Dominance - Loudoun County Public Incomplete Dominance •Codominance. Incomplete Dominance...

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Transcript of Dominance - Loudoun County Public Incomplete Dominance •Codominance. Incomplete Dominance...

  • Dominance

    Relationships

  • Recap

    So

    If you show the dominant phenotype, what could your genotype be?

    What is genotype and phenotype again?

  • If you are unsure if the organism is a pure-

    bred, you can do a Test Cross

    Test Cross: Cross the individual that shows dominant phenotype with a recessive individual

    If offspring 100% dominant

    Original was pure (HD)

    If offspring not 100% dominant

    Original was heterozygous

  • Predicting a Test Cross

  • Remember, Punnett Squares are usually good only for single-gene traits.

    A a

    A

    a Aa

    AA Aa

    aa

    Looking at just one trait is called a MONOHYBRID Cross

  • Looking at TWO traits in one Punnett Square is called a DIHYBRID Cross

  • TRY A DIHYBRID CROSS!

    Show the probabilities of a cross between two people, both heterozygous Full Lips (Ff), Clefted Chin (Cc)!

    F = Full Lips (dominant), f = Thin Lips (recessive)

    C = Cleft Chin (dominant), c = Non-clefted Chin

    The hardest part is segregating the alleles

    Start with FfCc X FfCc Go!

  • FfCc X FfCc

    Ff Cc

    Ff C

    c

    FC

    FC FFCC(full lips, cleft chin)

    Finish Up!

    Fc fC fc

  • Numbers:

    How many Full Lips/Clefted Chins? _____

    How many Thin Lips/Clefted Chins? _____

    How many Full Lips/Non-clefted? _____

    How many Thin Lips/Non-clefted? _____

    So, whats your HomD:Het:Het:HomR ratio?

    ___:___:___:___

    9:3:3:1 -This is the classic ratio for a heterozygous dihybridcross!

    9/16

    3/16

    3/16

    1/16

    9 3 3 1

  • Dominance Relationships

    Complete dominance: one allele shows full dominanceover the other (dominant v. recessive)

    Incomplete dominance: neither allele is fully dominant over the other (mixed phenotype)

    Codominance: Both alleles dominant; one phenotype wins (shows) in some cells, the other shows in other cells (either can show)

  • Which Is This

    Complete Dominance

    Incomplete Dominance

    Codominance

  • Which Is This

    Complete Dominance

    Incomplete Dominance

    Codominance

  • Which Is This

    Complete Dominance

    Incomplete Dominance

    Codominance

    (Though darker colors tend to show more strongly than lighter colors)

    http://creationwiki.org/File:Brown_eyes.jpg

  • Which Is This

    Complete Dominance

    Incomplete Dominance

    Codominance

    http://creationwiki.org/pool/images/c/c6/Codominant.jpg

  • Incomplete Dominance

    In northeast Kansas there is a creature know as a wildcat. It comes in three colors, blue, red, and purple. This trait is controlled by a single gene with incomplete dominance.

    A homozygous (BB) individual is blue, a homozygous (bb) individual is red, and a heterozygous (Bb) individual is purple.

    What would be the genotypes and phenotypes of the offspring if a blue wildcat were crossed with a red one?

    Cross a Purple Cat and a Red cat. Can they have Blue offspring?

    http://www.ksu.edu/biology/pob/genetics/defin.htmhttp://www.ksu.edu/biology/pob/genetics/defin.htmhttp://www.ksu.edu/biology/pob/genetics/defin.htmhttp://www.ksu.edu/biology/pob/genetics/defin.htm

  • Co-Dominance

    Longhorns may be white (CWCW), red (CRCR) or roan (CRCW). Roan longhorns have a mixture of both white hairs and red hairs due to a codominant gene.

    Cross a Roan Bull with a Red Female! What are the genotypes and Phenotypes?

    Can roan cows produce more roan cows?

    http://www.vetmed.ucdavis.edu/cvec/foley_web_site/ef0030_white-cow.jpg