NURS 501-Exam 2 all required to ace your tests

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What is Linkage • DNA variant is said to be linked to disease that means that the variant is very close to the disease gene on the same chromosome • A disease gene and the variant will be inhe... rited together instead of independently assorting Unlinked Genes • F=dominant normal allele • f = recessive CF allele • T=dominant tongue roller allele • t = recessive non-roller allele • FfTt X FfTt – 9/16=roller, no CF – 3/16=roller, has CF – 3/16=non-roller, no CF – 1/16=non-roller, has CF Example of Linked Genes • Ratio is significantly different • P= purple flower • p= red flower • L=long pollen • l= round pollen • PpLl X PpLl • 11/16=purple, long • 1/16= purple, round • 1/16= red, long • 3/16= red, round Genetic Mapping • Determining the linear order of genes/markers down a chromosome. • Amount of recombination = distance • The frequency of recombination (crossing over) helps us build maps Video: http://www.youtube.com/watch?v=op7Z1Px8oO4&feature=related Example p l P L PpLl X PpLl P L l L l p p P No Recombination Recombination Polymorphism Example • Autosomal Dominant – D= abnormal (PKD) – d= Normal • Alleles: 1,2,3,4 • In pedigree: Red=PKD Dad (PKD) Mom (normal) 1 D 2 d 3 d 4 d 3 d 1 D 1 D 4 d 2 D 3 d 2 d 4 d 1 D 3 d 1 D 2 d 3 d 4 d Recombinant More Recombination 1 D 2 d 3 d 4 d 1 D 1 D 2 d 2 d 2 D 3 d 3 d 4 d 4 d 4 d Doesn’t Fit Non Recombinant -Recombinants D=PKD allele d= normal allele Linkage • Distance between PKD gene and DNA variant: • #of recombinant offspring X 100 Total # of offspring Linkage Example • Family #1 0/5 • Family #2 1/7 • Family #3 1/8 • 0+1+1 X 100 = 2 X 100 = 10 cM 5+7+8 20 cM • cM= centimorgan – Unit of distance on a genetic map – 1 cM = approximately 1 million bases of DNA – Also represents 1% recombination frequency Back to linkage example • Add a 4th family → distance may change • Family #4 3/5 • 0+1+1+3 X 100 = 5 X 100 = 20 cM 5+7+8+5 25 Linkage Analysis • Linkage analysis is used when you want to narrow down the region or regions of the genome that house a gene for the condition you’re investigating Video: http://www.youtube.com/watch?v=b_Iypzk5vGc LOD Score • LOD (logarithm (base 10) of odds) • Measurement that tells you what the likelihood is that there’s linkage between your DNA variant and the disease gene [Show More]

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