Genetics

• Genetics - study of heredity, variation, and the molecular structure, function, and behavior of genes
• Genes - basic functional units of heredity composed of specific DNA sequences from its parent to offspring.
• Character - heritable feature that vary among individuals
• Traits - variations of a character
• Alleles - different versions of a gene that code for the same trait.
• Genome - entirely of an organism's hereditary information
• Genotype - genetic makeup of an individual
• Phenotype - observable characteristics of an individual
• Law of Dominance - 2 alleles differ; the dominant is fully expressed in the organism's appearance. While the recessive has no noticeable effect
• Law of Segregation - 2 alleles for each character segregate during gamete production or meiosis.
• Law of Independent Assortment - inheritance of 1 allele will not affect that of another. Probability of having a specific geno/phenotype depends only on the alleles of the parents.
• Monohybrid Cross - mating of 2 parent individuals, only concerned with one character/gene
• Genotypic Ratio - proportion of all the possible genotypes of offspring from a cross
• Phenotypic Ratio - proportion of all the possible phenotypes of offspring from a cross
• Dihybrid Cross - mating between 2 individuals with two observed traits that are controlled by two distinct genes
• Incomplete dominance - dominant allele is not completely expressed over recessive allele
• Codominance - no blending of traits, both alleles contribute to the apperance
• Multiple alleles - more than 2 possible traits
• Polygenic inheritance - 2 or more genes that exert their effects on a single phenotypic character
• Sex-linked: trait found in the sex chromosomes
• Sex-influenced: not governed by genes found in the sex chromosomes, but expression of dominance depends on the sex/gender of an individual
• Sex-limited: manifested only on 1 sex/gender because of physiology or anatomy
• Mutations

  • permanent changes in the genetic material of a cell
  • may occur naturally or induced by chemicals, radiation, ov light or heat.
  • important agents in introducing variation to organisms
• Gene Mutations - alteration in the nucleotide sequence of a gene
• Point mutations - occur when there is change in a single base in the DNA sequence
• Silent mutations - a mutation that does not change the amino acid sequence of the protein
• Missence mutation - single base substitution that encodes a different amino acid
• Nonsense mutation - a mutation that results in a stop codon being read and the protein is not produced
• Frame shift mutations - a mutation that changes the order of bases in a gene
• Chromosomal mutations - changes in the number or structure of chromosomes, usually yield more severe efects in the survival.