1. Pedigrees & Human Diseases
Additional Topics in Genetics
Bio 391

2. PEDIGREES  another way to study inheritance

3. How to read a pedigree…
Carrier female
Carrier male

4. 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)

5. 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

6. 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??

7. 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

8. 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

9. In utero testing to determine if a child will have a disorder
Amniocentesis – sample of fluid surrounding fetus, contains some fetal cells
Fig a
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

10. Chorionic villus sampling (CVS)
Pieces of tissue (chorion connecting mother and fetus) are removed
Fig b
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

11. 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

12. 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