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PG 30-32 GENETICS. NOTES AND VOCABULARY. Genetics - the study of heredity . Heredity - a set of characteristics received from parents. Raising useful plants and animals . Prevention and treatment of diseases . Discovering the secrets of life on Earth. Solving crimes .

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Pg 30 32 genetics



  • Genetics - the study of heredity.

  • Heredity - a set of characteristics received from parents.

Uses for genetics

  • Raising useful plants and animals.

  • Prevention and treatment of diseases.

  • Discovering the secrets of life on Earth.

  • Solving crimes.


Gregor mendel

  • Known as the “father of genetics.”

  • Was both religious and scientific.

  • Introduced this branch of science to the world by cross-breeding plants, studying traits being passed along, and producing hybrids.

Gregor Mendel

Difference between mendelian genetics and non mendelian genetics

  • Mendelian inheritance does not take account of recombination or mutation.



  • True-breeding (purebred) - an organism with parents having the same traits.

  • Hybrid - an organism with parents having different traits.

  • Genes - parts of chromosomes that “carry” traits.

  • Alleles - different forms of a gene.



  • Dominant - an allele that excludes the recessive form.

  • Recessive - an allele that is not expressed in the presence of a dominant allele.


  • Aa - HETEROZYGOUS (AKA: CARRIER - an organism that “carries” a recessive gene that is not expressed.) (different alleles)

  • aa - HOMOZYGOUS RECESSIVE (same small)


What is the difference between phenotype and genotype

  • Phenotype - displays the physical form of a trait.

    • Only what you can see when you look at an organism.

  • Genotype - displays the genetic form of a trait.

    • Only what the genes express…you may not be able to tell.

  • What is the difference between phenotype and genotype?

    Punnett squares

    • Punnett Square - a process used to determine the probability of offspring traits.

    • Probability - studies the likelihood of occurrence of random events.

    • Monohybrid - comparing one trait in a Punnett square.

    • Dihybrid - comparing two traits in a Punnett square.


    More definitions

    • Multiple alleles - a type of gene that is determined by more than 2 alleles.

    • Complete dominance - a heterozygous condition in which both alleles are partially expressed. This results in an intermediate phenotype.

    • Incomplete dominance - a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a combined phenotype.

    • Codominance - a condition in which both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other.


    Last definitions

    • Polygenic traits - traits for which the phenotype (appearance) depends on alleles in multiple genes.

    • Sex-linked traits - traits associated with a gene that is carried only by the male or female parent.

    • DNA fingerprinting - a technique to distinguish between individuals of the same species using only samples of their DNA.


    Three conclusions to his research
    Three Conclusions to His Research

    • Principle of Dominance and Recessiveness

      One allele in a pair may mask the effect of the other

    • Principle of Segregation

      The two alleles for a characteristic separate during the formation of eggs and sperm

    • Principle of Independent Assortment

      The alleles for different characteristics are distributed to reproductive cells independently.

    Mendelian genetics
    Mendelian genetics

    • Character (heritable feature, i.e., fur color)

    • Trait (variant for a character, i.e., brown)

    • True-bred (all offspring of same variety)

    • Hybridization

      (crossing of 2 different true-breds)

    • P generation (parents)

    • F1 generation (first filial generation)

    • F2 generation (second filial generation)

    • Testcross: breeding of a recessive homozygote X dominate phenotype (but unknown genotype)

    How can the chances of an offspring s traits be determined
    How can the Chances of an Offspring’s Traits be Determined?


    • Get out your Guinea Pig Dihybrid Cross

    • I will call up students to fill in one square on the example dihybrid cross on the board until we complete the problem.

    What about 2 traits
    What about 2 Traits? Determined?

    • BbLl x BbLl

    • The Gametes contain one of each of the alleles. (BL).

    • Each of the offspring contain four alleles exactly like the parents.(BbLl).

    • Notice the number of possible offspring has increased.

    • The phenotypic ratio is 9:3:3:1

    Bbll x bbll
    BbLl Determined? x BbLl

    Now on your own
    Now on your own… Determined?

    Work the Dihybrid Crosses on your own.