Exam 3 Biology

• Mendel's Law of Segregation I


  Alleles of one gene segregate in meiosis (passed to offspring)
• Mendel's Law of Segregation II

  Individuals possess 2 alleles, parent passes only 1 to offspring
• Law of Independent Assortment


  Each pair of alleles on different chromosomes (unlinked) segregate independently from each other during meiosis
• Women have XX sex chromosomes, men have XY sex chromosomes
• Humans have 23 pairs of homologous chromosomes, 22 pairs autosomal and 1 pair sex chromosomes
• Extensions of Mendel's Laws


  • Incomplete dominance
  • Multiple alleles
  • Codominance
  • Pleiotropy
  • Polygenic inheritance
  • Environmental effects
• Gene linkage


  Alleles on the same chromosome are linked and do not segregate independently
• There are 4 blood types: A, B, AB, O
• Sickle cell anemia, skin and eye color are examples of pleiotropic effects
• Environment can affect phenotype, e.g. skin color with sun exposure
• Genotype


  Complete set of genes
• Phenotype


  Observed physical and functional traits
• Allele


  Alternative form of a gene, arising by mutation
• Homozygous


  Organism has identical alleles for a gene
• Heterozygous


  Organism has different alleles for a gene
• Hybrid


  Offspring of two different varieties
• Dominant allele


  Gene always expressed, even if heterozygous
• Recessive allele


  Two copies of the gene needed to be expressed, must be homozygous
• Punnett square


  Used to predict patterns of inheritance
• Aneuploidy


  Abnormal chromosome number
• Euploidy


  Normal chromosome number (46 in humans)
• Down syndrome is caused by trisomy 21 (extra chromosome 21)
• Chromosome abnormalities


  • Deletion
  • Duplication
  • Inversion
  • Translocation
• Apoptosis is programmed cell death
• Central Dogma of Gene Expression


  1. DNA transcription to RNA

  2. RNA translation to protein
• Transcription


  Produces generic messages in the form of RNA
• mRNA


  Messenger RNA, takes information from nucleus to cytoplasm
• tRNA


  Transfer RNA, takes information from mRNA and translation into sequence of amino acids (protein)
• rRNA


  Ribosomal RNA, assembles ribosomes
• Autosomal recessive disorders


  • Albinism
  • Cystic fibrosis
  • Galactosemia
  • Phenylketonuria
  • Sickle cell disease
  • Tay-Sachs disease
• Autosomal dominant disorders


  • Achondroplasia
  • Alzheimer's disease
  • Huntington's disease
  • Hypercholesterolemia
• 1. linked disorders/traits


  • Red-green color blindness
  • Hemophilia
  • Duchenne muscular dystrophy
• Sex chromosome abnormalities


  • Klinefelter syndrome (XXY)
  • Turner syndrome (XO)
• Recombinant DNA


  DNA created by combining fragments from different species
• Steps in cloning a gene

  1. Isolate plasmid DNA

  2. Isolate DNA with target gene

  3. Cut plasmid with restriction enzyme

  4. Insert target DNA into plasmid

  5. Insert plasmid into bacteria
• Vector


  DNA molecule that carries foreign DNA into host cell
• CRISPR


  Gene editing tool that allows altering an organism's genome
• The Human Genome Project identified 3.2 billion base pairs and 24,000 genes
• Epigenetics


  Molecular mechanisms that regulate gene expression without changing DNA sequence, influenced by factors like diet, exercise, stress, etc.