Question

The allele "D" would be cleaved three times by EcoRI, resulting 4 fragments: 839, 262, and 215 bp, 151 bp. The allele with the “d” would be cleaved twice by EcoRI, resulting in 3 fragments: 753 bp, 512 bp, 202 bp.

a) If a plant has a genotype of DD, and the sample was digested with EcoRI. How many fragments do you have? And How many bands do you see on the gel electrophoresis for this sample?

b) If a plant has a genotype of Dd, and the sample was digested with EcoRI. How many fragments do you have? And how many bands do you see on the gel electrophoresis for this sample?

c) If a plant has a genotype of dd, and the sample was not digested. How many fragments do you have? And how many bands do you see on the gel electrophoresis for this sample?

d) If a plant has a genotype of Dd, and the sample was not digested. How many fragments do you have? And how many bands do you see on the gel electrophoresis for this sample?

Answer 1

a). Answer:

Since the plant is homozygous having genotype for the allele DD, thus the sequence of both the homologus alleles will be the same. When the two alleles are digested by EcoRI, the number of fragments will be eight four from each allele.

Now when gel electrophoresis is carried out, there will be only four bands. The reason is that the two alleles being similar will give rise to fragments of similar sizes. The fragments having similar size will move the same distance in the gel under the electric field and will form the single band. As there are four types of fragments according to size and each type has two fragments. Thus eight fragments will form four bands.

The band which contains the fragments of largest size will be closest to the the negative electrode and the smallest will be farthest from the negative electrode.

b).

Since the two alleles are different and one gives four fragments and other gives three fragments and all the fragments differ in size. Keeping in mind the above explanation, there will be seven fragments and seven bands.

c).

Since the two alleles are not digested and are of similar size of 1467 bp. There will be two fragments and one band.

d).

Since there are two alleles thus there will be two fragments, but the size of the two fragments is same though they differ in sequence a little they will form a single band on electrolysis.