Genetic Disorders inheritance patterns brief review - A Karyotype It’s a Boy!

Simple Heredity Simple Dominant Traits Cleft Chin Widow’s Peak Free-Hanging earlobes Almond-shaped eyes Hitch-hiker’s Thumb

Genetic Disorders caused by Recessive Alleles (4) 1. Cystic Fibrosis Recessive; defective membrane protein-chloride (protein) ion channels Mucus builds up in lungs, G I tract 2. Tay-Sach’s Disease * recessive *enzyme (protein) absent that breaks down a lipid stored in the CNS tissues * fatty acids accumulate in brain preventing nerve transmission. central nervous system; 3. Phenylketonuria Recessive Infants tested at birth Missing enzyme (protein) to metabolize phenylalanine ( amino acid). Excess phenylalanine builds up and is Toxic to the brain Control with diet WARNINGS ON NUTRASWEET ACTIVITY: Figure 12.3

4. Sickle Cell Disease Recessive: Hs = sickle cell allele ; H= normal allele Defective hemoglobin Sickle-shaped Red Blood Cells –Blocks blood flow, damages blood vessels, anemia ( Most common among African Americans and among others living in the tropics where malaria is prevalent. Homozygous= sickle Cell Disease (Hs Hs) –sickle=-shaped cells damage & block blood vessels; decreased life span; anemia, kidney and blood vessel damage. Heterozygous= sickle cell trait (H Hs) –Codominance make enough normal red blood cells, so healthy. –Heterozygotes--Advantage against Malaria causing parasite

Sometimes Dominant alleles are responsible for genetic disorders or abnormalities. Examples: 1. Huntington’s Disease (disease) –Onset between age 30 and 50 deterioration of nervous system Irreversible One in 10,000 in U.S. afflicted 2. Polydactyly (genetic abnormality) 6 fingers/hand DOMINANT

Any child born to a parent who has the allele for Huntington’s disease has a 50% chance of inheriting the disease and the disorder. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig

Changes in Chromosome Number Down Syndrome –Trisomy 21

Abnormal Numbers of Sex Chromosomes Male=has at least 1 Y chromosome Female= missing a Y chromosome XO, XXX, XXY, XYY Mostly sterile, some conditions result in mental retardation to some degree.

Sex-Linked Inheritance Traits controlled by genes located on sex chromosomes. Mostly the X – more genes than the Y –MORE MALES THAN FEMALES AFFECTED 1910 Thomas Hunt Morgan discovered genes linked to sex chromosomes—therefore –Eye color in fruit flies

Sex-linked genetic conditions/disorders Color-Blindness Hemophilia More common in _______________than _______________. Why? ( Do Problem-Solving Lab 12.3)

Sex-Linkage problems Which parent determines the sex of the offspring? What is the chance of having a boy? Girl? Suppose a man ( who has hemophilia) and a woman (is a carrier of hemophilia) have a girl. What is the likelihood of this girl having hemophilia?

p. 326 You cross 2 dark green ALF’s and produce 1 dark green, 2 light green and 1 white baby ALF’s. How would you explain this result? What is the probability that a couple will have a boy? A girl? P.326, P.S. Lab 12.3 What is the pattern of inheritance?