g A variable trait in corn is the presence or absence of knobs at particular sites on some chromosomes. The allele present on each chromosome determines whether or not that chromosome has a knob. Suppose that one member of each of two pairs of homologs in a corn plant has a knob. If this plant is crossed with a knobless plant, what percentage of the offspring is expected to have only knobless chromosomes

Assuming a diallelic gene and complete dominance, the percentage of the offspring that is expected to have only knobless chromosomes is 50%

Available data:

We will assume complete dominance, and that the presence of knobs is the dominant trait.

We will name the dominant allele A, and the recessive allele a.  

Plant 1 seems to be heter0zyg0us for the trait, while plant 2 is h0m0zyg0us.

Cross: Plant 1 with Plant 2

Parentals)  Aa    x    aa

Gametes)  A   a     a     a

Punnett square)     A      a

                       a     Aa     aa

                       a     Aa     aa

F1) 50% of the progeny is expected to be heter0zyg0us, Aa, expressing knobs

     50% of the progeny is expected to be h0m0zyg0us recessive, aa, having knobless chromosomes.

The percentage of the offspring that is expected to have only knobless chromosomes is 50%.

You can learn more about complete dominance at

link

50%

Explanation:

The allele present on each chromosome determines whether or not that chromosome has a knob. Suppose that one member of each of two pairs of homologs in a corn plant has a knob.

This means that on a chromosome with two chromatids, the allele present on one chromatid causes the chromatid to possess knob while the other does not making the plant an heterozygous...

If this plant is crossed with a knobless plant, one whose Chromebook is without knobs, we have

II x II

II - 50% with a knobbed chromatid

II - 50% with only knobless chromosomes.

The first to the left is knobbed, thus the percentage of offspring expected to have only knobless chromosomes would be 50%.