CHAPTER 11 Summary

• Genes, which code for proteins, are the units of inheritance, physically passed down from parents to offspring.
• An organism’s physical traits constitute its phenotype; its genes constitute its genotype. A person’s genotype can’t always be determined from his or her phenotype.
• Humans are diploid organisms, meaning they have two copies of each chromosome in their cells. Because chromosomes come in pairs, we have two copies of nearly every gene in our body cells. These copies can be the same or different from each other.
• Different versions of the same gene are called alleles. Alleles arise from mutations that change the nucleotide sequence of a gene.
• Alleles may be dominant or recessive. Dominant alleles can mask the effects of recessive alleles, which can be hidden.
• Many traits result from carrying two recessive alleles; others result from carrying one dominant allele.
• Meiosis is a type of cell division that produces genetically distinct sperm and egg.
• Homologous chromosomes recombine and assort independently during meiosis to generate genetically diverse sperm and eggs. No two sperm or egg cells produced by the same person will be exactly alike.
• Haploid gametes fuse randomly during fertilization, generating genetically unique diploid zygotes.
• A Punnett square can help predict a child’s genotype and phenotype when the pattern of inheritance, dominant or recessive, is known.
• Cystic fibrosis (CF) is a recessively inherited genetic disease. Alterations in the gene CFTR cause disease by interfering with ion and water balance in cells, especially in the lungs.

• MORE TO EXPLORE

  • Cystic Fibrosis Foundation www.cff.org/
  • Rock CF Foundation http://letsrockcf.blogspot.com/
  • FuCF (song) http://www.myspace.com/schallyeah
  • Pearson, H. (2009) Human genetics: One gene, twenty years. Nature 460:164–169. http://www.nature.com/news/2009/080709/full/460164a.html
  • Palca, J. (January 2, 2013) NPR: “Drug Fulfills Promise Of Research Into Cystic Fibrosis Gene” http://is.gd/wO3v2I
  • Ramsey, B. W., et al. (2011) A CFTR potentiator in patients with cystic fibrosis and the G551D mutation. New England Journal of Medicine 365:1663–1672.