Dihybrid Cross

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Anonymous
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129951
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Dihybrid Cross
Updated:
2012-01-23 11:36:53
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Dihybrid cross biology
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Description:
Higher Biology - Unit Two - Dihybrid Cross
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  1. What is a dihybrid cross?
    A cross between two homozygous parents who differ in two characteristics ie two genes are being studied in the same breeding experiment
  2. In the dihybrid cross, the offspring with the same phenotype of the original parents are called...?
    parentals
  3. In the dihybrid cross, the offspring with different combinations of the parental phenotype are called...?
    recombinants
  4. What is a dihybrid backcross (testcross)?
    It involves crossing the heterozygous hybrid with a double recessive. It allows us to test whether genes are linked or unlinked
  5. When genes are on the same chromosome and their alleles are transmitted together, they are said to be...?
    linked
  6. What is the phenotypic ratio of the F2 generation from an unlinked F1 x F1 cross?
    9 : 3 : 3 : 1
  7. What is the phenotypic ratio of the F2 generation from an unlinked F1 backcross?
    1 : 1 : 1 : 1
  8. What is the phenotypic ratio of the F2 generation from a linked F1 cross?
    3 : 1
  9. What is the phenotypic ratio of the F2 generation from a linked F1 backcross?
    1 : 1
  10. If two genes are completely linked then a backcross would not produce any F2 recombinants. However, when backcrosses are carried out the F2 may be found to contain some recombinants. How can this be explained?
    Crossing over
  11. The seperation of linked genes and the new combinations of alleles is an important source of...?
    variation
  12. Where can chiasmata occur?
    At any point along a chromosome
  13. More crossing over can occur between two genes that are _______ ________ from each other than two that are ________ _______?
    • farther away
    • close together
  14. What is the percentage number of the F2 recombinants called?
    Recombination frequency (RF) or Cross-over Value (COV)
  15. The higher the RF or COV the _______ ________ the genes are on the chromosome?
    further apart
  16. What can be used to map genes?
    COV

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