Chapter 4: Heredity
Section1- Genetics
Life Science
Lesson Plan
Inheriting Traits

Create a short list of characteristics
about yourself…

What is another name for these
characteristics?
 TRAITS
Heredity

Heredity is the passing of traits from
parents to offspring.

Inherited Traits- Traits that are
passed from parents to their offspring
(through fertilization)
Genes are passed… but
what are genes?

Genes are sections of DNA on a
chromosome.

These genes on chromosomes control
the traits that show up in an organism.
– There are thousands of genes on a
chromosome

Alleles are different forms of a trait
that a gene may contain.
– There are 2 alleles for each gene
– 1 from mom and 1 from dad

Example: Height
– 1 allele is tall
– 1 allele is small
Alleles
alleles
a gene
B. Genetics- is the study of inherited
traits.
1. Gregor Mendel- The Father of
Genetics “The Man”
Mendel’s Experiment

Mendel studied the traits of Pea Plants
– Look Page 105

Crossed 2 Plants with different
expressions of the trait
– Example- Tall (T)& Short (t)
– Round R & Wrinkled r
Mendel’s Experiment

When the plants were crossed he
discovered that the new plant formed
looked like one of the two parents.
Take
a look…
Mendel’s Tall vs. Short Plants
VOCABULARY

3. Purebreds- offspring receives the
two same alleles for a trait (TT or tt)
VOCABULARY

4. Hybrids- offspring receives two
different alleles for a trait (Tt)
2 Types of Alleles
a.Dominant allele- covers up or
dominates the other trait
Represented by a Capital Letter
b. Recessive allele- the trait seems
to disappear
Represented by a lower-case letter


“Homo”zygous – an organism with 2
alleles for one trait that are the
same (written TT)
“Hetero”zygous – an organism with 2
alleles for one trait that are different
(written Tt)
 Genotype-
the geneticmakeup of an organism (types
of letters used)
Phenotype- the way an organism
physically looks/behaves as a result
of its genotype.
 Types of Words used: Tall, Short,
Blonde, Brown, etc.

The Use of
Punnett Squares

A Punnett Square can help you predict
what an offspring will look like.
“What’s the Probability of the
baby’s gender?”

A Punnett Square can help you
predict what an offspring will look like
1. Monohybrid: Offspring of parents
that differ in only one genetic
characteristic
Monohybrid Cross:
GG x gg
DYHIBRID CROSSES
2. Dyhybrid: Offspring of parents that
differ in TWO genetic characteristic
***USE FOIL to separate the combinations
F – FIRST
O – OUTSIDE
I – INSIDE
L – LAST
DIHYBRID EXAMPLE
Tall & Green
TtGg
x
TtGg
DIHYBRID EXAMPLE #2
Brown hair vs Blonde hair
AaBb
x
aaBb
Chapter 4
Part 2- Genetics Since
Mendel
Life Science
Question…

If you crossed Purebred Red fouro’clock flower with Purebred White
four-o’clock flower, what would the
offspring look like?
 Actually…
they were PINK!?!?!

Incomplete Dominance- when two
homozygous parents combine, the
offspring results in a blended
phenotype

Combining Purebred Red & White
and produced Pink

Neither allele for a trait is Dominant.

The phenotype produced is mixed
between the two homozygous parents.
– The combining of Purebred Red &
Purebred White produced PINK plants.
What would happen if you crossed a
Red horse and a White horse?
PINK!?!?!
Just kidding…
ROAN

Although Mendel studied peas that
were controlled by two alleles, many
traits can be controlled by more than
two alleles…
Multiple Alleles

A trait that is controlled by Having
more than two alleles is controlled by
Multiple Alleles.

Traits controlled by Multiple Alleles
produce more than three phenotypes
of that trait.
Example (Flip to Page)

Example of Multiple Alleles…
 Blood
Types: A, B, AB, and O.
– The O allele is recessive to both A and B
Other Worksheet…

Phenotype A - AA or AO Genotype

Phenotype B – BB or BO Genotype

Phenotype AB – AB Genotype

Phenotype O – OO Genotype
Polygenic Inheritance

Polygenic Inheritance- when a group
of gene pairs acts together to produce
one trait.
– Which creates more variety in
phenotypes
What would be an
example?

Many traits such as…Skin Color, Eye
Color, Hair Color, and Handspan are
traits produced by a combination of
genes.
Human Genes &
Mutations
 Mutations:
a permanent change in
the DNA sequence

A mutation can be helpful, harmful, or
cause no effect.
Mutations
Chromosome disorders- caused by
more or fewer chromosomes than
normal
 Downs Syndrome- caused by an
extra copy of chromosome 21

Recessive Genetic
Disorders

There are human genetic disorders
that are caused by Recessive Genes.

How could this occur?

Both parents contain the recessive
allele

Because parents are Heterozygous,
they do not show any symptoms
– (Called “carriers” for the trait.)

Cystic Fibrosis is a homozygous
recessive disorder.
Sex-Linked Disorders

An allele inherited on a sex
chromosomes ( X or Y ) is called a
sex-linked gene.

Inherited conditions are linked with the
X and Y chromosomes.

Example- Color Blindness is a sexlinked disorder caused by recessive
allele on the X chromosome.
Where did you get your
genes from?
Pedigrees
 Pedigree-
used to follow or trace
traits through generations of a family.
No… not the dog food…
Section 3
III.
Advances in Genetics
A. Genetic Engineeringexperimentations that changes the
arrangement of DNA that makes up
a gene.
Types:
1.
Recombinant DNA

Inserting a useful section of DNA into
a bacteria

Example- Creating Insulin (Page
143)
2.


Gene TherapyWhen a “normal allele” is placed into
a virus, the virus then delivers the
normal allele when it infects a
specific cell. (Figure 13 Page 144)
May be used to control Cystic
Fibrosis and other disorders.
3.


Genetically Engineering PlantsPlants are created by genetically inserting
the desired genes of one plant into
another plant you want to show those
genes.
Also genetically engineered: ANIMALS

“Cloning”
Works Cited
www.coolclips.com
 http://kentsimmons.uwinnipeg.ca/cm15
04/mendel.htm
 www.classzone.com
 www.dkimages.com
 www.virtualsciencefair.org
 www.scienceray.com
