Title: 14.3-14.4 Notes Name: Sabrina Rodriguez Chapter Number: 14 Date: 11/16/20 Period: 3 AP Biology | Mrs. D. Escobar | 1
Concept 14.3: Inheritance patterns are often more complex than predicted by simple Mendelian genetics Page(s) Key Concepts/Terms Notes: Definitions, Illustrations, and Examples 280 Simple genetic basis --- -complete dominance incomplete dominance 281 - codominance -Each character is determined by one gene, for which there are only two alleles, one completely dominant and the other completely recessive. -In Mendel's classic pea crosses, the F1 offspring always looked like one of the two parental varieties because one allele in a pair showed complete dominance -the situation in which the phenotypes of the heterozygotes and dominant homozygote are indistinguishable. -neither allele is completely dominant, and the F1 hybrids have a phenotype between those of the parental varieties. -the situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele. - example of incomplete dominance- All the F1 hybrids have pink flowers. This third, intermediate phenotype results from flowers of the heterozygotes having less red pigment than the red homozygotes. P Generation Red White C"CW Ganetes F1 Generation Pink Gametes "C") Sperm F2 Generation Eggs Cick C"C" CTCW -in the variation, the two alleles affect the phenotypes in separate, distinguishable ways. -Interbreeding F1 hybrids produces F2 offspring with a phenotypic ratio of 1 red:2 pink: 1 white. -the segregation of the red flower and the white flower alleles in the gametes produced by the pink flowered plants confirms that the alleles for flower color are heritable factors that maintain the nit ian in antiman of hath Allalas And Ashilited in the
Key Concepts/ Terms Pages 282 283 j Dominant Dominant allele(roundtt Recessive allele(wrinkledtt Tay-Sachs disease -multiple alleles -dominant alleles can be rare fipolydactyly) -For example, the human MN blood group is determined by codominant alleles for two specific molecules located on the surface of red blood cells, the M and N molecules. -an allele is called dominant because it is seen in the phenotype, not because it somehow subdues a recessive allele. -When a dominant allele coexists with a recessive allele in a heterozygote, they do not actually interact at all. -To illustrate the relationship between dominance and phenotype, we can use one of the characters Mendel studied-round versus wrinkled pea seed shape. -A closer look at the relationship between dominance and phenotype reveals an intriguing fact: For any character, the observed dominant/recessive relationship of alleles depends on the level at which we examine phenotype. -an inherited disorder fia human genetic disease caused by a recessive allele for a dysfunctional enzyme, leading to accumulation of certain lipids in the brain. Seizures, blindness, and degeneration of motor and mental performance usually become manifest a few months after birth, followed by death within a few years. The brain cells of a child with Tay-Sachs disease cannot metabolize some lipids because of enzymatic activity. fi2 copies of the tay- sachs allele. -at the organismal level, the Tay-Sachs allele= recessive