Question

3. (4 pts). A diploid somatic cell of a hypothetical eukaryote contains two pairs of homologs in its nucleus (2N = 4). One pair of homologs is metacentric and the other pair is submetacentric. The metacentric pair is heterozygous at two gene loci and each locus is on a different arm. At one locus, the alleles are identified by the letters “A” and “a”. At the other locus, the alleles are identified by the letters “B” and “b”. The upper case letter indicates the dominant allele and the lower case indicates the recessive allele at each locus. The dominant alleles of the two gene loci are on one of the metacentric homologs and the recessive alleles are on the other metacentric homolog. The submetacentric homologs are heterozygous for two loci on the long arm. The locus closest to the centromere has alleles symbolized by the letters “E” and “e” while the other locus on the telocentric homologs has alleles represented by the letters “H” and “h” . The dominant alleles of those 2 loci are on one of the telocentric chromosomes while the recessive alleles are on the other homolog.

For the stage of the cell cycle listed below, please draw and label the chromosomes as instructed below and using the allele symbols. Use a vertical line to represent each double-stranded DNA molecule and an open circle, , to indicate the site of the centromere. Clearly label the positions of the centromeres, telomeres, each gene locus and the allele at each gene locus on each chromosome and chromatid. Please do not draw other structures such as the nuclear envelope, spindle fibers etc. Pretend that the chromosomes are sufficiently condensed so that they could be observed as distinct chromosomes. The stage of the cell cycle is: prophase of mitosis (draw the chromosomes that you would expect in one nucleus). Neatly illustrate and label your chromosomes in the box:

Answer 1