In lecture this week, we will discuss alterations of chromosome number or structure that can affect an organism’s phenotype. In many cases, such changes can lead to spontaneous abortion or to a specific genetic defect. This week’s forum article explores the relationship between chromosomal abnormalities and the occurrence of specific genetic disorders. Read the following article DNA Deletion and Duplication and the Associated Genetic Disorders and answer the following questions.

1. What is a chromosomal duplication and why do such duplications adversely affect embryonic development?

2. When does recombination of homologous chromosomes take place? How can duplication events such as that shown in Figure 3 lead to increased genetic diversity and even to the emergence of new species?

3. Explain why low copy repeat (LCR) sequences, like the pericentromeric regions of chromosomes, are often substrates for non-allelic homologous recombination (NAHR). When do such NAHR events lead to inversions and translocations?

4. You are a molecular geneticist. You are attempting to develop a cure for a genetic disorder that results from either a deletion or duplication. Which in your opinion would be the easier of the two conditions to treat? Explain your reasoning.