Molecular Biology BIO 250

Genetics BIO 203 Test 4 Guide Nov 30

Test 4 – Chapters 10 (including parts of 11), 22, 23 & Epigenetics

Types of Questions: Multiple-choice, matching, short answer, fill in the blanks, explain, work out problems, label the diagrams.

Chapter 10 DNA Replication & Synthesis  What is meant by DNA replication and when does it occur in the eukaryotic cell cycle?  What are the three possible hypotheses for DNA replication and which one is actually taking place in the cell.  Skip Messelson –Stahl experiment and Taylor-Woods-Hughs experiment  Origin of replication and bi-directional replication. How many origins/replicons are present in E. coli chromosome?  Learn how DNA is synthesized in bacteria. What does dNTP stands for? What are the building blocks for DNA synthesis?  What are the properties of bacterial DNA polymerases? (table 10.2) Learn the functions of DNA polymerase I, II and III. Which ones have 3’-5’ exonuclease activity? 5’-3’ exonuclease activity?  Learn the mechanism DNA replication. Synthesis of leading strand & lagging strand, priming of DNA synthesis, Okazaki fragments  Why lagging strand cannot be synthesized continuously?  What are the enzymes and other proteins assisting in DNA replication? Learn the role played by each one of these.  How does Proofreading work?  Multiple origins of replication in eukaryotes. Why are multiple origins necessary in eukaryotes?  Why do ends of linear eukaryotic chromosomes pose problems during replication of ends? Why do telomeres become shorter after each cell division?

Chapter 22 Quantitative Genetics  What are quantitative traits and how are these different from Qualitative traits?  Give examples of quantitative traits in animals, plants and humans.  Can the inheritance of a quantitative t rat be explained in Mendelian terms?  What are additive alleles and non additive alleles?  What is the distribution of a quantitative trait look like?  What are the two statistics that are used to characterize a quantitative trait? (Mean & Variance). Be able to calculate these from a small data set.  What is meant by heritability? How do you calculate the broad-sense heritability?  What are QTL’s? Give an example from tomato. Can these be mapped?

Chapter 23 Population Genetics

 Know what is meant by allele frequency, genotype frequency.  What are the assumptions that pertain to a population in a Hardy-Weinberg equilibrium. Be able to describe these assumptions.  What are the two laws of Hardy-Weinberg equilibrium that apply under the above assumptions?  Be able to calculate allele frequencies in a population in Hardy-Weinberg equilibrium.  What are the forces that change allele frequency in populations? Which one has the most effect?  Give some examples of natural selection and explain how it works.  What is meant by hybrid vigor? Inbreeding depression?

Epigenetics (Covered in the video Ghost in your genes)

 What is epigenetics? How does this differ from other fields of genetics  What are the three main mechanisms of epigenetic control of gene expression?  What is meant by genetic imprinting?  Learn the symptoms and causes of the two syndromes caused by genetic imprinting, Angleman and Prader-Willi. Which one is caused by a deletion in the chromosome 15 in sperm? Which one in egg? How can you explain these two syndromes in the light of epigenetics?  How does epigenetics influence susceptibility to cancer? Which genes might be silenced that would lead to cancer?

Sample questions:

1. Which of the following terms accurately describes the replication of DNA? A. conservative B. dispersive C. semicontinuous D. liberal E. semiconservative

2. The discipline within genetics that studies changes in allele frequencies is known as A. population genetics. B. transmission genetics. C. cytogenetics D. molecular genetics. E. none of the above.

Problems/Short answer/etc:

3. DNA replication: Draw a diagram of a replication fork. Label the 5’ and 3’ ends of all DNA strands, original and newly synthesized. In addition identify the following on the diagram.

Leading strand, lagging strand, Okazaki fragments, enzyme that deals with the supercoils (DNA gyrase), enzyme that unwinds (helicase) and denatures the double helix, SSBPs, enzyme that synthesizes an RNA primer to provide a free 3 OH group (primase), enzyme that synthesizes new DNA (DNA polymerase III), enzyme that removes RNA primers (DNA polymerase I),, Enzyme that glues the pieces of the lagging strand together (DNA ligase).

4. Human blood types, MM, MN and NN are controlled by two alleles (M & N) of a single gene. In a population of 100 individuals, 49% are of the NN blood type. What percentage is expected to be MN assuming Hardy-Weinberg equilibrium conditions?

5. Write three components of phenotypic variance (Vp).

6. Define broad sense heritability (H2). Interpret the value of H2 approaching 1.0.