Bio

• Levels of genetic analysis

  • Classical Genetics
  • Molecular Genetics
  • Cytogenetics
  • Population Genetics

  
• Classical Genetics


  Describes the outcomes of Gregor Mendel's breeding experiments, also known as Mendelian Genetics
• Classical Genetics


  • Focuses on the physical observable (visible) results of breeding experiments, without analyzing the underlying molecules
  • Suggests that heredity is particulate and inheritance patterns can be explained through simple rules and ratios using Pedigrees and Punnett Squares

  
• Gene


  A hereditary factor that determines or influences a particular trait, comprised of a specific DNA sequence and located on a specific chromosome

  
• Allele


  A particular variant of a gene

  
• Genotype


  The particular collection of alleles found in an organism's DNA

  
• Homozygous


  An organism with two of the same alleles for a particular gene
• Heterozygous


  An organism with two different alleles for a particular gene
• Phenotype


  An organism's observable traits
• Dominant allele


  Produces its phenotype whether the organism is homozygous or heterozygous at that locus

  
• Recessive allele


  Produces its phenotype only when homozygous at the locus

  
• Carrier


  A person who is heterozygous for a recessive, disease-associated allele
• Principle of Segregation


  Each gamete carries only one allele for each gene because the two alleles separate during meiosis I
• Principle of Independent Assortment


  Alleles for different traits (genes) are segregated independently of each other because homologous chromosomes align randomly at the metaphase plate during meiosis I

  
• Mendel's laws


  Explained by the physical behavior of chromosomes during meiosis
• Monohybrid cross


  • Crossing pea plants with round vs wrinkly seeds
• Dihybrid cross


  • Crossing pea plants with round/wrinkly seeds and yellow/green seeds
• The number of possible gametes is 2^N, where N is the number of factors (genes)
• The size of the Punnett square needed is 2^N x 2^N, where N is the number of factors (genes)
• With n = 23 in human cells, there are over 8 million possible combinations of paternal and maternal genotypes in a potential offspring
• Determining possible offspring types and phenotypic ratios

  1. Use probability rules

  2. Faster and easier than using Punnett squares
• Number of possible gametes

  2^N, where N is the number of factors (genes)
• Size of Punnett square needed

  2^N x 2^N
• Punnett Square


  Chart that allows you to easily determine the expected ratios of possible genotypes in the offspring of two parents

  
• Mendel's law of segregation - the alleles in the gametes from each parent are written down the side and across the top of the Punnett square
• In a monohybrid cross, the probability of any single offspring showing the dominant trait is 3:1, or 75%

  
• Pedigree


  Chart that shows how a trait is passed from generation to generation within a family

  
• In an autosomal dominant trait, a child that has the trait will always have at least one parent with the trait
• In an autosomal recessive trait, two individuals without the trait can have a child with the trait
• DNA is the genetic material that encodes genetic information
• Watson-Crick model of DNA structure

  • Double helix
  • Base-pairing
  • Antiparallel orientation of strands
  • Types of bonds

  
• DNA replication


  1. Bidirectional from origin of replication

  2. Leading strand synthesized continuously

  3. Lagging strand synthesized in Okazaki fragments

  4. RNA primer required

  5. DNA polymerase adds nucleotides 5' to 3'

  
• Nucleic acid


  Linear polymer of nucleotides, each with a phosphate, sugar, and nitrogenous base

  
• Types of nucleic acids

  • DNA (deoxyribonucleic acid)
  • RNA (ribonucleic acid)

  
• DNA


  Double helix of complementary nucleotides, contains instructions for protein synthesis
• RNA


  Single-stranded, involved in protein synthesis (mRNA, tRNA, rRNA)
• Sexual reproduction


  A mode of reproduction involving a complex life cycle where the formation of new organisms occurs by the combination of genetic information from two different individuals of two different types (sexes)
• Process of sexual reproduction

  1. Formation of gametes with a haploid set of chromosomes

  2. Fertilization - two gametes combine to form a cell with a diploid set of chromosomes
• Sexual reproduction


  • Common in higher organisms like multicellular animals, some fungi, and plants
  • Absent in prokaryotes without nuclei but the process of bacterial conjugation, transformation, and transduction are similar
  • Characterized by the fertilization of a female gamete by a male gamete to form an offspring that is genetically different from both the parents
  • Bi-parental process requiring two different individuals of different sex
  • More complicated than asexual reproduction with specialized parts and cells involved
  • Formation of gametes with half the number of chromosomes is an important aspect
  • Reproductive cells undergo meiotic division to form haploid gametes
  • Requires two parental cells for the offspring to form
  • Slower process with less rapid production of offspring
  • Fertilization can be internal or external
  • Two types: allogamy (cross-fertilization) and autogamy (self-fertilization)
  • Further divided into syngamy (fusion of nuclei) and conjugation (fusion of hyphae or plasmids)
• Sexual reproduction is essential as it increases the genetic variation in the offspring