Chapter 4: HereditySection1- 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

Allelesalleles

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 Allelesa. Dominant allele- covers up

or dominates the other traitRepresented 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 genetic-makeup 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 EXAMPLETall & Green

TtGg x TtGg

DIHYBRID EXAMPLE #2Brown hair vs Blonde hairAaBb x aaBb

Chapter 4Part 2- Genetics Since

Mendel

Life Science

Question… If you crossed Purebred Red four-

o’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 sex-linked 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 Engineering- experimentations 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 Therapy- When 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 Plants- Plants 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