Genetics

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)

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.  B.C.: horses, camels, oxen, dogs.  5000 B.C.: maize (corn) wheat, rice, date palm.

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 ( ) and others clearly disproved this ideal.  During same time: atomic theory and cell theory were being developed.

Homunculus

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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.

General Animal Cell Location of genetic material: DNA

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

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.

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

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

Chromosome (coiled chromatin) Chromatin Only visible during cell division

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.

Genetic material for all life on planet Earth (Nucleic acid: DNA double helix)

Questions?