Genetics/Inheritence

• Gregor Mendall


  Father of genetics
• Mendell's laws


  • Law of dominance
  • Law of segregation
• Law of dominance


  One allele for a trait will mask the alternate allele
• Law of segregation


  Each individual has two alleles for a trait, alleles segregate separately when making gametes, each gamete has one allele for a trait, fertilization gives each new individual two alleles for a trait
• Genes


  Sections of chromosomes coded by a sequence of nucleotides which are the instructions to build an organism, genes code for traits
• Locus


  Position where the gene is found on the chromosome
• Phenotype


  Physical characteristic expressed by the gene, e.g. eye colour, hair colour, enzyme active or inactive
• Alleles


  Alternative forms of a gene that control the phenotype
• Genotype


  Shorthand way of describing a gene and its alleles, indicated by two letters
• Dominant trait


  Overpowering, hides the second trait, represented by a capital letter
• Recessive trait


  Hidden allele, represented by a lowercase letter
• Homozygous


  Both alleles are identical (can be dominant or recessive)
• Heterozygous


  Both alleles are different (1 dominant, 1 recessive)
• At the end of Meiosis

  gametes have only 1 allele for a trait
• Fertilization


  Gives offspring 2 alleles for a trait
• Punnett Square


  • Determines the genotype and phenotypes of the offspring
• The dominant color masks the recessive color and all offspring are carriers of the recessive gene
• Carriers have the gene but don't show it in the phenotype
• 1. linked or sex-linked disorders

  only males have the disorder, rare for females to have it
• Autosomal chromosomes are 1-22, X or Y are sex chromosomes
• The sex of the baby is determined by the X or Y chromosome
• 1. linked disorders like hemophilia, muscular dystrophy, and color blindness are recessive</b>
• Law of independent assortment


  1. Each pair of traits segregate independently of other pairs, 2) All possible allele combinations occur in the gametes
• Widow's peak, detached earlobes

  • Possible genotypes and phenotypes
• The classic Mendelian 9:3:3:1 dihybrid ratio
• DNA


  Controls the production of proteins via the genetic code, found in the nucleus
• Transcription


  DNA code is transcribed into mRNA in the nucleus
• mRNA


  Messenger RNA, carries the DNA code to the cytoplasm for protein synthesis
• Translation


  Genetic code language (nucleotide alphabet) is translated into the language of protein (amino acid alphabet)
• Ribosome


  Translates the mRNA to make a polypeptide
• tRNA


  Transfer RNA brings amino acids to the mRNA-ribosome complex
• Protein synthesis


  Initiation: Ribosome binds to mRNA, 2) Elongation: Ribosome moves along mRNA adding amino acids, 3) Termination: Ribosome reaches stop codon and releases polypeptide
• Polypeptide


  Linear chain of amino acids, needs to be folded into 3D shape to be functional
• Gene mutation


  Change in the nucleotide sequence of a gene
• Types of gene mutations

  • Frameshift
  • Point mutation
  • Expansion mutation
• Frameshift mutation


  Deletion or insertion of a base, results in a non-functioning protein
• Point mutation


  One base within a codon is changed to another, can be silent, missense, or nonsense
• Expansion mutation


  Repeating sequence of nucleotides, up to 100 times
• DNA


  Controls the production of proteins via the genetic code
• Genetic code


  Series of nucleotide bases that code for the genes