Chapter 11 Complex Inheritance and Human Heredity

Transcription

1 Chapter 11 Complex Inheritance and Human Heredity 11.1 Basic Patterns of Human Inheritance o The inheritance of a trait over can be shown in a o Pedigrees can help us to track and understand Genetic Disorders Review: = homozygous dominant = heterozygous = homozygous recessive o A recessive trait is only expressed if it is o If an individual is heterozygous for a recessive disorder, they are called a Types of Recessive Genetic Disorders: 1. Cystic Fibrosis o Affects the mucus producing glands, digestive and sweat glands. o are not absorbed into the cells of a person with cyctic fibrosis but are excreted in sweat o Without sufficient chloride ions in the cells, a 2. Albinism o Caused by, resulting in the absence of pigment in the skin and eyes o o o

2 3. Tay-Sachs Disease o Caused by the absence of the enzyme responsible for called gangliosides o Gangliosides accumulate in the, inflating brain nerve cells and causing. Types of Dominant Genetic Disorders You can be either or to inherit a dominant genetic disorder. 1. Huntington s disease o Affects the 2. Achondroplasia o Genetic condition that causes and limbs that are comparatively short Pedigrees o A diagram that traces the of a particular trait through several generations Pedigree Symbols o Normal Female o Female that expresses the trait o Female carrier (half shaded) o Normal male o Male that expresses the trait o Male who is a carrier for the trait o Pedigree Symbols o Roman Numerals (I, II, III, etc.) = number o Arabic numbers (1,2,3, etc) = in a particular generation

3 11.2 Complex Inheritance A. Incomplete Dominance o Heterozygous phenotype is an phenotype between the two phenotypes. o EX. Red x white = B. Codominance alleles are in the heterozygous condition. Example: Sickle-Cell Anemia o People who are have abnormal red blood cells that are shaped like a o Hemoglobin differs by. o Results in and blocked vessels o Those heterozygous for this trait produce of blood cells (normal and sickle) o Sickle cell anemia is most common in black whose families originated in and white Americans whose families originated in countries surrounding the. o 1 in 12 African Americans is for this trait.

4 C. Multiple Alleles Example1: Blood Type o The gene I has three alleles:,, o These alleles determine your blood type: and Importance of Blood Typing o Your immune system the red blood cells that you have. o If cells with a different protein enter your body, your will attack them! Genotype Surface Protein Phenotypes Example 2: Coat Color of Rabbits o Multiple alleles can demonstrate a hierarchy of dominance o In rabbits, four alleles code for coat color: and. D. Epistasis o Variety is the result of one allele the effect of another allele. o Example: Coat color in Labrador retrievers can vary from to.

5 E. Sex Determination o Sex chromosomes determine an individual s o Sex Linked Traits o Examples: 1. Color Blindness Carried on 2. Hemophilia Inability of blood to Carried on F. Polygenic Inheritance 1. Example: 2. Variation in skin color indicates that between and genes are involved 11.3 Chromosomes and Human Heredity A. Changes in Chromosome Number What would happen if an entire chromosome was missing or if you had an extra chromosome? o These mistakes often happen during. o Nondisjunction=chromosomes fail to properly during cell division 1. Unusual Numbers of Autosomes Most people have pairs of chromosomes autosome pairs & pair of sex chromosomes Some people have an extra chromosome (47 instead of ) Example: Down Syndrome o Caused by an extra Karyotypes are used to locate the extra chromosomes.

6 2. Unusual Number of Sex Chromosomes Many problems may exist: X missing =Turner s Syndrome, =death Extra X: =nearly normal female, =Male with Klinefelter s Syndrome Extra Y: =normal or nearly normal male Any individual with at least one Y is, and any individual without a Y is a.