11 3 exploring mendelian genetics
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11-3 Exploring Mendelian Genetics. Key Concepts: What is the principle of independent assortment? What inheritance patterns exist aside from simple dominance? Vocabulary: Independent assortment Incomplete dominance Codominance Multiple alleles Polygenic traits.

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11-3 Exploring Mendelian Genetics

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11 3 exploring mendelian genetics

11-3 Exploring Mendelian Genetics

  • Key Concepts:

    • What is the principle of independent assortment?

    • What inheritance patterns exist aside from simple dominance?

  • Vocabulary:

    • Independent assortment

    • Incomplete dominance

    • Codominance

    • Multiple alleles

    • Polygenic traits


Two factor two gene cross

Two-Factor (Two-Gene) Cross

  • Why is this called a two factor cross?

    Because the experiment tests two characteristics

    controlled by two genes.

  • Mendel’s Experiment: Two-factor cross

    • Mendel crossed two homozygous plants (Pgen)

    • He looked at two genes (seed shape and seed color)

      • Pgeneration: Round&Yellowx Wrinkled &Green

        • F1 offspring produced…?

      • F1 generation: AllRoundYellow peas

  • Which alleles are dominant?

    Round shape and Yellow color.


Summarization mendel s two factor cross

SummarizationMendel’s two factor cross

  • Mendel crossed plants that were homozygous dominant for round yellow peas (RRYY) and plants that were homozygous recessive for wrinkled green peas (rryy).

  • All of the F1 offspring were heterozygous dominant for round yellow peas (RrYy).


In a monohybrid cross

In a monohybrid cross . . .

If the genotype of a plant is Tt, each parent can only pass on one allele per gene in their gametes. (gene = height)

Tt

T ort


For a dihybrid cross

For a dihybrid cross . . .

If the genotype of a plant is TtYy, each parent can STILL only pass on one allele for each gene in their gametes.(gene= height and leaf shape)

TtYy

TY or tY or Ty or ty


Principle of independent assortment

Principle of Independent Assortment

  • States that genes for different traits can segregate independently during the formation of gametes (meiosis).

  • If the genotype of a plant is TtYy (T= gene for height; Y= gene for leaf shape), what are the four possible combinationsof gametes?

  • how do you figure out the gametes?


How do you figure out the possible gametes

How do you figure out the possible gametes?

Remember FOIL (from math???—

the distributive property)

T t Y y

The gametes mom will produce:

F = First

O = Outside

I = Inside

L = Last

Ex: Mom’s genotype

TY, Ty, tY, ty


Independent assortment in other words

Independent Assortment..in other words…

  • Does the segregation of one pair of alleles affect the segregation of another pair of alleles?

    • EX: does the gene that determines seed shape have anything to do with the gene that determines seed color?

  • The answer: NO

  • If genes are not connected, then they should separate (segregate) independently: Independent Assortment


P generation

P generation

F1 generation

  • If you wanted to cross the offspring of the F1 generation…

  • What would the gametes be? (use FOIL)

  • SsYy= SY, sY, Sy, sy

  • SsYy= SY, sY, Sy, sy

  • NEXT—try the cross to get the F2 generation!!!


S s y y x s s y y

SsYy x SsYy

SY SysY sy

SY

Sy

sY

sy


S s y y x s s y y1

SsYy x SsYy

SY SysY sy

SY

Sy

sY

sy


Independent assortment

Independent Assortment

  • The alleles for seed shape segregated independently of the alleles for seed color.

    • This phenomenon is known as…

      • Independent assortment (the 2 genes are on different chromosomes.)


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