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 X-linked, 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 Fragile X syndrome Tay-Sachs Albinism 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