2410B - Chapter 2

• Gene: A segment of DNA on the length of a chromosome
• Humans are 99.1% genetically identical
• Chromosome: thread like structures in the nucleus of the cell that contains genetic material
• Two types of Cells: Somatic and Sex Cells
• Somatic Cells: Cells that are not germ cells or gametes
• Sex Cells: reproductive cells each with 23 chromosomes. formed through meiosis
• Crossing Over: process in which genetic material is exchanged between pair of chromosomes during meiosis
• Biological sex is determined by the chromosome of the 23rd pair
• Supermale Syndrome (XYY): sex chromosome disorder in which there's an extra Y chromosome

  1. 1 in 1000 births
  2. taller than average, large teeth, prone to acne
  3. not associated with lower intelligence, increased aggression
• Klinefelter's syndrome (XXY or XXXY): sex chromosome disorder where a person has an extra X chromosome

  1. 1 in 750 Births
  2. Phenotypically male, but with some female secondary sex characteristics
  3. Impaired verbal ability
• Turner's syndrome (XO): sex chromosome disorder where a female is born with only one X chromosome

  1. 1 in 2500 female births
  2. Phenotypically female, but small in stature, underdeveloped
  3. sterile
  4. impaired spatial ability
• Poly-X or Superfemale Syndrome: sex chromosome disorder where a female is born with extra X chromosomes

  1. 1 in 1000
  2. Phenotypically female, normal in appearance
  3. Some intellectual deficits, esp. verbal
• Dominant Allele: the form of an allele whose chemical instructions are followed
• Recessive Allele: An allele whose instructions are ignored when combined with a dominant allele
• Trisomy: an extra copy of a chromosome
• Genotype: an individual's complete set of inherited traits
• Phenotype: directly observable characteristics
• Alleles: alternative versions of a gene that occupy the same position on homologous chromosomes
• Phenotype expressed through combinations of dominant and recessive alleles
• Homozygous: both alleles are the same (BB or bb)
• Heterozygous: Both alleles are different (Bb)
• What are the 2 Recessive Diseases?

  PKU (Phenylketonuria) and Cystic Fibrosis
• PKU: Phenylalanine, an amino acid, accumulates in the body and damages the nervous system, causing cognitive delay

  1. affects the body's ability to break down proteins
  2. dietary treatment must begin early
• Huntington's Disease: A type of dementia caused by a dominant allele; characterized by degeneration of the nervous system. chromosome 4
• Mutation: a sudden but permanent change in a segment of DNA
• Heritability: an estimate of the proportion of the trait variability in a population that is determined by genetic differences
• Sickle Cell Disease: a groups of inherited red blood cell disorders

  1. Homozygous Recessive
• Albinism: A condition in which the pigment melanin is absent from the skin, hair, and eyes
• Tay-Sachs Disease: The nervous system degenerates in infancy, causing blindness, deafness, cognitive delay, and death

  1. Homozygous Recessive
• Hemophilia: A disorder in which the blood does not clot properly.

  1. Recessive
• Down Syndrome: A disorder caused by an extra 21st chromosome, that result in intellectual disability and a distinctive appearance
• Twin Studies

  1. Monozygotic: union of one egg and one sperm that splits in two, soon after conception
  2. Dizygotic: two different eggs fertilized by two different sperm
• Twin Studies

  1. Monozygotic: union of one egg and one sperm that splits in two, soon after conception
  2. Dizygotic: two different eggs fertilized by two different sperm