unit 5

• Living things are currently classified into one of three domains of life: Archaea, Bacteria, and Eukarya
• The secret code of life has to be stored in DNA and RNA and passed on from one generation to the next
• All organisms are linked through shared common ancestry
• Homologous chromosomes


  Similar size and carry similar but not identical information
• Meiosis


  1. Prophase 1

  2. Metaphase 1

  3. Anaphase 1

  4. Telophase 1

  5. Prophase 2

  6. Metaphase 2

  7. Anaphase 2

  8. Telophase 2

  9. Cytokinesis
• Meiosis


  • Reduces chromosome number
  • Occurs in sex organs
  • Includes crossing over
• Meiosis vs Mitosis


  • Purpose: Meiosis forms gametes, Mitosis grows/repairs/reproduces asexually
  • Meiosis creates 4 genetically unique haploid cells, Mitosis creates 2 identical diploid cells
  • Meiosis involves crossing over and independent assortment, Mitosis does not
  • Meiosis separates homologous pairs then sister chromatids, Mitosis separates sister chromatids only
• Gregor Mendel


  Austrian monk and farmer, father of heredity
• Mendel's Laws


  • Law of Independent Assortment: Alleles on different chromosomes separate independently
  • Law of Segregation: Alleles separate during meiosis
• Alleles


  Alternate forms of a gene
• Genotype


  Genetic makeup of an organism
• Phenotype


  Physical expression of a trait
• Solving genetic problems


  1. Identify patterns

  2. Use a reference key

  3. Reread the question
• Punnett squares and pedigrees are used to solve genetic problems
• Chi-square will be used to solve genetic problems
• Monohybrid cross


  • Purple flower (dominant) x White flower (recessive)
  • Genotypic ratio: 1 PP, 2 Pp, 1 pp
  • Phenotypic ratio: 3 purple, 1 white
• Distributive property


  In math it doesn't matter if Mom's sales are written across the top of the punnett square or down the side, you'll get the same answer
• Punnett square


  Each box within the punnett square has a restored diploid number representing a potential offspring when a gamete from each parent rejoins as homologous chromosomes during fertilization
• Interpreting the results of a cross, we have a 1:2:1 genotypic ratio with one homozygous dominant, two heterozygous, and one homozygous recessive</b>
• Phenotypically, there is a 3:1 ratio of purple to white, since purple is dominant</b>
• The white phenotype reappears in the F1 generation since both parents were carriers of the recessive allele</b>
• Completing genetic problems that follow two traits and a dihybrid cross

  1. Foil the parent genotypes to get each of their gametes, then distribute them into the offspring boxes

  2. A heterozygous cross needs a 16 box square and will produce a phenotypic ratio of 9:3:3:1
• Incomplete dominance


  Neither trait is fully dominant over the other, so both are partially expressed when present
• Incomplete dominance


  • Snapdragon flower with alleles for red and white, resulting in pink
  • Sickle cell trait, where a heterozygous individual has some normally shaped cells and some sickle shaped cells
• Multiple alleles and codominance

  Shown with blood typing, where there are three alleles (A, B, O) that can produce four primary phenotypes (A, B, AB, O)
• Punnett square for blood typing

  Produces all four blood types from a single cross
• Sex chromosomes


  • Females are genetically XX, males are genetically XY
  • The Y chromosome contains the SRY gene, leading to male characteristics
• Sex-linked traits


  Overwhelmingly located on the X chromosome and are recessive, so males express the trait if inherited
• Mendel's patterns were true for genes located on different chromosomes or far apart on the same chromosome, but genes located close together are often inherited together (linked)</b>
• Recombination frequency


  The number of offspring that show a recombination of traits not seen in the parental generation, used to calculate relative distance between genes on a chromosome
• Polygenic traits


  Traits that are the product of multiple genes, resulting in a phenotypic range within a population
• Epistasis


  When the phenotypic expression of one gene affects the expression of another gene, either depending on the other gene for expression or even masking or covering it up
• Non-nuclear inheritance


  Traits inherited from organelles like chloroplasts and mitochondria, which are only maternally inherited
• Phenotypic plasticity


  The ability of an organism to exhibit different phenotypes in changing environmental conditions, without a change in genotype
• Certain human genetic disorders can be attributed to the inheritance of a single changed allele or chromosomal error, like non-disjunction during meiosis</b>
• Pedigrees


  A tool used to analyze the patterns of inheritance of genes from parent to offspring, using squares for males and circles for females
• Analyzing pedigrees


  Look for patterns to determine if the trait is autosomal or sex-linked, dominant or recessive
• Homologous chromosomes and their alleles segregate during meiosis to form haploid gametes, unless a mutation or non-disjunction has occurred</b>
• Genetic variation is increased with crossing over, independent assortment, and random fertilization</b>
• Approaching genetic problems


  Read the prompt, identify the parental genotypes, complete a punnett square, and calculate the phenotypic and genotypic ratios