1. State the three Principles of Mendel described to explain hereditary mechanisms. Also state one exception for each of the Principles.
2. Explain why genetic and physical maps of chromosomes are colinear.
3. If a is linked to b, and b to c, and c to d, does it follow that a recombination experiment would detect linkage between a and d? Explain.
4. In this question, assume that a set of 22 autosomal chromosomes has 20000 genes, X chromosome has 2000 genes and Y chromosome has 100 genes. We define 'relatedness' between two individuals (which are two gene sets) as:
relatedness = the number of genes in the intersection of two gene sets/the number of genes in the union of two gene sets
a) Calculate the relatedness between a mother and her son.
b) Calculate the relatedness between a mother and her daughter.
c) Calculate the relatedness between a father and his son.
d) Calculate the relatedness between a father and his daughter.
5. Spontaneous mutations can occur due to tautomeric shifts of bases. Describe this phenomenon and give one example of how a tautomeric shift can introduce a mutation.
6. (a) What are the genotypic differences between F- cells, F+ cells, and Hfr cells? (b) What are the phenotypic differences? (c) By what mechanism are F- cells converted to F+ cells? F+ cells to Hfr cells? Hfr cells to F+ cells?
7. Answer three of the following five questions about transposons.
a) What distinguishes IS and Tn3 elements in bacteria?
b) A researcher has found a new Tn5 element with the structure IS50L strr bler kanr IS50L. What is the most likely origin of this element?
c) What is the medical significance of bacterial transposons?
d) Explain how cut-paste transposons can increase their copy number (hence, replicate) in genomes.
e) Antibiotic resistance gene carrying plasmids can be transmitted between different bacterial species. Explain the evolution of plasmids from transposable elements.
8. In order to achieve genetic balance, organisms change the activity of their sex chromosomes. Give three mechanistic explanations on how this is achieved. Imagine that you are studying a new cell type. Suggest a set of experiments you would conduct to find out which of these mechanistic explanations is compatible with this cell type.
9. Explain why some tetraploids are fertile while some are sterile.
10. Genes a and b are 20 cM apart. An a+ b+/a+ b+ individual was mated with an a b/a b individual.
(a) Diagram the cross and show the gametes produced by each parent and the genotype of the F1.
(b) What gametes can the F1 produce, and in what proportions?
(c) If the F1 was crossed to a b/a b individuals, what offspring would be expected, and in what proportions?
(d) Is this an example of the coupling or repulsion linkage phase?
(e) If the F1 were intercrossed, what offspring would be expected and in what proportions?