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

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

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.

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.

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

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.

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

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

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

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

Autosomal Dominant Disorders Huntington Disease effects 1 in 20,000 leads to degeneration of brain cells Death in 10-15 years from onset Gene for disease on chromo 4; contains repeats of CAG

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

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

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.

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

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...

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.

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

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

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