Fur length is coded by a diallelic gene expressing complete dominance. The parents of the ff hamster might be either Ff and Ff (test 2) or ff and ff (test 3).
According to the provided data, there is a single diallelic gene involved in the expression of the trait fur length. And this gene seems to express complete dominance.
We talk about complete dominance when the dominant allele completely masks the recessive allele. It is an inheritance pattern.
This is the case of individuals that are heter0zyg0us for a particular gene and express the dominant trait. The dominant allele is hiding the expression of the recessive allele. Many genes show complete dominance.
In the exposed example,
Let us assume that he mystery hamster has long fur, meaning that its genotype is ff because this is the recessive phenotype.
We need to find out which are the parents of this hamster.
Note: This explanation will be done according to the previously mentioned genotype and phenotype proposed for the mystery hamster. You should check if this information matches your problem statements.
Test One
Cross: FF x F-
(The symbol - represents either a recessive or dominant allele)
F1) 100% of the progeny is expected to carry at least one dominant allele, expressing only the dominant phenotype short fur.
Phenotype ratio ⇒ 4: 0
short fur: long fur
Since there are no long-furred animals among the offspring, these are not the mystery hamster parents.
Test Two
Cross: Ff x Ff
F1)
25% = 1/4 of the progeny is expected to be ff expressing long fur
25% = 1/4 of the progeny is expected to be FF expressing short-fur
50% = 1/2 of the progeny is expected to be Ff expressing short-fur
Phenotype ratio ⇒ 3: 1
short fur: long fur
From this cross it is expected to get 25% long-furred animals, so these could be the parents of the mystery hamster.
Test Three
Cross: ff x ff
F1) 100% of the progeny is expected to be ff expressing long fur
Phenotype ratio ⇒ 0:1
short fur: long fur
From this cross we expected to see only long-furred animals, so these could also be the parents of the mystery hamster.
According to the genotype and phenotype proposed for the mystery hamster -ff-, the possible parents of this animal might be the ones of tests two and three.
Tests Possible parents
Test 2 Ff x Ff
Test 3 ff x ff
Please remember to check this information with the one in your exercise.
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