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Trihybrid cross
Trihybrid cross

More complex by “easily” calculated
More complex by “easily” calculated
following principles of segregation,
 following principles of segregation,
    independent assortment and
     independent assortment and
              probability
              probability
Trihybrid cross
Trihybrid cross
PUNNETT SQUARE HAS 64
PUNNETT SQUARE HAS 64
BOXES…
BOXES…
DEMONSTRATES THAT
DEMONSTRATES THAT
MENDEL’S PRINCIPLES
MENDEL’S PRINCIPLES
APPLY TO INHERITANCE OF
APPLY TO INHERITANCE OF
MULTIPLE TRAITS
MULTIPLE TRAITS
Trihybrid crosses
Trihybrid crosses
 The basic concepts are the same as with mono- or
 The basic concepts are the same as with mono- or
                  dihybrid crosses
                   dihybrid crosses
                   Just remember:
                    Just remember:
  •• each gamete must have ONE COPY OF EACH
      each gamete must have ONE COPY OF EACH
     GENE
      GENE
  •• random segregation and independent
      random segregation and independent
     assortment still apply
      assortment still apply
Trihybrid crosses
Trihybrid crosses
•• The basic concepts are the same as with mono- or
    The basic concepts are the same as with mono- or
   dihybrid crosses
    dihybrid crosses
•• Just remember:
    Just remember:
    •• each gamete must have ONE COPY OF EACH
        each gamete must have ONE COPY OF EACH
       GENE
        GENE
    •• random segregation and independent assortment
        random segregation and independent assortment
       still apply
        still apply
Trihybrid crosses
Trihybrid crosses

•• tall, pinched pod, axial X dwarf, inflated, terminal
    tall, pinched pod, axial X dwarf, inflated, terminal
••         TT pp AA
           TT pp AA              tt PP aa
                                  tt PP aa
•• F11::
   F          tall, inflated, axial
               tall, inflated, axial
                        Tt Pp Aa

••                    F1 X F1 --> ?
Trihybrid crosses
Trihybrid crosses
•• Step one: Figure out the gametes
   Step one: Figure out the gametes
   produced by each parent (use 2nn))
   produced by each parent (use 2
  •• Parents: Tt Pp Aa; 233 = 8
     Parents: Tt Pp Aa; 2 = 8
  •• eight possible gametes from each parent:
     eight possible gametes from each parent:
     •• TPATPa
        TPATPa      TpA
                    TpA      tPA
                              tPA
        Tpa
        Tpa    tPa
                tPa     tpA
                         tpA      tpa
                                   tpa
Forked-line Method
Forked-line Method

•• Breaks down multi-hybrid crosses into a series
    Breaks down multi-hybrid crosses into a series
   of monohybrid crosses
    of monohybrid crosses
•• Combine the individual ratios (multiply) to get
    Combine the individual ratios (multiply) to get
   the final ratio
    the final ratio
Forked-line Method
Forked-line Method

             Tt Pp Aa X Tt Pp Aa
              Tt Pp Aa X Tt Pp Aa
     Break into Tt X Tt; Pp X Pp; Aa X Aa
     Break into Tt X Tt; Pp X Pp; Aa X Aa

••   Tt X
     Tt X   Tt --> 3/4 T: 1/4 tt
             Tt --> 3/4 T: 1/4
••   Pp X
     Pp X   Pp --> 3/4 P: 1/4 p
            Pp --> 3/4 P: 1/4 p
••   Aa X
     Aa X   Aa --> 3/4 A: 1/4 a
            Aa --> 3/4 A: 1/4 a
Forked line
Forked line
FF offspring:
 2 offspring:                   3/4 A   --> 27/64 TPA
  2

                    3/4 P
                            <   1/4 a   --> 9 /64 TPa
      3/4 T
                <   1/4 p
                                3/4 A

                                1/4 a
                                        --> 9 /64 TpA

                                        --> 3 /64 Tpa

                                3/4 A   --> 9 /64 tPA
                    3/4 P
                            <   1/4 a   --> 3 /64 tPa
      1/4 t
                <               3/4 A   --> 3 /64 tpA
                    1/4 p
                            <   1/4 a   --> 1 /64 tpa
Forked-line
Forked-line


••   Can find genotypic ratios
      Can find genotypic ratios
••   substitute 1/4 TT; 1/2 Tt; 1/4 tt, etc.
      substitute 1/4 TT; 1/2 Tt; 1/4 tt, etc.
••   Can go straight to one phenotype or genotype
      Can go straight to one phenotype or genotype
••   ignore all branches except those leading to the desired
      ignore all branches except those leading to the desired
     phenotype or genotype
      phenotype or genotype
Trihybrid
Trihybrid
Cross
Cross
The Principle of Independent
The Principle of Independent
Assortment
Assortment
•• Factors for different
    Factors for different
   traits assort
    traits assort
   independently of one
    independently of one
   another
    another
  •• Genes are inherited
      Genes are inherited
     independently of each
      independently of each
     other
      other
  •• Segregate randomly in
      Segregate randomly in
     gametes
      gametes
•• Dihybrid Cross
   Dihybrid Cross
Genetic trihybrid cross
Branch Diagram of Dihybrid Cross
Branch Diagram of Dihybrid Cross
P
h
e
n
o
t
y
p
e
Genotype vs.
Genotype vs.
Phenotype
Phenotype

