Presentation on theme: "Chapter 11 Complex Inheritance and Human Heredity"— Presentation transcript:
1Chapter 11 Complex Inheritance and Human Heredity 11.1 Basic Patterns of Human Inheritance
2Recessive Genetic Disorders Mendel’s work went unnoticed by the scientific community for about 30 years then it was rediscovered in the early 1900s.At that time many scientists were interested in the cause of diseases and noticed that some diseases “ran in families”.Alkaptonuria was the first identified (recessive) genetic disorder. Alkaptonuria, from an enzyme deficiency, causes black acidic urine and later in life affects bones and joints.
3Recessive Genetic Disorders A recessive trait is expressed when the individual is homozygous recessive for the trait.Both parents would need to have at least one recessive allele.Usually the parents are heterozygous (carriers) for the disorder.
5Cystic FibrosisAffects the mucus-producing glands, digestive enzymes, and sweat glandsChloride ions are not absorbed into the cells of a person with cystic fibrosis but are excreted in the sweat.Without sufficient chloride ions in the cells, a thick mucus is secreted
10Tay-Sachs DiseaseCaused by the absence of the enzymes responsible for breaking down fatty acids called gangliosidesGangliosides accumulate in the brain, inflating brain nerve cells and causing mental deterioration.Death by age 2
11Dominant Genetic Disorders 99.9% of population is homozygous recessive for achondroplasia
12Huntington’s Disease Affects the nervous system Latent disorder affects age 30 to 50Gradual loss of brain function (“holes” in brain)Genetic test availableResult of allele mutation at tip of chromosome #4
13Achondroplasia Most common form of dwarfism 75% of individuals born to parents of average size, result of new mutationLethal spontaneous abortion in homozygous dominant genotype
15Pedigree Analysis Are females Are males Shaded in circles and squares are affected individualsRoman Numerals (I – IV) are generationsLines across represent matingLines down represent offspring
16Pedigree AnalysisCount the number of affected males and affected females. If most males and few or no females most likely sex linked trait.Look at the affected individuals. If every individual with the trait has a parent with the trait then this trait is dominant. If non-affected parents produce an offspring with the trait then it is recessive.Determine the phenotype and genotype of every individual
17Pedigree Analysis Affected males: 1 Affected females: 2 (not sex linked)No affected individual has parent with the trait, means recessiveAll affected individuals would be homozygous recessive, aaAll parents of affected individuals would be heterozygous, AaSiblings of affected individuals would be heterozygous (Aa) or homozygous dominant (AA)