General Biology 2

• Gregor Mendel


  Father of Genetics
• Gregor Mendel


  • First biologist to use Mathematics to explain his results quantitatively
• Principle of Dominance and Recessiveness


  When pure parents with opposite traits are mated, the first generation shows only one trait (dominant), while the other trait (recessive) is hidden
• Principle of Segregation


  When gametes are formed, the pairs of hereditary factors (genes) become separated, so that each sex cell (egg/sperm) receives only one kind of gene
• Principle of Independent Assortment


  Members of one gene pair segregate independently from other gene pairs during gamete formation. Gives 9:3:3:1 ratio in F2 cross of heterozygous individuals
• Patterns of Inheritance


  The manner in which a particular genetic trait or disorder is passed from one generation to the next
• Pedigree


  Chart of the genetic history of family over several generations
• GENETICS - branch of biology that deals withheredity and variation of organisms
• Chromosomes - carry the hereditary information (genes)
• Homologous Chromosomes - Chromosomes (and genes) occur in pairs
• • New combinations of gones occur in sexual reproduction
• Gene - a unit of heredity a section of DNA sequence encoding a single protein
• Genome - the entire set of genes in an organism
• Alleles - two genes that occupy the same position on homologous chromosomes and that cover the same trait (like flavors of a trait)
• Locus - a fixed location on a strand of DNA where a gene or one of its alleles is located.
• • Homozygous - having identical genes (one from each parent) for a particular characteristic
• • Heterozygous - having two different genes for a particular characteristic
• • Dominant - the allele of a gene that masks or suppresses the expression of an alternate allele, the trait appears in the heterozygous condition
• • Recessive - an allele that is masked by a dominant allele, does not appear in the heterozygous condition, only in homozygous.
• • Genotype - the genetic makeup of an organisms
  • Phenotype - the physical appearance of an organism (Genotype + environment)
• Monohybrid cross: a genetic cross involving a single pair of genes (one trait), parents differ by a single trait.
• dihybrid cross - a mating experiment between two organisms that are identically hybrid for two traits
• • P = Parental generation
  • F1 = First filial generation, offspring from a geneticCrosS
  • F2 = Second filial generation of a genetic cross
• Incomplete Dominance - This principle states that a cross between homozygous dominant and recessive genes will result to a progeny of heterozygous genes determining an intermediate trait between the dominant trait and recessive trait

  Both alleles exert an effect and jointly produce an Intermediate phenotype.
• Codominance - A form of dominance wherein two alleles are equally strong and are both visible in the hybrid.

  Example. A red hair coat cow is mated with white hair coat cow. The offspring of this cross produced roan cows where both red hair and white hair appear interspersed with each other as color coat of the resulting cows.
• Multiple Alleles - Type of non-Mendelian inheritance that involves more than two alleles. Multiple alleles exist when there are many

  variations. An example of these is the human blood
• Blocked Traits - A modifier gene controls another gene.

  Not dominant, because it Is not on the same gene, but will still override whatever gene it is the modifier for.

  Regulator genes can either Initiate or block the expression of other genes. They control the production of a variety of chemicals in plants and animals.
• Polygenetic Traits - Most traits in humans are not controlled by only 1 gene. There are many genes that contribute to a single trait
• Sex-Linked Traits - Trait that is controlled by a gene or an allele located in the sex chromosomes
• Sex-influenced Traits - trait controlled by a pair of alleles found on the autosomal chromosomes but its phenotypic

  expression is influenced by the presence of certain hormones

  eg estrogen, progesterone, testosterone, etc
• Sex-influenced Traits - Can be seen in both sexes, but will vary in frequency between the sexes, or in degree of phenotypic expression.
• Sex-limited Traits - Traits are expressed only in one gender.