Genetics BACKGROUND Genetics is the branch of biology

Genetics

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

Background cont. Ø Ø Ø 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 20 th 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.

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

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. Ø What is the genetic material? Ø In eukaryotes & prokaryotes it is DNA, in viruses it can be either DNA or RNA. Ø What do DNA & RNA stand for? Ø DNA: deoxyribonucleic acid / RNA: ribonucleic acid. Ø How is DNA organized to serve as the genetic material? Ø DNA, although single-stranded in a few viruses, is usually a double-stranded molecule organized as a double helix. Ø Ø

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

CENTRAL DOGMA OF GENETICS Ø Expression of the stored genetic information is a complex process. Ø DNA transcription m. RNA ribosomes translation PROTEIN Ø Proteins were 1 st thought to be the genetic material for hereditary traits. Ø 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. Ø Nucleotides are the building blocks of nucleic acids - DNA/RNA. Ø These units are made-up of 3 parts: a nitrogenous base, a pentose sugar (5 carbon sugar), and a phosphate group. Ø There are 2 kinds of nitrogenous bases: purines & pyrimidines Ø In nucleic acids, the purines are ADENINE & GUANINE, the pyrimidines are CYTOSINE, THYMINE, & URACIL Ø

Only visible during cell division Chromosome (coiled chromatin) Chromatin

MOLECULAR STRUCTURE cont. Ø Ø Ø 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)

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