Question

When Mendel crossed a true-breeding purple-flowered pea plant with a true-breeding white-flowered pea plant, he observed that all of the F1 offspring had purple flowers. When these F1 plants were selfed, he found 3/4 were purple and 1/4 were white. Which of the following observations supports Mendel's conclusion that each progeny can carry two alternative copies of a "factor"When the white progeny are selfed, only white progeny result.When the purple progeny are crossed with the white progeny, only purple progeny result.When the purple progeny are selfed, only purple progeny result.When the purple progeny are selfed, both white and purple progeny result.

Answer 1

Answer:

When the purple progeny are selfed, both white and purple progeny result.

Explanation:

Mendel performed a monohybrid cross i.e. one which involves a single gene or character. This gene which Mendel called factor codes for flower colour in peas. After crossing the pea that produced purple flowers only i.e. homozygous (PP) with one that produces white flowers only i.e. homozygous (pp), he obtained a F1 offspring that has all purple flowers.

This observation led him to his law of dominance, where he stated that an allele is capable of masking the expression of another allele in the heterozygous. Mendel called the allele that masks the DOMINANT allele while the allele being masked, RECESSIVE allele. He then self-crossed the purple F1 offsprings to produce a F2 offsprings with a 3Purple: 1White phenotypic ratio.

This observation led him to propose the law of segregation, which states that the alleles of a gene will separate into gametes during gamete formation. Hence, this showed that the alleles for white colour of flower were present in the F1 offsprings but were phenotypically masked. They were later expressed in the F2 offsprings.

In a nutshell, the F1 offsprings produced were in a heterozygous state i.e combination of alternative forms of alleles (Pp). This alleles were separated into gametes during meiosis. This supports Mendel's conclusion that each F1 progeny contains two alternative forms of the flower colour gene.