Jump to... Wild-type porcupines have po porcupine that lack quills, giving them

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Jump to... Wild-type porcupines have po porcupine that lack quills, giving them a "cuddly porcupine results in all wild-type offspring. The results of crosses between some of the true-breeding nty quills. Scientists have identified several true-breeding strains of Map e. Crossing any cuddly mutant to a wild-type cuddly strains are as follows: cud1x ad2 = all cuddly offspring cud2 x cud3-all pointy offspring Why did the offspring from the cross between cud2 x cud3 mutants show the wildtype phenotype? O complementation O codominance O incomplete dominance Which two mutations affect the same gene? cud1 cud2 cud3 Continued below What is the expected result of a cross between cud1 and cud3? O Previous God Up & View Scano Check Answer Next Exit

Explanation / Answer

1. Cuddly is the mutation in porcupines that results in tails that lack quills. All pointy offsprings were obtained when cud2 was bred with cud3. Cud2 and cud 3 are present in different genes. When the mutations are in separate genes, cud2 strain has mutation in cud2 while maintaining a normal copy of Cud 3. Similarly, cud3 strain has mutation in Cud 3 while maintaining a normal copy of cud2. When these two strains breed, the F1 progeny will either expresses the mutant allele of cud2 and the wild type allele of Cud3. The F1 can also express the wild type allele for cud2 and the mutant allele for cud3. Since the progenies express one functional wild type allele, the wild type phenotype of pointy is observed in this cross.

However, if the two alleles were in the same gene, the F1 progeny would have inherited one mutant copy of both cud2 and cud3, while maintainingI a wild type allele of both genes. Hence, the F1 offspring would have had the cuddly mutation and will be cuddly. This does not happen in cud2Xcud3 cross.

This is what happens in cud1Xcud2 cross, which are present in the same gene. All pointy offprings were ovbserved in this cross. Hence, cud1 and cud2 mutations are present on same gene.

As the test, allows to identify whether the two allele are of the same gene or belong to different gene, this test is the complementation test.

Right option is complementation.

2. Cud1 and cud2 mutations affect the same gene, as their cross offsprings have cuddly tails (mutant phenotype). The offspring will inherit one mutant allele of both cud1 and cud2 and one wild type allele of both cud1 and cud2. Hence, a mutant phenotype will be seen.

Right option is cud1 and cud2.

3. Cud1 and cud 2 are present on the same gene. Cud2 and cud3 are present on different genes. Hence, cud1 and cud3 will also be present on different genes. A cross between the cud1 and cud3 will result in the wild type pointy phenotype, as the offspring will inherit one wild type allele of the two genes.

Right option:

Cuddly offspring = 0%

Pointy offspring= 100%

4. Both cud2 and cud 3 are present on different genes. Consider the dominant allele in cud mutation to be C and recessive to be c. Hence, genotype of cud2 X cud3 offspring will be C2c2C3c3. One allele is wildtype and the second is mutant, giving rise to a pointy phenotype. Punnett square of the cross between two such pointy offspring is:

Parent 1

C2c2C3c3

C2C3

C2c3

c2C3

c2c3

Parent 2

C2c2C3c3

C2C3

C2C2C3C3

Pointy

C2C2C3c3

Pointy

C2c2C3C3

Cuddly

C2c2C3c3

Pointy

C2c3

C2C2C3c3

Pointy

C2C2c3c3

Cuddly

C2c2C3c3

Pointy

C2c2c3c3

Cuddly

c2C3

C2c2C3C3

Pointy

C2c2C3c3

Pointy

C2c2C3C3

Pointy

c2c2C3c3

Cuddly

c2c3

C2c2C3c3

Pointy

C2c2c3c3

Cuddly

c2c2C3c3

Cuddly

c2c2c3c3

Cuddly

Inheriting either the recessive c2 and/or c3 will give a mutant phenotype.

There are 9 pointy and 7 cuddly offsprings.

Right option is 9 pointy: 7 cuddly

Parent 1

C2c2C3c3

C2C3

C2c3

c2C3

c2c3

Parent 2

C2c2C3c3

C2C3

C2C2C3C3

Pointy

C2C2C3c3

Pointy

C2c2C3C3

Cuddly

C2c2C3c3

Pointy

C2c3

C2C2C3c3

Pointy

C2C2c3c3

Cuddly

C2c2C3c3

Pointy

C2c2c3c3

Cuddly

c2C3

C2c2C3C3

Pointy

C2c2C3c3

Pointy

C2c2C3C3

Pointy

c2c2C3c3

Cuddly

c2c3

C2c2C3c3

Pointy

C2c2c3c3

Cuddly

c2c2C3c3

Cuddly

c2c2c3c3

Cuddly

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