Gen.Class+notes_4

Gen.Class+notes_4 - Mendel also look at di-hybrid crosses:...

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Mendel also look at di -hybrid crosses: peas that differ in two characteristics. Such as peas that differ in both shape and color. These crosses examine the rules of inheritance of two traits located at different locus.
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The parents are homozygous for both traits. Segregation produces only one kind of allele for each trait: RRYY gives RY
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Alleles at each locus separate independently and when forming the gametes they are assorted independently of each other. R r Y y R Y R y r Y r y We end up with all four permutations present in equal proportions.
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RrYy RrYy
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R_ Y_ = 9 round and yellow
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R_ Y_ = 9 round and yellow R_ yy = 3 round and green
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R_ Y_ = 9 round and yellow R_ yy = 3 round and green rr Y_ = 3 wrinkled and yellow
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R_ Y_ = 9 round and yellow R_ yy = 3 round and green rr Y_ = 3 wrinkled and yellow rr yy = 1 wrinkled and green
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R_ Y_ = 9 round and yellow R_ yy = 3 round and green rr Y_ = 3 wrinkled and yellow rr yy = 1 wrinkled and green This is consistent with the monohybrid phenotypic ratios : R_ Y_ = 9 round and yellow R_ yy = 3 round and green rr Y_ = 3 wrinkled and yellow rr yy = 1 wrinkled and green R_ : rr 9 + 3 : 3 + 1 12 : 4 3 : 1 Y_ : yy 9 + 3 : 3 + 1 12 : 4 3 : 1 These results suggested to Mendel that two traits in a dihybrid cross assort independently form each other. We can treat them separately in order to find ratios.
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Conclusions: The alleles encoding color separated independently from the alleles encoding shape: Law of independent assortment . This is only true if the traits (genes) under consideration are in different chromosomes or very far apart in the same chromosome. When calculating ratios we can analyze each trait separately. The Punnet square is useful but a easier and faster way is to use branch diagrams.
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Interphase: S phase (DNA synthesis) allele segregation allele segregatio n Remember that the Law of segregation states that two alleles (two forms of gene R) at the same loci separate independently of each other during gamete formation.
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The law of independent assortment states that when these two alleles (two forms of gene R in I) separate, they do so independently of the separation of alleles ( two forms of gene B in III) at other loci .
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The Law of independent assortment states: “ the inheritance of alleles at different locus separate independently of each other” . Remember that the Law of segregation states that two alleles (two forms of gene R) at the same loci separate independently of each other during gamete formation. The law of independent assortment states that when these two alleles (two forms of gene R) separate, they do so independently of the separation of alleles ( two forms of gene B) at other loci .
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phenotypic ratios for the cross of a heterozygous and a homozygous (backcross): Remembe r: when crossing a heterozygous and a
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This note was uploaded on 02/09/2012 for the course GENETICS 380 taught by Professor Glodowski during the Spring '08 term at Rutgers.

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Gen.Class+notes_4 - Mendel also look at di-hybrid crosses:...

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