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WWU BIOL 321 - Final Exam Info/Data Sheet

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1 Biol 321 Spring 2011 Final Exam Info/Data Sheet NAME______________________ You MUST RETURN this sheet with your Exam Section 1 Problem 7 Autosomal Recessive 1. trait appears in progeny of unaffected parents 2. the trait breeds true and both sexes are equally affected 3. some degree of inbreeding may be present (rare trait) Autosomal Dominant 1. affected offspring have at least one affected parent 2. trait is passed directly from affected individual to affected individual 3. two affected individuals may have an unaffected child (that is, the trait may not breed true) 4. both sexes are equally affected X-linked Recessive 1. all daughters of affected males are carriers; all sons of affected females are affected 2. the phenotype is not transmitted from father to son but rather from father to grandson 3. phenotypic expression is higher in males than in females 4. affected female will have an affected father X-linked Dominant 1. affected males produce all affected daughters and no affected sons 2. a heterozygous female will transmit the trait to about 1/2 of her sons and about 1/2 of her daughters2 Section 1 Problem 93 Section 1 Problem 8 Haplotypes are shown for both families for the same nine STR markers on autosome 8. Unaffected siblings from family 1 have been omitted.4 Section 2 Option 1 Prader-Willi syndrome (PWS) is characterized by short stature, obesity and mental retardation. This trait is usually caused by a deletion (of a chunk of the chromosome) on the paternally derived copy of chromosome 15. Deletions of the same region of the maternal chromosome do not cause PWS since the corresponding region in the maternally derived chromosome is normally inactivated during oogenesis by a process known as genomic imprinting which prevents transcription of specific genes in this region. An individual heterozygous for a normal maternal copy of chromosome 15 and a paternal chromosome 15 with a deletion will have PWS since there will be no transcription of the PWS-related gene. In the family shown below, neither parent has PWS (which shows complete penetrance). [In contrast to the usual type of PWS mutation, the father in this family does not have a deletion on either copy of chromosome 15 (data not shown)]. The agarose gel shows an STR polymorphism that has been tracked using PCR and is linked to the region of chromsome 15 associated with PWS. STR polymorphisms on other autosomes confirm that individual #3 is the father of #2. 1 2 3 4 5 The lane numbers on the agarose gel correspond to the the symbol numbers on the pedigree. Note that this analysis is equivalent to a DNA fingerprinting gel and does not involve any restriction digest of the PCR products. Larger PCR products  Smaller PCR products5 SECTION 2: OPTION 2 Published online 13 September 2007 | Nature | doi:10.1038/news070910-10 Heidi Ledford Knocking out a single gene nearly doubles the lifespan of mice with the animal model of Lou Gehrig's disease, suggesting that the gene may one day become a target for therapies in humans. Lou Gehrig's disease, otherwise known as amyotrophic lateral sclerosis (ALS), is a neurodegenerative disease that gradually erodes motor control. Death usually follows within three to five years of diagnosis. There is no cure, and the only drug available that slows progression of the disease, riluzole, prolongs survival only by a few months. Mice develop ALS-like symptoms when they have a mutation in a gene called SOD1 (superoxide dismutase)— a mutation that causes about 1-2% of human ALS cases. The enzyme produced by the wildtype copy of this gene is responsible for destroying free superoxide radical in the body and research using these animal models has suggested that chemically reactive forms of oxygen that can damage cells contribute to the disease. Several proteins present in the bodies of mice and people are known to generate reactive oxygen species as part of their normal function in cell signalling and inflammation. So John Engelhardt and his colleagues at the University of Iowa in Iowa City decided to look closely at two of these — Nox1 and Nox2 — to see whether turning down the amount of such proteins could slow the progression of ALS symptoms. It did — dramatically. The team found that ALS mice lacking both copies of the gene that specifies Nox2 produced fewer reactive oxygen species and lived on average for 229 days — 97 days longer than those who had normal levels of Nox21. The study also shows that even a 50 percent reduction in Nox2 activity can significantly delay the onset of motor neuron disease. In an unexpected twist, many of the mice that lacked Nox2 also suffered from aggressive eye infections that, if left untreated, were often fatal. The reason for this is not known. Double whammy Eliminating the gene for Nox1 also extended lifespan, but only by 33 days. These results are still exciting, says neurologist Serge Przedborski of Columbia University in New York, because Nox1 is expressed, in part, in blood vessels, and there are hints that something might be going on in these vessels that affects the disease. Work published last year by Przedborski also showed that eliminating Nox2 prolongs life in ALS mice, but the effect found in that research was much smaller: the mice only survived an additional 13 days2. Differences between the two results could stem from the different genetic backgrounds of the mice used, says Engelhardt.6 Section 3 Option 1 Essay Choice A Risk = contributes to addictive personality Each risk allele is presented as a puzzle piece of a different color or shape. Assume that different shapes indicate alleles of different genes and that the same shape but different shade indicates alleles of the same gene A list of terms that may be useful. NOTE: you needn’t limit your use of jargon to this list as I may have inadvertently omitted a useful term. suppression variable expressivity recessive lethal monogenic multifactorial polygenic genetic background stochastic effects incomplete penetrance polymorphic sex-limited/sex-influenced pleiotropic genetic heterogeneity (heterogeneous trait) probabilistic propensity complementation epistasis modifier haploinsufficient Shaded circles = Affected (Addictive personality) Unshaded and double circles = Unaffected Section 3


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