DEF. OF TERMS

• Fertilization, also known as conception, is the process by which sperm and ovum combine to create a single cell called zygote, which then duplicates itself by cell division
• Ovulation is the rupture of a mature follicle in either ovary and the expulsion of its ovum, which occurs every month until menopause
• Dizygotic Twins, also known as Fraternal Twins:

  • Result from two separate eggs being fertilized by two different sperms
  • Can be same or different sex
  • May have a genetic basis
• Monozygotic Twins result from the cleaving of one fertilized egg and are generally genetically identical
• Heredity is the genetic transmission of heritable characteristics from parents to offspring
• Deoxyribonucleic Acid (DNA) is a long, spiraling ladder whose steps are made of pairs of chemical units called bases:

  • Adenine
  • Thymine
  • Cytosine
  • Guanine
• Chromosomes are coils of DNA consisting of smaller segments called genes
• Mitosis is the cell division process of non-sex cells
• Meiosis is the cell division process of sex cells
• Mutation is a mistake in copying genetic code which creates a permanent alteration in genetic material
• Autosomes are not affiliated with sexual expression
• Sex Chromosomes, the 23rd pair, indicate the baby’s sex (XX for female, XY for male)
• Alleles produce alternative expressions of characteristics
• Homozygous refers to when two alleles are the same
• Heterozygous refers to when two alleles are different
• Dominant alleles are always expressed or show up as a trait in that person
• Recessive alleles usually don’t show unless paired with another recessive trait
• Polygenetic Inheritance involves the interaction of several genes
• Phenotype refers to observable characteristics
• Genotype is the underlying genetic makeup
• Epigenesis – environment can influence when and which genes turn on and off ▪ Refers to chemical molecules attached to a gene that alter the way a cell “reads” the gene’s DNA ▪ Cells are susceptible to epigenetic modification during critical periods such as puberty and pregnancy