Linkage and association mapping in genetic analysis

academics biology genetics
By Ryan R.

When geneticists want to see how closely related two genes are, they have two main ways of doing so: linkage analysis and association mapping. 

Linkage analyses use observation of phenotypes, or traits that can be observed, that are built into pedigrees, where the inheritance of specific traits are tracked in a family over time. Linkage refers to the fact that genetic markers or alleles of a gene that are close to each other on a chromosome generally segregate together. When alleles recombine (shuffle over) during meiosis, they are able to be inherited with a different chromosome, but this happens less often if the genes are closer to each other on the same chromosome. So, genetic markers (or alleles) that lie relatively far apart on a chromosome will undergo recombination more frequently than genetic markers that lie close to each other. These data are then made into genetic maps that correspond to the distance between different genes on a chromosome.  

Unlike linkage mapping, association mapping uses the newer technologies of DNA sequencing that allow scientists to identify many specific markers on a chromosome. Doing this over and over, and associating it with information from pedigrees, we can use our sequencing information to connect specific traits with a given sequence of DNA. Association mapping is generally carried out in the context of a whole genome, and this kind of study is called a Genome Wide Association Study (GWAS). Sequencing an entire genome is expensive, so instead, single nucleotide polymorphisms (SNPs) are used as molecular markers. SNPs are single sequence differences in DNA that are associated with a trait. For example, having an adenine at a given position in your DNA can be a SNP for having sickle cell anemia. Doing this thousands of times, with patients and controls, geneticists can identify individual or multiple genes responsible for traits, and start to find the locations of those genes on the chromosome. Unlike linkage analysis, which gives relative distances of genes, association mapping allows us to find the absolute position of genetic information.

Ryan graduated from Yale College with honors in Molecular, Cellular, and Developmental Biology, and completed the Multidisciplinary Academic Program in Global Health. He is currently a student at Harvard Medical School, and hopes to pursue a career in infectious diseases.

Comments

topicTopics
academics study skills MCAT medical school admissions SAT expository writing college admissions English MD/PhD admissions strategy writing LSAT GMAT GRE physics chemistry math biology graduate admissions academic advice ACT interview prep law school admissions test anxiety language learning premed MBA admissions career advice personal statements homework help AP exams creative writing MD study schedules test prep computer science Common Application summer activities history mathematics philosophy organic chemistry secondary applications economics supplements research 1L PSAT admissions coaching grammar law psychology statistics & probability legal studies ESL CARS SSAT covid-19 dental admissions logic games reading comprehension engineering USMLE calculus PhD admissions Spanish mentorship parents Latin biochemistry case coaching verbal reasoning DAT English literature STEM excel medical school political science skills AMCAS French Linguistics MBA coursework Tutoring Approaches academic integrity chinese letters of recommendation Anki DO Social Advocacy admissions advice algebra art history artificial intelligence astrophysics business cell biology classics diversity statement gap year genetics geometry kinematics linear algebra mechanical engineering mental health presentations quantitative reasoning study abroad technical interviews time management work and activities 2L DMD IB exams ISEE MD/PhD programs Sentence Correction adjusting to college algorithms amino acids analysis essay athletics business skills careers cold emails data science dental school finance first generation student functions graphing information sessions international students internships logic networking poetry resume revising science social sciences software engineering tech industry trigonometry writer's block 3L AAMC Academic Interest EMT FlexMed Fourier Series Greek Health Professional Shortage Area Italian Lagrange multipliers London MD vs PhD MMI Montessori National Health Service Corps Pythagorean Theorem Python Shakespeare Step 2 TMDSAS Taylor Series Truss Analysis Zoom acids and bases active learning architecture argumentative writing art art and design schools art portfolios bacteriology bibliographies biomedicine brain teaser campus visits cantonese capacitors capital markets central limit theorem centrifugal force chemical engineering chess chromatography class participation climate change clinical experience community service constitutional law consulting cover letters curriculum dementia demonstrated interest dimensional analysis distance learning econometrics electric engineering electricity and magnetism escape velocity evolution executive function freewriting genomics harmonics health policy history of medicine history of science hybrid vehicles hydrophobic effect ideal gas law immunology induction infinite institutional actions integrated reasoning intermolecular forces intern investing investment banking lab reports linear maps mandarin chinese matrices mba medical physics meiosis microeconomics mitosis mnemonics music music theory nervous system neurology neuroscience object-oriented programming office hours operating systems

Related Content