HLTH 335 1st Edition Lecture 6Chapter 5: Heredity & CancerObjectives:-Describe DNA’s composition and its role in heredity-Describe general mechanisms of transmission of hereditary diseases and give examples-Explain genetic diseases based on abnormal chromosome construction-Discuss screening techniques and the concept of gene therapy-Distinguish between congenital and hereditary conditionsHeredity: The Basics-DNA = the blueprint for directing cell activities-Chromosomes = assembled strands of DNA within the nucleus-44 autosomes (22 pairs)-2 sex chromosomes: -Female: XX Male: XY-Karyotype = the complete chromosomal composition-Chromosomes can be extracted from the nucleus & photographed under a microscope in order to detect abnormalities.Genetic Inheritance:-Genes for a particular trait (e.g., hair color) occupy a particular site on a chromosome.-Each person has 2 copies of each gene; 1 from each parent.-Alleles = alternate forms of a gene. -Homozygous – the same (e.g., BB or bb)-Heterozygous – different (e.g., Bb)-Dominant – when only one allele is need to express a trait (e.g., Bb results in brown hair)-Recessive – when two are needed to express a trait (e.g., the red hair allele is recessive)Autosomal Dominant Diseases:-Occur through transmission of a dominant allele.-Offspring have 50% chance of being affected, if one parent has normal karyotype.-Males and females have equal chance of being affected.Examples of Autosomal Dominant Diseases:-Polydactyly (having extra fingers or toes)-Achondroplasia (autosomal dominant)-Abnormal cartilage formation-Marfan syndrome (autosomal dominant)-The connective tissue protein -“fibrillin” is missingThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-(people are tall and thin, believe Lincoln had it)-Familial hypercholesterolemiaAutosomal Recessive Diseases:-Disease manifests when individual is homozygous for the defective allele.-Heterozygous parents are carriers; they do not have the disease.-Child has a 25% chance of being affected.-Recessive allele appears more frequently in close intermarriages.Examples of Autosomal Recessive Diseases:-Sickle cell anemia-The black population most at risk-1 in 12 are carriers-Hemoglobin is abnormal, results in deformed red blood cells-Deformed cells lodge and block circulation-SUPER INTERESTING FACT: (!)-Heterozygous individual does not have the disease, but will experience mild anemia, BUT…-The defective allele confers increased resistance to malaria, which kills 2 million people a year!Watch this: http://www.youtube.com/watch?v=2CsgXHdWqVsMore Examples:-Galactosemia-Tay-Sachs disease-Albinism(Be able to tell everything you know about one of these. Ex: incidence rate, who is most affected, etc)Sex-Linked Inheritance:-Defective gene on X chromosome.-Y chromosome is small and carries few genes.-Defective X on male is unmasked, so the trait is expressed. (less common for women to develop X related diseases).-Far less common for females to inherit x-linked diseases.-Heterozygous female is carrier for the disease.-Male transmits the defective allele to his daughters.Examples of Sex-Linked Diseases:-Color blindness: inability to distinguish colors, specifically between red and green.-Rare in women-Occurs in 1 out of 10 men-Hemophilia-Inactivation of an intrinsic clotting factor causes bleeding for longer period of time than normal. -NOT “faster” or “more profuse” bleeding (just bleeding for longer periods of time)Abnormal Chromosome Diseases:-… as opposed to diseases caused by defective genes, like we’ve discussed so far.Potential problems:-Altered number or structure of chromosomes-Failure of chromosome to separate during cell division-Complete loss of autosome (usually incompatible with life; leads to spontaneous abortion).Down Syndrome:-Trisomy of small chromosome 21 (have 3 rather than 2).-Many fetuses are aborted early in pregnancy (70-75%) (spontaneously: miscarriages) -Incidence: 1 out of 800-Higher with advancing maternal age: 1 in 50 if mother is > 40 years old-Characteristic appearance; mild to moderate mental retardation.Down Syndrome: Common Complications:-Heart defects (~ half of all with DS)-Leukemia (more likely to develop in young children with DS)-Infectious Diseases (more susceptible due to abnormalities in immune system)-Dementia (often begins before age 40)-Sleep Apnea (soft tissue/skeletal abnormalities lead to obstruction of airways)-Obesity-Other: gastrointestinal blockage, thyroid problems, early menopause, seizures, hearing loss, premature aging, skeletal problems, poor vision.Down Syndrome: Life Expectancy- 70-75 % of DS babies will die in uteroOf live births:-15% die before one year of age-35% die before 50 years of age-50% live beyond 50 years of ageFACT: In 1929, > 50 % only lived to age 10.More Examples of Abnormal Chromosome Diseases:-Cri Du Chat Syndrome-Turner Syndrome-Klinefelter Syndrome-Hermaphrodites(Pick one of these or one out of the previous 3 to know about for the test)Genetic Counseling:-A genetic counselor usually begins with a complete family history of both prospective parents.-A complete, detailed family history is called a pedigree.-Pedigrees demonstrate the pattern of inheritance of a genetic disease within a family.-When the pedigree is complete, the genetic counselor can inform prospective parents of the possibility of having genetically abnormal offspring, and they can make an informed decision.Diagnosis of Genetic Diseases:-Early diagnosis is critical to prevention and treatment of genetic diseases.-During amniocentesis, a small amount of amniotic fluid is withdrawn after the 14th week of pregnancy. -Amniocentesis can detect approximately 200 genetic diseases.Gene Therapy:-A procedure that involves identification, manipulation, and transference of genetic segments into a hostto replace defective genes and to perform desired genetic activities.-The genetic material used is compatible with human DNA that may be cultured in a microbe and delivered in a viral package or by injection.-Also referred to as genetic engineering.Congenital Diseases:-Appear at birth or shortly after, but they are not caused by genetic or chromosomal abnormalities.-Congenital defects usually result from some failure in development during the embryonic stage, or in the first 2 months of pregnancy. Therefore, congenital diseases cannot be transmitted