Lecture8DownSyndrome

21 one trisomic for chr 21 b 3 zygotes with normal

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21, one trisomic for Chr. 21 B. 3 zygotes with normal karyotype, one trisomic for Chr. 21 C. 2 zygotes trisomic for Chr. 21, two monosomic for Chr. 21 D. All 4 normal, because only non-disjunction in meiosis II can result in trisomy
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Brain regions affected in DS Hippocampus (long- term memory and spatial navigation center) Cerebellum (coordination, attention, language) Prefrontal cortex (decision making, social behavior, goal- orientation). Degeneration of basal forebrain
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Molecular basis of DS 1. Down Syndrome is caused by an extra copy of the long arm of human chromosome Human chromosome 21 (HSA21q) 2. ~ 50% increase in the expression of some of these genes presumably causes DS. 3. HSA21q contains over 500 genes. What is known about these genes? Which of them contribute to which aspects of DS? 4. Two approaches: A. Study DS patients with Chromosome 21 translocations of different lengths B. Mouse models
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Robertsonian translocations occur between acrocentric chromosomes 13, 14, 15, 21 and 22 http://www.nature.com/scitable/content/robertsonian-translocation-21763
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Robertsonian translocation in DS
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Korbel et al., (2009) The genetic architecture of Down syndrome phenotypes revealed by high-resolution analysis of human segmental trisomies. PNAS 106 (29), 12031–12036 Analyzed 30 DS patients with Robertsonian translocations Determined which genes were triplicated in each patient Correlated with the phenotype of each patient Tested the hypothesis: is there a particular region of chromosome 21 that is associated with specific phenotypes of DS (such as DSCR – Down Syndrome Critical Region)?
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IQ in segmental trisomy 21. VerLcal black bars at the right indicate the regions of segmental trisomy in individuals with IQs indicated above (thicker bars indicate regions of 4 copies). DS paLents Korbel et al. (2009) Fig. 3E
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IQ in segmental trisomy 21. DS paLents Korbel et al. (2009) Fig. 3E Do the data support the hypothesis that Down Syndrome Critical Region 1 is a major contributor to mental retardation in DS? A. Yes B. No DSCR1
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Down Syndrome – Alzheimer ` s connection -Deposition of amyloid beta A β observed starting in young age in the brain - Alzheimer ` s – like plaques and tangles observed by the age of 30 yrs - Alzheimer ` s - like dementia develops in 75% of Down syndrome individuals over 60 yrs of age - The gene for the amyloid beta precursor protein (APP) is located on chromosome 21 -Korbel et el. confirmed association between an extra copy of APP gene and Alzheimer ` s disease, but not mental retardation
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21 one trisomic for Chr 21 B 3 zygotes with normal...

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