1. Biology Chapter 11 Human Genetics

2. Human Genetic Disorders  Can be recessive disorders  In some cases, can be dominant disorders  We are going to look at some examples of some genetic disorders.  NO TEST this chapter. Your test instead will be:  Pick a genetic disorder to research  Complete one of the following:  3-5 page typed double-spaced paper on your research  Slide presentation with slide number between 18-23 slides  Work cited page (or slides) does not count toward total but is necessary to document your work.

3. Cystic Fibrosis  Most common inherited genetic disorder among white people. 1 in 20 carries the recessive allele.  1 in 2000 babies born with CF.  Symptoms:  Thick mucus builds up in lungs, can damage pancreas.  Movement of salts and water across cell membranes affected.  Medical advances have helped, but disorder is still fatal.

4. Huntington’s Disease  Caused be a dominant gene.  Why does this matter?  Estimated that 25000 Americans have the disorder.  Changes in coordination occur  Difficulty thinking through problems  Depressed irritable mood  Diminished speech and difficulty swallowing.  In late stages, individual is totally dependent on others.

5. Sickle-Cell Anemia  Found most often in blacks.  1 in 500 African-Americans has the disorder  Hemoglobin structure is changed.  Severe pain, fever, and weakness are symptoms of the blood cells becoming caught in capillaries.  Strokes that result in paralysis can result.

6. Analysis  Solving genetic problems is similar to putting together a puzzle.  Some are simple, if the mutant gene is singular.  Diabetes mellitus, heart disease, and some personality disorders are the result of multiple mutant genes.  Estimated every person carries 5 to 8 harmful genes.  Most of the harmful alleles are recessive.  Also thought that most zygotes carrying harmful alleles never complete development.  3/5 of all pregnancies in humans are aborted (most naturally)

7. Heterozygote Superiority  Sometimes, the heterozygous combination of alleles is an advantage: Sickle cell anemia  In Africa, as many as 40% carry the heterozygous form.  Although this makes hemoglobin function less efficient, for a simple reason, it also makes the individual resistant to malaria.  The parasite that causes malaria does not do well in sickle shaped cells.  Survival rate of heterozygotes is higher than those who don’t carry the gene for the disorder.

8. Chromosome Abnormalities  Nondisjunction – failure of paired chromosomes to separate during meiosis.  Down syndrome - #21 chromosomes fail to separate. Known as trisomy 21.  Varying degrees of mental retardation  Usually shorter than normal  Heart, intestinal, or visual problems  Susceptible to infection and increased risk of blood cancer (leukemia)  Most likely to occur to infants of mothers over 40.  Karyotyping can help in chromosome abnormality detection.

9. Sample Kayotype

10. 11.2 Prevention  Genetic counseling – giving parents information about chances of their children having a genetic disorder.  What would you do if there was an increased chance of a child with a genetic disorder?  Diagnosis in the uterus:  Amniocentesis – needle used to withdraw fluid from the fetus and karyotype is done. Can be done in 14 th week.  Chorionic villus biopsy – 9 th week, cells from chorion are withdrawn.  Ultrasounds and fetoscopy also offer chances for early detection.