Finals LEC Genetics

• Mutation


  A heritable change in the base sequence of DNA
• It is estimated that, on average, there is one copying error for every 1010 bases
• Mutations can occur


  1. During replication

  2. During transcription in protein synthesis (a non heritable error)
• Codons for Valine


  • CAT
  • CAC
  • CAG
  • CAA
• If the original codon is CAT

  It may be transcribed into mRNA as GUC which codes for Valine
• Other errors in replication may lead to a change in protein structure and be very harmful
• Mutagen


  A chemical that causes a base change in DNA
• Nucleotide excision repair (NER)


  • Can prevent mutations by cutting out damaged areas and resynthesizing them
  • Not all mutations are harmful, certain ones may be beneficial because they enhance the survival rate of the species
• Recombinant DNA


  DNA from 2 sources that have been combined into one molecule
• Plasmid


  A small, circular, double-stranded DNA molecule of bacterial origin
• Restriction endonucleases


  A class of enzymes that cleave DNA at specific locations
• One restriction endonuclease may be specific for cleavage of the bond between A-G in the sequence -CTTAAAG-
• Cloning DNA


  The cloning of human DNA fragments with a viral vector
• Fields of Genetics


  • Classical Genetics – Mendelian Genetics
  • Molecular Genetics – DNA, RNA, Gene Expression and Regulation
  • Cytogenetics – Chromosomes, Chromosomal Aberrations, Patterns of Inheritance
  • Human Genetics – Heredity & Variations in Human, Human Genetic Disorders, Epigenetics
  • Medical Genetics – Cancer Genetics, Pharmacogenetics, Genetics in Clinical Settings
  • Population Genetics – H-W Equilibrium, Genetic Differences Within and Between Pop'n
• Epigenetics


  Any gene-regulating activity that doesn't involve changes to the DNA code. The gene expression changes but the genes themselves don't. Epigenetics adds an additional level of complexity to the genetic code. Can persist through one or more generations. The science that studies heritable changes of DNA not involving changes in DNA sequence that regulate gene expression.
• Epigenetics


  • Involves chromatin remodeling, DNA methylation, histone modification, microRNA expression
  • Includes twin studies (Concordant & Discordant), X-chromosome inactivation, environment & lifestyle
• Epigenetics is the addition or deletion of a CH3 group to a DNA base, turning the gene on or off, or to packaging of the chromatin structure by silencing or opening regions of the genome by winding or unwinding the DNA around histones
• Epigenetic changes are more common than mutations that change the actual structure of the DNA
• DNA Methylation


  An epigenetic mechanism that occurs by the addition of a methyl (CH3) group to DNA, thereby often modifying the function of the genes and affecting gene expression
• The most widely characterized DNA methylation process is the covalent addition of the methyl group at the 5-carbon of the cytosine ring resulting in 5-methylcytosine (5-mC), also informally known as the "fifth base" of DNA
• Methyl groups are added to DNA by enzymes called DNA methyltransferases (DNMTs) assisted by S-adenosylmethionine, an intermediate of methionine
• Errors in the epigenetic process, such as modifying the wrong gene or failing to add a compound to a gene, can lead to abnormal gene activity or inactivity, and cause genetic disorders
• Genomic Imprinting


  A reversible form of gene inactivation and is not considered a mutation. The ability of a gene to be expressed depends upon the sex of the parent who passed on the gene.
• Genomic imprinting affects gene expression by chemically modifying DNA and/or altering the chromatin structure. Often, genomic imprinting results in a gene being expressed only in the chromosome inherited from one or the other parent.
• Epigenetic changes caused by exposures to environmental factors can be transmitted down several generations
• Studies on effects of Dutch Hunger Winter


  • Increased risk of glucose intolerance, coronary heart disease, obesity, schizophrenia, breast cancer, and drug addiction in individuals conceived during the famine
• Audrey Hepburn suffered from jaundice, anemia, respiratory problems and chronic blood disorders due to food deprivation during the Dutch Hunger Winter, which may have led to her slim figure and health problems later in life
• Diseases caused by epigenetic aberrations may be treatable and preventable through preventative health care, diet, exercise, and stress management
• Epigenetics provides strange patterns of inheritance such as genomic imprinting, the yellow/agouti Avy mouse, and the all-female tortoiseshell (Calico cats)
• Gene regulation


  The process of turning genes on and off in cells, most commonly occurring at the level of transcription
• Transcription factors bind to regulatory regions of a gene and increase or decrease the level of transcription
• Legislations/Laws addressing genetic issues in the Philippines


  • The Newborn Screening Act of 2004, Republic Act No. 9228
  • The Rare Disease Act of 2016, Republic Act 10747
  • Article 38 of the Family Code of the Philippines
• The reason for the prohibition on marriages between close blood relatives in the Family Code is that such marriages usually result in degenerate children with organic defects
• DNA has a greater impact on an individual's criminal tendencies

  Environment has a greater role in depressive disorder in men
• Twin study


  Helps geneticists understand the different traits that are affected more by nature (DNA) vs nurture (the home environment)
• Differences between identical twins raised in the same environment can be explained by epigenetics
• Epigenetic marks can be transmitted through generations
• GR Methylation


  DNA methylation predominantly takes place at discrete CpG sites in the genome regions where cytosine nucleoti
• If a mother smokes, the stressors that she encounters at home or at work


  Can be transmitted as chemical signals through her bloodstream to her developing fetus
• Epigenetic marks


  Marks that sit on the fetus' DNA and affect its long term health