A cell has two pairs of submetacentric chromosomes, which we will call chromosomes Ia, Ib, IIa, and IIb (chromosomes Ia and Ib are homologs, and chromosomes IIa and IIb are homologs). Allele M is located on the long arm of chromosome Ia, and allele m is located at the same position on chromosome Ib. Allele P is located on the short arm of chromosome Ia, and allele p is located at the same position on chromosome Ib. Allele R is located on chromosome IIa and allele r is located at the same position on chromosome IIb.a. Draw these chromosomes, identifying genes M, m, P, p, R, and r, as they might appear in metaphase I of meiosis. Assume that there is no crossing over.b. Taking into consideration the random separation of chromosomes in anaphase I, draw the chromosomes (with genes identified) present in all possible types of gametes that might result from this cell’s undergoing meiosis. Assume that there is no crossing over.

The dog Canis familiaris is a diploid organism with 39 pairs of homologous chromosomes. What is the 2n number for the dog?  What is the n number for the dog?

What types of chromosome mutations are required to change this chromosome into the following chromosomes? (In some cases, more than one chromosome mutation may be required.) Q. A B • C F E D G

Two different genes are located on the same chromosome in rabbits. A particular female rabbit is heterozygous for alleles of both genes, with alleles arranged as shown in the diagram to the right. Scientists know that the two genes are on the same chromosome, but do not know their exact relative positions, as indicated by the dashed line. Suppose this female mates with a male rabbit in which the same r. chromosome pair looks like this: Which of the following statements best describes the likelihood that this pair of rabbits would have offspring with a chromosome pair that looks like this: * O More likely if the two genes are not very close together on the chromosome E-i-e R- O Not likely, because the R and e alleles are not on the same chromosome in either parent O More likely if the two genes are very close together on the chromosome O Very likely, because the random assortment of chromosomes during cell division to make sperm or eggs allows for the mixing of all alleles