genetics

• Inheritance


  The process by which genetic information is passed from parents to offspring
• DNA


  Genetic information is carried in the form of DNA, located in the chromosomes of the cell
• Chromosome


  Structures in the nucleus of a cell that contain DNA and genetic information
• Gene


  A length of DNA that codes for a protein
• Allele


  Different versions of the same gene
• Normal human cells have 23 pairs of chromosomes, known as diploid cells
• Sex chromosomes


  The pair of chromosomes that determines the sex or gender of an individual
• Male sex chromosomes


  • One X and one Y chromosome
• Female sex chromosomes


  • Two X chromosomes
• Fertilization

  1. Sperm with X chromosome fertilizes egg

  2. Sperm with Y chromosome fertilizes egg
• DNA


  Provides instructions for making proteins in cells
• Protein synthesis


  1. DNA transcription

  2. mRNA translation
• Most body cells contain the same genes, but not all genes are expressed in every cell
• Haploid nucleus


  Nucleus containing a single set of chromosomes
• Diploid nucleus


  Nucleus containing two sets of chromosomes
• Mitosis


  • Nuclear division giving rise to genetically identical cells
  • Involved in growth, repair, and asexual reproduction
• Meiosis


  • Nuclear division resulting in genetically different haploid cells
  • Involved in the production of gametes
• Inheritance


  Transmission of genetic information from generation to generation
• Gene


  Section of DNA that provides instructions for making a specific protein which influences a particular characteristic
• Alleles


  Variations of the same gene
• Genotype


  Genetic makeup of an organism including all of its genes and alleles
• Phenotype


  Observable features of an organism
• Homozygous


  Having two identical alleles of a particular gene
• Heterozygous


  Having two different alleles of a particular gene
• Dominant allele


  Allele that is expressed if it is present in the genotype
• Recessive allele


  Allele that is only expressed when there is no dominant allele of the gene present in the genotype
• Monohybrid inheritance


  Study of how a single trait or characteristic is passed from parents to their offspring
• Punnett Square


  1. Determine the possible combinations of alleles in offspring

  2. Calculate the ratio of these combinations
• Eye color gene

  • Brown eye allele is dominant (capital B)
  • Blue eye allele is recessive (small b)
• Homozygous dominant parent crossed with homozygous recessive parent


  All offspring have brown eyes (heterozygous)
• Two heterozygous parents crossed


  Offspring have 75% chance of brown eyes, 25% chance of blue eyes
• Heterozygous parent crossed with homozygous recessive parent


  Offspring have 50% chance of brown eyes, 50% chance of blue eyes
• Test cross


  Cross unknown genotype with recessive phenotype to determine if homozygous or heterozygous
• Pedigree diagram


  Used to track how a specific trait or disease is passed through generations in a family
• Co-dominance


  Both alleles in heterozygous organisms contribute to the phenotype
• Blood group inheritance


  • Alleles I^a and I^b are co-dominant, both dominant over I^O
• Cross involving co-dominant alleles

  Possible offspring genotypes: I^a I^b, I^a I^O, I^b I^O, I^O I^O
• Sex-linked characteristic


  Feature in which the gene responsible is located on a sex chromosome
• Red-green color blindness


  • Caused by mutation in genes on X chromosome, more common in males
• Normal male crossed with carrier female

  Possible offspring: normal female, carrier female, normal male, color blind male