
the dominant trait for a
flower as to be yellow the
gene symbol would be Y.
A
capital letter is
used for the strong
trait (gene) and a
lower cased letter is
used for the weak
trait.
 A strong trait is called
dominant and a
weak one is called
recessive.
Whenever a dominant
gene is present, it
shows itself, but it takes
two recessive genes
(together) to show
themselves.
 When two genes are
exactly the same for a
trait, they are called
purebred. When they
are not the same they
are called hybrid.
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The phenotype refers to
the visible expression of
the genes, or what can be
seen with the naked eye.
The genotype is the
actual gene make-up of
the organism.
Blending, co-dominance,
or incomplete
dominance all refer to
genes where neither
gene is dominant or
recessive.
 Alleles
are the
different forms of
genes. Two alleles
for each gene are
inherited, one from
each parent.
 Genotype is the
actual gene make-up.
Both of the alleles
together. Example
TT, Tt, or tt.
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Phenotype is what you can
see or the visible
expression of genes. Like
brown eyes, being tall, ear
size, etc.
Purebred is when the genes
are the same for a trait.
Organisms that are
purebred often times have
the same trait show up in
each new generation.
Another word for purebred
is homozygous.
Individuals can be
homozygous dominant or
homozygous recessive.
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Hybrid is when genes
are mixed. This is when
individuals have on
dominant and one
recessive gene. The
dominant gene or trait
expresses itself and
shows up. Another term
for hybrid is
heterozygous.
Probability is the
mathematical chance that
something will happen.
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Incomplete dominance
or co-dominance is a
rare instance when no
gene dominates and a
mixture of the two traits
shows up as the trait of
the offspring. For
instance, in roses, a red
rose crossed with a
white rose produces a
pink rose.
 We
often times use
Punnett Squares to
organize all the
possible
combinations of
offspring from
particular parents.
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In flowers yellow is
dominant over white. A
white homozygous
recessive flower is
crossed with a yellow
homozygous flower.
What are the genotypes
and phenotype
probabilities for this
hybrid x purebred cross?
Let’s start with the
basics…………
 PBS Video
 1.
Instructions for a
Human Being.
 3. One Wrong Letter