Non-mendelian inheritance

• Sex-linked traits refer to traits determined by a gene on a sex chromosome, usually X.
• For mammals, sex is an inherited phenotypic trait.
• Sex chromosomes separate in meiosis just like every other homologous pair.
• Sex-linked recessive traits are those where a male exhibits the trait if he has a recessive X, while a female only exhibits the trait if she is homozygous recessive.
• Sex-linked recessive mutations can be detected using pedigrees.
• Female mammals have one X chromosome in each cell, which is randomly inactivated.
• Most traits are quantitative, meaning the phenotype is continuous and influenced by multiple genes and the environment.
• Polygenic inheritance is when multiple genes affect a single trait.
• Global skin color is also polygenic, with two types of melanin: Eumelanin (black and brown pigments) and Pheomelanin (yellow to pinkish-red pigments).
• Human hair color is also polygenic, with brown pigment formed by additive effects of two dominant alleles, lightest pigment formed by 3 recessive copies, and only pheomelanin produced.
• The environment also influences an organism’s phenotype for most traits.
• Hydrangea color depends on soil pH, Siamese cat coat color is due to a temperature-sensitive enzyme, and human diseases can be affected by genes with different effects in different environments. These are examples of what?


  Environmental influences
• When reaction norm lines are not parallel, the environment interacts with the genotype.
• Is this a genotype x environmental interaction?

  
• Does this have a genotype x environmental interaction?

  
• Who is Thomas Hunt Morgan?

  Thomas Hunt Morgan studied fruit fly genetics. His experiment had red female x white male and crossed their kids and their kids.
• The F1 generation of Morgan's experiment had all offspring with red eyes
• Autosomes are non-sex chromosomes and have 22 pairs.
• Pleiotropy occurs when one gene influences two or more seemingly unrelated phenotypic traits.