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Understanding Genetics: Heredity, DNA, and Protein Synthesis

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  1. Genetics

  2. BACKGROUND • Genetics is the branch of biology that deals with heredity and the expression of inherited traits. • Charles Darwin did not know anything about how traits (like flower color) where passed-on from parent to offspring. • But that did not stop Darwin from studying change through time of species. (evolution)

  3. Background cont. • Ironically, Mendel was working on the very mechanism that would have greatly supported Darwin's theories. • But what neither one knew about - nor anyone until the early 20th century (1900's) was the mechanism of inheritance. • While we don't know when people first recognized the existence of heredity, there is evidence that suggests the successful domestication of animals and cultivation of plants thousands of years ago. • 8000-1000 B.C.: horses, camels, oxen, dogs. • 5000 B.C.: maize (corn) wheat, rice, date palm.

  4. Background cont. • Preformation: a theory first put forward in the 17th century (1600's). Stating that sex cells contain a complete miniature adult called a homunculus • This theory was popular well into the 18th century (1700's).Later scientific discoveries by Casper Wolff (1733-1794) and others clearly disproved this ideal. • During same time: atomic theory and cell theory were being developed.

  5. Homunculus

  6. CONCEPTS • What's the center of heredity in a cell? • In eukaryotic organisms it is the nucleus, in prokaryotes it is the nucleoid region. • What is the genetic material? • In eukaryotes & prokaryotes it is DNA, in viruses it can be either DNA or RNA. • What do DNA & RNA stand for? • DNA: deoxyribonucleic acid / RNA: ribonucleic acid. • How is DNA organized to serve as the genetic material? • DNA, although single-stranded in a few viruses, is usually a double-stranded molecule organized as a double helix.

  7. General Animal Cell Location of genetic material: DNA

  8. General Bacteria Cell (prokaryote) In bacteria, since they don’t have a nucleus, the DNA is found in an area called thenucleoid region

  9. Concepts cont. • Contained within each DNA molecule are hereditary units called genes, which are part of larger elements, the chromosomes. • What is a gene? The functional unit of heredity. • A segment of the DNA molecule that codes for a characteristic/trait. • There are many genes in a chromosome.

  10. CENTRAL DOGMA OF GENETICS • Expression of the stored genetic information is a complex process. • DNA  transcription  mRNA  ribosomes  translation  PROTEIN • Proteins were 1st thought to be the genetic material for hereditary traits. • Later research pointed to nucleic acids (DNA) Frederick Griffith ~ Medical officer in the British Ministry of Health.

  11. MOLECULAR STRUCTURE • DNA is a chemical strand made-up of repeating nucleotides. • Nucleotides are the building blocks of nucleic acids - DNA/RNA. • These units are made-up of 3 parts: a nitrogenous base, a pentose sugar (5-carbon sugar), and a phosphate group. • There are 2 kinds of nitrogenous bases: purines & pyrimidines • In nucleic acids, the purines are ADENINE & GUANINE, the pyrimidines are CYTOSINE, THYMINE, & URACIL

  12. MOLECULAR STRUCTURE cont. • These chemicals are arranged into double-stranded helixes. • This helix is referred to as chromatin during interphase of the cell cyce & as chromosomes during mitosis and meiosis. • In the double helix, complemetary strands match-up in a specific way. • Think of it as a latter that got sawed down the middle. • When you put it together again, each step connects to a step on the other side. • In DNA, it is as follows: A - T and G - C / in RNA T is replaced by U.

  13. Questions?

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