HEREDITY: INHERITANCE AND VARIATIONS

• DNA - a nucleic acid that stores and transmits the genetic information from one generation of an organism to the next
• The building block of DNA is called nucleotides.
• Each nucleotide in DNA is composed of one phosphate group, the sugar deoxyribose, and one of the four bases Adenine, Thymine, Cytosine and Guanine
• RNA - a nucleic acid that differs in 3 ways to DNA:

  1. RNA is single stranded whereas DNA structure is double stranded
  2. The sugar in RNA is ribose, while DNA has deoxyribose
  3. Thymine is replaced with Uracil (U)
• The major types of RNA include:

  1. Messenger RNA
  2. Ribosomal RNA
  3. Transfer RNA
• Replication

  • DNA is copied during interphase prior to mitosis and meiosis

  • It is important that new copies are exactly like the original molecule

  • The structure of the DNA provides a mechanism for making accurate copies of the molecule
• Replication - the process of making copies of DNA
• When DNA replicates, two identical copies of DNA molecules are produced, which are exactly the same as the original.
• Events while DNA copies itself:

  1. An enzyme called helicase breaks the bond between nitrogenous bases. The two strands of DNA splits.
  2. The base attached to each strand then pair up with the free nucleotides found in the cytoplasm.
  3. The complementary nucleotides are added to each strand by DNA polymerase to form new strands. Two new DNA molecules, each with a parent strand and each with a new strand are formed.
• The DNA replication is known as semi-conservative replication because one of the old strands is conservative replication of DNA.
• 3 major types of RNA that helps in the building of protein:

  1. Messenger RNA - brings information from the DNA in the nucleus to the protein manufacturing are, the cytoplasm. In the cytoplasm, the mRNA becomes the template of information to make proteins.
  2. Ribosomal RNA - holds tightly into the mRNA using its information to assemble the amino acids in correct order.
  3. Transfer RNA - supplies amino acids to the ribosome to be assembled as protein.