Chapter 1 - The Genetics Revolution

• If individuals with a certain gene variant contribute more offspring to the next generation than individuals who lack that variant, then the frequency of that variant will rise over time in the population.
• Mendel proposed that the factors that control traits act like particles rather than fluids and that these particles do not blend together but are passed intact from one generation to the next.
• Mendel’s particles are known as genes.
• Mendel proposed that each individual pea plant has two copies of the gene that controls flower color in each of the cells of the plant body ( somatic cells ).
• When the plant forms sex cells, or gametes (eggs and sperm), only one copy of the gene enters into these reproductive cells.
• Mendel’s two conclusions, (1) that genes behave like particles that do not blend together and (2) that one allele is dominant to the other, enabled him to explain the lack of blending in the first-generation hybrids and the re-appearance of white-flowered plants in the second-generation hybrids with a 3:1 ratio of purple- to white-flowered plants.
• Genetics involves the molecules involved in storage and expression of genetic information.
• The central dogma of molecular biology states that genes are made of DNA, which is transcribed to RNA molecules that serve as the template for protein synthesis.
• The central dogma of molecular biology states that the DNA helix undergoes transcription (RNA synthesis) to form mRNA.
• The central dogma of molecular biology states that the process of DNA replication enables each of the two daughter cells that result from cell division to have a complete copy of all the DNA in the parent cell.
• mRNA is the template for protein synthesis.
• In the central dogma of molecular biology, a codon is a set of three consecutive nucleotides in the mRNA that specifies an amino acid in a protein.
• Geneticists make special use of a small set of model organisms for genetic analysis.
• The opsin gene for blue light detection is on one of our non-sex chromosomes, or autosomes, for which both men and women have two copies—one copy from our mother and one copy from our father.
• Model organisms have features that make them well-suited for genetic studies, such as small size, small genome, large numbers of offspring, and short generation time.
• Geneticists working with the same model organism share stocks and information with one another.
• Red-green color blindness occurs in about 5 percent of people, mostly men, due to the green and red opsin genes being on the X chromosome.
• DNA polymerases can make a copy of a single DNA strand by synthesizing a matching strand with the complementary sequence of A’s, C’s, G’s, and T’s.
• Nucleases can cut DNA molecules in specific locations or degrade an entire DNA molecule into single nucleotides.
• Ligases can join two DNA molecules together end-to-end.
• DNA can also be “labeled” or “tagged” with a fluorescent dye or radioactive element so that the DNA can be detected using a fluorescence or radiation detector.
• Geneticists have developed methods to clone DNA molecules.
• The molecule is inserted into a host organism (often E. coli) where it is replicated many times by the host’s DNA polymerase.
• Having many copies of a gene is important for a vast array of experiments used to characterize and manipulate it.
• This process is called transformation, and it is possible, for instance, to transform genes from one species into the genome of another.
• The recipient species then becomes a genetically modified organism (GMO).
• Geneticists have developed an exciting new method called CRISPR/Cas9 that facilitates editing the genes of an organism and is expected to revolutionize not just laboratory genetics, but also medicine and agriculture.
• Like begets like is a principle observed throughout history, with children resembling their parents, the seed from a tree bearing flavorful fruit growing into a tree laden with flavorful fruit, and members of wolf packs showing familial resemblances.
• Adenine in one strand of DNA is always paired with thymine in the other by a double hydrogen bond, while guanine is always paired with cytosine by a triple hydrogen bond.
• The bonding specificity in DNA is based on the complementary shapes and charges of the bases.
• DNA is a double helix in which the nucleotide bases of one strand are paired with those of the other strand.
• Cells need mechanisms to turn genes on or off in specific cell and tissue types and at specific times during development.
• A protein-coding gene includes a regulatory DNA element (GGGCCC) to which a regulatory protein binds, the site where a group of proteins called the RNA polymerase complex binds to initiate transcription, and a protein-coding sequence.
• The regions of a protein-coding gene are arranged as follows: regulatory element followed by the site where the RNA polymerase complex binds, and the protein coding sequence.
• A regulatory protein binds with a regulatory DNA element which has a sequence “G G G C C C.” The RNA polymerase complex binds with the next site that follows.
• The direction of transcription is toward the right, from the left side of the protein coding sequence.
• The basic flowchart for information transmission in cells is known as the central dogma of molecular biology.
• Genes reside on chromosomes and are made of DNA.
• Genes encode proteins that conduct the basic enzymatic work within cells.
• The integration of classical genetics and genomic technologies allows the causes of inherited diseases to be readily identified and appropriate therapies applied.