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Genetic trihybrid cross

  • 1. Trihybrid cross Trihybrid cross More complex by “easily” calculated More complex by “easily” calculated following principles of segregation, following principles of segregation, independent assortment and independent assortment and probability probability
  • 2. Trihybrid cross Trihybrid cross PUNNETT SQUARE HAS 64 PUNNETT SQUARE HAS 64 BOXES… BOXES… DEMONSTRATES THAT DEMONSTRATES THAT MENDEL’S PRINCIPLES MENDEL’S PRINCIPLES APPLY TO INHERITANCE OF APPLY TO INHERITANCE OF MULTIPLE TRAITS MULTIPLE TRAITS
  • 3. Trihybrid crosses Trihybrid crosses The basic concepts are the same as with mono- or The basic concepts are the same as with mono- or dihybrid crosses dihybrid crosses Just remember: Just remember: •• each gamete must have ONE COPY OF EACH each gamete must have ONE COPY OF EACH GENE GENE •• random segregation and independent random segregation and independent assortment still apply assortment still apply
  • 4. Trihybrid crosses Trihybrid crosses •• The basic concepts are the same as with mono- or The basic concepts are the same as with mono- or dihybrid crosses dihybrid crosses •• Just remember: Just remember: •• each gamete must have ONE COPY OF EACH each gamete must have ONE COPY OF EACH GENE GENE •• random segregation and independent assortment random segregation and independent assortment still apply still apply
  • 5. Trihybrid crosses Trihybrid crosses •• tall, pinched pod, axial X dwarf, inflated, terminal tall, pinched pod, axial X dwarf, inflated, terminal •• TT pp AA TT pp AA tt PP aa tt PP aa •• F11:: F tall, inflated, axial tall, inflated, axial Tt Pp Aa •• F1 X F1 --> ?
  • 6. Trihybrid crosses Trihybrid crosses •• Step one: Figure out the gametes Step one: Figure out the gametes produced by each parent (use 2nn)) produced by each parent (use 2 •• Parents: Tt Pp Aa; 233 = 8 Parents: Tt Pp Aa; 2 = 8 •• eight possible gametes from each parent: eight possible gametes from each parent: •• TPATPa TPATPa TpA TpA tPA tPA Tpa Tpa tPa tPa tpA tpA tpa tpa
  • 7. Forked-line Method Forked-line Method •• Breaks down multi-hybrid crosses into a series Breaks down multi-hybrid crosses into a series of monohybrid crosses of monohybrid crosses •• Combine the individual ratios (multiply) to get Combine the individual ratios (multiply) to get the final ratio the final ratio
  • 8. Forked-line Method Forked-line Method Tt Pp Aa X Tt Pp Aa Tt Pp Aa X Tt Pp Aa Break into Tt X Tt; Pp X Pp; Aa X Aa Break into Tt X Tt; Pp X Pp; Aa X Aa •• Tt X Tt X Tt --> 3/4 T: 1/4 tt Tt --> 3/4 T: 1/4 •• Pp X Pp X Pp --> 3/4 P: 1/4 p Pp --> 3/4 P: 1/4 p •• Aa X Aa X Aa --> 3/4 A: 1/4 a Aa --> 3/4 A: 1/4 a
  • 9. Forked line Forked line FF offspring: 2 offspring: 3/4 A --> 27/64 TPA 2 3/4 P < 1/4 a --> 9 /64 TPa 3/4 T < 1/4 p 3/4 A 1/4 a --> 9 /64 TpA --> 3 /64 Tpa 3/4 A --> 9 /64 tPA 3/4 P < 1/4 a --> 3 /64 tPa 1/4 t < 3/4 A --> 3 /64 tpA 1/4 p < 1/4 a --> 1 /64 tpa
  • 10. Forked-line Forked-line •• Can find genotypic ratios Can find genotypic ratios •• substitute 1/4 TT; 1/2 Tt; 1/4 tt, etc. substitute 1/4 TT; 1/2 Tt; 1/4 tt, etc. •• Can go straight to one phenotype or genotype Can go straight to one phenotype or genotype •• ignore all branches except those leading to the desired ignore all branches except those leading to the desired phenotype or genotype phenotype or genotype
  • 12. The Principle of Independent The Principle of Independent Assortment Assortment •• Factors for different Factors for different traits assort traits assort independently of one independently of one another another •• Genes are inherited Genes are inherited independently of each independently of each other other •• Segregate randomly in Segregate randomly in gametes gametes •• Dihybrid Cross Dihybrid Cross
  • 14. Branch Diagram of Dihybrid Cross Branch Diagram of Dihybrid Cross P h e n o t y p e