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Chapter 4: Heredity
Section1- Genetics
Life Science
Lesson Plan
Inheriting Traits

Create a short list of characteristics
about yourself…
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
down… but what are
genes?

Genes - Sections of DNA on a
chromosome.

Genes on chromosomes control the
traits that show up in an organism.
– There are hundreds of genes on a
chromosome

Alleles are different forms of a trait
that a gene may contain.
– There are TWO alleles for every trait

Example: Height
– 1 allele is tall (T)
– 1 allele is short (t)
Alleles
alleles
a gene
GENETICS

Genetics- the study of inherited traits.
 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

Mendel used pollen from both Tall and
Short Plants to pollinate by hand the
flowers.

Cross-Pollination- the pollination of
two different plants together

http://www2.edc.org/weblabs/Mendel/
MendelMenu.html
Hybrid vs. Purebred

3.Purebreds- offspring that receives
two of the same alleles for a trait (TT
or tt)
Hybrid vs. Purebred

4. Hybrids- offspring that receives
two different alleles for a trait (Tt)
OR……
Check out these
websites!

http://www.switcheroozoo.com/zoo.ht
m

http://www.buildyourwildself.com/
2 Types of Alleles
a. Dominant allele- covers up or
dominates the other trait.
Represented by a CAPITAL
b. Recessive allele- the trait seems
to disappear
Represented by a lower case
Homozygous vs. Heterozygous

Homozygous – an organism with 2
alleles for one trait that are the
same (written TT)
6

Heterozygous – an organism with 2
alleles for one trait that are different
(written Tt)
Phenotype vs. Genotype

Genotype- the genetic-makeup of an
organism (types of letters used)
Phenotype vs. Genotype


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.

For example, Male and Female
Chromosomes
Check out the
Punnett Square
Screencast!
Chapter 4
Part 2- Genetics Since
Mendel
Life Science
Question…

If you crossed Purebred Red fouro’clock plants with Purebred White
four-o’clock plants, what would the
offspring look like?

Actually… they were Pink !?!?!
 Incomplete
Dominance- when
two homozygous parents
combine, the offspring results in a
mixed (or blended) phenotype
 Remember
the chickens?!?!

When neither allele for a trait is
Dominant.

The phenotype produced is a blending
between the two homozygous parents.
– The combining of Purebred Red &
Purebred White produced PINK plants.

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 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

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…Eye Color, Hair
Color, Skin tone, & Handspan are
traits produced by a combination of
genes.

Human Genes &
Mutations

What are Mutations?!?!?
Mutations
 Mutations
- a permanent
change in the DNA sequence
A
mutation can be harmful,
beneficial, or cause no effect.
Chromosome Disorder
 Chromosome
disorders- caused
by more or fewer chromosomes
than normal
–Downs Syndrome- caused by
an extra chromosome (trisomy)
at Chromosome 21
Recessive Genetic
Disorders

Recessive Genetic Disorders are
disorders passed through the
Recessive alleles.

Both parents contain the recessive
allele (containing the disorder) that
comes together in the offspring.
 When
both parents are
Heterozygous, they do not show
any symptoms
– (Called “carriers” for the trait.)

Example- 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 and
Hemophilia

Pedigree- used to follow or trace traits
through generations of a family.
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
