Question

If the frequency of parental from is figure than 25% in a dihybrid test cross, what does it indicate about the two genes involved The egg of On animal contains 10 chromosomes, of which one is X chromosome.

How many outcomes would these be in the karyotype of the animal?

Answer 1

• Dihybrid cross is where individuals that differed in 2 characters are crossed.
• Usually, the Law of independent assortment is followed where both the traits are independently inherited by the progeny.
• But in case of Linkage where the alleles for 2 different traits are present on the same chromosome. Due to the linkage, the traits are not inherited independently and parental characters are retained in the majority of the progeny.
• In case of recombinants where the alleles are present on the same chromosome but at the time of crossing over during meiosis, the alleles might be exchanged between the sister chromatids. Where there are 50-50 chances for both parental and non-parental characters to be shown in the progeny.
• If 25% is the frequency of the parental character shown in the progeny in the dihybrid cross that means that the alleles are not present on the same chromosome and are assorted independently at the time of gamete formation.

• The egg of an animal contains 10 chromosomes. The egg is a gamete formed in the female body.
• Gametes usually are formed by the process of meiosis where the genetic material is halved at the end of the division. Therefore the individual cell before the gamete/egg formation has 20 chromosomes where there are 9 pairs of autosomes and I pair of sex chromosome (which determines the sex of organism)
• The gamete formed by this individual has 10 chromosomes where there are 9 autosomes and 1 X chromosome.