Chapter 4 heredity section1 genetics
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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 .

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Chapter 4: Heredity Section1- Genetics

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Chapter 4: HereditySection1- Genetics

Life Science

Lesson Plan

Inheriting Traits

  • Create a short list of characteristics about yourself…


  • Heredityis 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)


a gene



  • Genetics- the study of inherited traits.

  • Gregor Mendel-The Father of Genetics “The Man”

Gregor Mendel

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


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)


Check out these websites!



2 Types of Alleles

a. Dominantallele- 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)


  • 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 4Part 2- Genetics Since Mendel

Life Science


  • If you crossed Purebred Red four- o’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 threephenotypes 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 - 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 recessiveallele (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

  • Advances in Genetics

    A. Genetic Engineering- experimentations that changes the arrangement of DNA that makes up a gene.


  • Recombinant DNA

  • Inserting a useful section of DNA into a bacteria

  • Example- Creating Insulin (Page 143)

  • 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.

  • 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







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