[BIO] mendelian genetics

• chromosomes


  threadlike structure made up of a DNA molecule wrapped around proteins & stores genomic information
• genes


   section of DNA that codes for a specific function or protein & is made up of nucleotides
• alleles


  • variations of a gene that allow for differences between individuals
  • results of gene mutations
• difference between alleles and genes

  genes create the individual, while alleles allow for the differences between the individuals
• locus


  location of the gene on a chromosome
• karyotype


  micrograph of an individual's chromosome pairs
• total number of pairs in a karyotype

  23
• pairs 1-22 (karyotype)


  autosomes
• autosomes


  any non-sex chromosomes
• pair 23 (karyotype)


  sex chromosomes (XX: female, XY: male)
• homozygous


  same alleles
• heterozygous 


  different alleles
• homozygous dominant genotype


  AA (both uppercase)
• genome 


  all of the genetic material in an organism's cells
• homozygous recessive genotype


  aa (both lowercase)
• heterozygous hybrid genotype 


  Aa (one upper, one lower)
• monohybrid cross

  • cross between two parents with homozygous genotypes
  • AA x aa
  • results in all heterozygous offspring
• dihybrid cross

  • cross between individuals that are both heterozygous for 2 traits
  • phenotypic ratio: 9:3:3:1

  
• gregor mendel

  • father of modern genetics due to his experiments on pea plants
  • did his work in St. Thomas Abbey
  • observed passing down of traits and interactions between alleles
• why did gregor mendel use pea plants?

  • easily grown
  • can be cross-pollinated
  • they have contrasting characteristics
• mendel's laws of inheritance (3)

  1. law of dominance
  2. law of segregation
  3. law of independent assortment
• law of dominance


  the dominant allele will always be the one expressed as long as it is present in the genotype
• law of segregation


  • for a specific gene, only 1 allele from each parent is inherited by an organism.
  • the alleles for a gene segregate during gamete formation
  • allocation of alleles is done randomly
  • seen in the monohybrid cross because this only deals with a single gene set
• law of independent assortment


  • there is no fixed pattern for the alignment of the chromosomes on the metaphase plate
  • genes for the different traits assort independent of each other during meiosis
  • seen in the dihybrid cross because this is better understood when studying more than 1 characters studied at a time
• sex chromosomes


  determines the sex
• homologous pair

  • pair of chromosomes that look alike and have the same gene sequence
  • may differ in their alleles
  • one homologous chromosome per parent

  
• true breeding

  • breeding wherein parents would produce offspring with the same phenotype
  • the parents are homozygous for every trait
  • the parents have identical genotypes
  • self-fertilization
• hybrid breeding

  • crossing parents that have different genotypes
  • at least one genotype of either parent is heterozygous
  • cross-fertilization
• possible reasons for recessive alleles being masked?

  • there is a dominant allele
  • even when there are 2 recessive alleles, the presence of a non-functional protein alters the phenotype
• wild type allele/genotype/phenotype


  most common expression of a gene in a population
• mutant allele/genotype/phenotype


  comes from a gene that underwent mutation
• test cross


  mating between a homozygous recessive individual and an individual with an unknown genotype in order to know the unknown
• Genomic


  Refers to the complete genetic material of an organism, including all of its genes and the non-coding regions of DNA. It encompasses the entire genetic makeup of an organism.
• Genetic


  Refers to anything related to genes or heredity. It can refer to a specific gene or a characteristic determined by genes.