1. Chapter 15: Human Genetics
Karyotypes, Down Syndrome, sex chromosomes, abnormalities, autosomal genes, sex-linked genes, and polygenic inheritance are covered in this Chapter.

2. Inheritance 0f Chromosomes
Somatic cells - 22 pairs of autosomes, 1 pair sex chromo
Karyotype - shows chromo’s paired by size, shape, & appearance in metaphase
members in a pair have same banding patterns

3. Inheritance 0f Chromosomes
Nondisjunction - occurs during meiosis, causing abnormal chromo #
Nondisjunction is the failure of one or more chromo’s to separate during MI or when daughter chromo’s fail to separate during MII.

4. Inheritance 0f Chromosomes
Down Syndrome - common autosomal trisomy
3 copies of chromo 21
23% cases sperm had extra chromo 21
chance of woman having down syndrome child increases w/ age.

5. Abnormal Sex Chromosomal Inheritance
Turner (XO) syndrome - females have only one X chromo
Females are short, broad chest, folds of skin on neck
Ovaries never functional, never undergo puberty

6. Abnormal Sex Chromosomal Inheritance
Klinefelter syndrome - males have one Y and 2 X chromos
individuals have large hands and feet and long arms and legs.

7. Abnnormal Sex Chromosomal Inheritance
Triplo-X females
Jacob syndrome (XYY)
Males w/Jacob’s syndrome are taller than average, have persistent acne, tend to have lower intelligence

8. Abnormal Sex Chromosomal Inheritance
Fragile X Syndrome - X chromo nearly broken, most often found in males
hyperactive or autistic children, delayed speech
Traced to excessive copies of CGG triplet

9. Autosomal Genetic Disorders
Males=squares, females=circles
Carrier- Has no apparent abnormality but can pass on allele for recessively inherited genetic disorder

10. Autosomal Dominant Disorders
Neurofibromatosis - have tan skin spots at birth that turn to benign tumors
1 in 3,000 people effected
Neurofibromas are lumps under the skin of nerves and other cells

11. Autosomal Dominant Disorders
Huntington Disease effects 1 in 20,000
leads to degeneration of brain cells
Death in years from onset
Gene for disease on chromo 4; contains repeats of CAG

12. Autosomal Recessive Disorders
Cystic Fibrosis - most common lethal genetic disease in Caucasions
1 in 20 is a carrier, 1 in 2,500 has disorder
Production of mucus in lungs and pancreas
Gene on Chromo 7

13. Autosomal Recessive Disorders
Tay-Sachs Disease - in Jewish people
Symptoms not apparent, child becomes blind & helpless, develops seizures.
Death by 3-y yrs.
Lack of enzyme hexosaminidase

14. Autosomal Recessive Disorders
Phenylketonuria(PKU)
1 in 5,000 births
Lack of enzyme needed to metabolize aa phenyalanine
Mutated gene on chromo 12
Child placed on low phenyalanine diet till age 7.

15. Beyond Simple Mendelian Inheritance
Polygenic Inheritance - 1 trait governed by 2 or more sets of alleles
Includes diabetes, schizophrenia, allergies, and cancers

16. Beyond Simple Mendelian Inheritance
Sickle-cell disease controlled by incomplete dominant alleles
Blood cells irregularly shaped (abnormal hemoglobin), clog vessels and break down
poor circulation, anemia, low resistnce to infection, jaundice...

17. Sex-linked Genetic Disorders
Traits controlled on sex chromo are sex-linked
Y-chromo smaller, most sex linked are on the X-chromo
Males get X-linked traits from mom
Daughter must have a carrier mom and an expressed dad.

18. Sex-linked Genetic Disorders
Color Blindness - recessive disorder involving mutations of genes coding for green or red sensitive cone cells
Cannot see red or green respectively

19. Sex-linked Genetic Disorders
Muscular Dystrophy - characterized by wasting away of muscles, eventually leading to death
1 in 3,600 births
fails to produce protein dystrophin
waddling gait, toe walking, frequent falls, difficulty rising.
Death by 20 yrs old

20. Sex-linked Genetic Disorders
Hemophilia - impaired ability to clot
1 in 10,000 males
Hemophiliacs bleed externally after an injury and also suffer internal bleeding around joints
Need blood transfusions or conc. of clotting protein