Spoken exam 2 material

• Fertilization in plants: pollen green adheres to the stigma, containing a generative and a tube cell. The pollen tube grows into the style while the generative cell travels to the ovule, forming two sperm. The pollen, then penetrates the ovule through the micropyle. one sperm fertilizes the egg, forming a zygote however, the other sperm will form an endosperm by fusing with two polar nuclei. The fertilized ovule forms the seed.
• Sexual reproduction in humans: mature human sperm, has only 23 chromosomes and mature human egg has only 23 chromosomes. During fertilization the chromosomes from the sperm and egg unite to give the fertilized egg a total of 46 chromosomes.
• another word for fertilized egg is zygote
• The particulate hypothesis: the idea that parents pass on discrete heritable units (genes).
• Mendel the father of genetics, was able to document a particulate mechanism through his experiment with garden peas
• Particulate unit factors:

  • Basic units of heredity
  • Passed unchanged from generation to generation
  • Determine various traits expressed by each individual plant
• Mendel’s postulates:

  • Unit factors exist in pairs. Genetic characters controlled by unit factors.
  • Dominance/recessiveness. In a pair of unit factors one unit unit is dominant and the other is going to be recessive.
  • Law of segregation. Paired unit factor segregate independently during gamete formation.
  • Law of independent assortment. genes independently during Gamete formation.
• (Mendels postulate)

  unit factors exist in pairs:

  • Different versions of genes account for variations in inherited characters
  • For example, the gene for flower color and P plants exist in two versions, one for purple flowers and the other for white flowers
  • Alternative versions of a gene are called alleles
• Regarding the purple or white flower, example the little for purple flowers only codes for the enzyme that helps synthesize purple pigment the white flowers do not have this enzyme
• (Mendel’s postulate)

  dominant/recessive:

  • For a pair of genes one gene is dominant the other is recessive.
  • If the two alleles are locus differ, the one determines the organisms appearance, and the other has no noticeable effect on appearance
  • Locus Refers to the place on a chromosome, where a gene is located
• dominant allele: determines the phenotype and is represented with a capital letter
• Recessive allele: has no effect on phenotype, but can still be past the next generation represented with a lowercase letter
• An organism inherit to alleles one from each parent, they can be either homozygous or heterozygous
• Homozygous: both alleles are the same
• Heterozygous: alleles are different when dominant the other recessive
• Genotype: genetic make up of individuals, alleles written in pairs
• Phenotype: physical expression of a trait
• (Mendel’s model). Pairs of genes segregate independently durihg gamete formation
• (Mendel’s model) independent assortment:

  • Pairs of genes, assort independently from other pairs of during gamete formation
  • All possible combinations form with equal frequency
• Heritable feature that varies among individuals is called a character. Example is flower color.
• Each variant for a character such as purple or white color for flowers is called a trait
• plants that produce offspring of the same variety when they self pollinate are true breeding.
• The mating of two contrasting, true breeding varieties is called a hybridization
• True, breeding parents are the p generation
• The hybrid offspring of the pi generation are called the F1 generation and their offspring. When they self pollinate or cross pollinate will be the F2 generation.
• Punnet Square:

  • Reginald Punnett devised approach
  • Genotypes, infinite types, resulting from combining genes can be visualized
  • Display all possible random fertilization events
• Chi- Square analysis: evaluates influence of chance on genetic data
• Chance deviation: chance, events are subject to random fluctuations
• Alleles: alternative form of a gene
• Mutation: ultimate source of alleles

  • New phenotype result from changes in functional activity of gene product
  • Eliminating enzyme function
  • Changing relative enzyme, efficiency
  • Changing overall enzyme function
• Wild type (Wt) allele: occurs most frequently in nature, and is usually but not always dominant
• Loss of function mutation: a new phenotype results from change in activity. Mutation causes loss of wild type function.
• Gain of function mutations: mutation, enhances function of wild type. Quality of gene product increases.
• Neutral mutations: no change to phenotype, and no change to the evolutionary fitness of the organism
• Dominant alleles are written as italic, uppercase letter (D) or letters (Wr)
• recessive alleles are indicated by either an italic lowercase letter (d) or an italic group of letters (wr)
• Mutant alleles are indicated by an italic letter (e) or group of letters (wr)
• wild type alleles are indicated by italic letter or group of letters plus a superscript (e^+)
• With no true dominance exist, italic uppercase letters and superscripts are used or no alternative genes
• The exceptions to Mendel‘s complete dominant/recessive genotypes rule are incomplete or partial dominance, co-dominance, and multiple alleles in a population