Question

Label all chromosomes with specific alleles of the marker, using D¹for the allele detected by the lower band and D²for the allele detected by the upper band on the gel, so that they have a genotype that would produce the gel shown.  

I'm no quite getting what corresponds with the D1/D2 labels.

Part II. *** Below is an image of a gel showing the results of genotyping a Father (actual father), Child, and Mother for a single DNA marker. Below that is a diagram representing the chromosomes of these same individuals. The position of the DNA marker on the chromosome is indicated by the horizontal dash. Label all chromosomes with specific alleles of the marker, using D' for the allele detected by the lower band and D² for the allele detected by the upper band on the gel, so that they have a genotype that would produce the gel shown. Father Child Mother Father Mother X Child

Answer 1

Every gene or DNA marker will have one pair of alleles associated with it. These alleles are being labeled as D1/D2 here. In the genotyping result, parents have two bands while the child shows only one thicker band.

So, from this information, you have to deduce which alleles have been passed on to the child by each of the parents. From the gel image, you should be able to tell which allele-either D1 or D2 is present in the child.