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Transcript
Pedigrees & Human Diseases Additional Topics in Genetics Bio 391 PEDIGREES another way to study inheritance How to read a pedigree… Carrier female Carrier male • What do you think the F1 generation (line II) # 2 and #5 offspring represent? • Can you draw the Punnett Square for the Parent generation? (I) Pedigrees • Helpful because human breeding experiments are difficult • Show how traits are passed down through many generations • Based mostly on phenotypes; after the fact • Show the actual offspring – Punnett squares show the possible offspring • Really only works well for single traits – Not polygenic traits • Only works for inherited traits – Environmental factors play a large role in who we are Inheriting Diseases • Just like physical traits, some diseases can be inherited on our chromosomes. • And, just like physical traits, some are Xlinked, some are recessive, some are dominant or codominant. • Are you predisposed?? Human Genetic Disorders • When a genetic disorder is autosomal dominant, an individual with AA or Aa has the disorder. – Autosomal dominant disorders are rarely lethal – When a genetic disorder is autosomal recessive, only aa individuals have the disorder. – Recall carriers are usually healthy Prenatal Testing: • • • • Most children with recessive disorders are born to parents with a normal phenotype (carriers). A key to assessing risk –identify carrier status Recently developed tests for several disorders can distinguish between normal phenotypes in heterozygotes from homozygous dominants. The results allow individuals with a family history of a genetic disorder to make informed decisions about having children. However, issues of confidentiality, discrimination, and adequate information and counseling arise. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings In utero testing to determine if a child will have a disorder • Amniocentesis – sample of fluid surrounding fetus, contains some fetal cells – Fig. 14.17a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Chorionic villus sampling (CVS) – Pieces of tissue (chorion connecting mother and fetus) are removed Fig. 14.17b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Ethical Dilemma • You are an employer and have 2 equally qualified candidates for a job. According to human resources, one of the candidates will develop Huntington disease and will likely be unable to work for longer than 10 years. What do you do? • GINA – Genetic Information Nondiscrimination Act of 2008 Genetic Disorders Gaucher disease Duschene Muscular Dystrophy Marfan syndrome Color blindness Hurler syndrome Hemophilia Lesch-Nyhan disease SCIDS Progeria Achondroplasia Edwards Syndrome Bloom’s syndrome Prader-Willi Syndrome Wilson’s disease Fragile X syndrome Tay-Sachs Albinism Cystic Fibrosis Sickle cell anemia PKU Lou Gehrig’s disease Cri du Chat syndrome Huntington Disease Turner’s syndrome Klinefelter syndrome Down syndrome Fanconi anemia