Name:____________________________________________ Date:____________________ Genetics Notes: Patterns of Inheritance & Pedigrees I. Other Patterns of Inheritance: **Not all traits are completely dominant** A. Incomplete Dominance 1. Pattern of inheritance in which heterozygous offspring show a phenotype between the phenotypes of the parents (in the middle) 2. NEITHER allele is expressed fully 3. Examples: a. Snapdragon flowers: i. Red flower + white flower = PINK flower b. Cow color: i. Red (brown) bull + white cow = Roan (Pink) cow 4. Punnett Square Example: a. Knowing that a certain flower shows a pattern of incomplete dominance, create a Punnett Square showing a cross of TWO PINK flowers. b. r = red; w = white B. Codominance 1. Pattern of inheritance where both alleles in the heterozygous offspring are FULLY expressed 2. Example: Human Blood Type a. Genotype = Letters; Phenotype = Blood Type b. Type A: AA, AO (homozygous & heterozygous) c. Type B: BB, BO (homozygous & heterozygous) d. Type AB: AB (ONLY heterozygous) e. Type O: OO (ONLY homozygous) 3. Punnett Square Example: a. Knowing that blood type shows a pattern of codominance, cross a person with TYPE O blood and one with TYPE AB blood. Name:____________________________________________ Date:____________________ C. Sex-linked 1. Phenotypic expression of an allele that is dependent on the gender of the individual 2. Carried on either sex chromosome (X or Y) a. Remember: Female = XX; Male = XY b. Many more genes carried on the X chromosome, so many more X-linked traits than Y-linked traits i. Examples: Hemophilia, Color-blindness ii. FEMALES: If have only healthy X, it dominates over the infected X. iii. MALES: If have only one infected X, Y can’t dominate over it. 3. Punnett Square Example a. Knowing that COLOR BLINDNESS is a sex-linked trait, cross a CARRIER FEMALE with a NON-INFECTED MALE. b. Determine the probability of this couple having a color- blind child. D. Polygenic Traits 1. One trait is controlled by TWO or MORE genes 2. Example: a. Human skin color E. Multiple Alleles 1. More than two alleles for the same gene Name:____________________________________________ Date:____________________ 2. Example: a. Human blood type (phenotypes produced by 3 different alleles) F. Pleiotropy 1. Single gene affects MORE than one trait 2. Examples: a. Sickle cell disease b. Marfan’s syndrome II. Pedigree A. Chart that shows how a trait and the genes that control it are passed through a family 1. Most knowledge of human genetics comes from studying patterns of heredity in populations and families 2. Best way to trace these patterns is by creating a pedigree B. Symbols: Symbol Description Unaffected male Unaffected female Affected male Affected female Deceased (dead) male Name:____________________________________________ Date:____________________ Deceased (dead) female Possibly affected male or unknown Possibly affected female or unknown Carrier male of autosomal recessive disorder Carrier female of autosomal recessive disorder Connected Symbols: Twins Married couple Divorced Couple Siblings Pedigree Example: I II III I Although Jane and Joe Smith have dimples, daughter, Clarisse does not. Joe’s dad has dimples, but his mother and his sister, Grace, do not. Jane’s dad, Mr. Renaldo, her brother, George, and her sister, Emily, do not have dimples but her mother does. .