GeneticsGenetics

BACKGROUNDBACKGROUND

Genetics is the branch of biology that deals with Genetics is the branch of biology that deals with heredity and the expression of inherited traits.heredity and the expression of inherited traits.

Charles Darwin did not know anything about Charles Darwin did not know anything about how traits (like flower color) where passed-on how traits (like flower color) where passed-on from parent to offspring.from parent to offspring.

But that did not stop Darwin from studying But that did not stop Darwin from studying change through time of species. (evolution)change through time of species. (evolution)

Background cont.Background cont.

Ironically, Mendel was working on the very mechanism Ironically, Mendel was working on the very mechanism that would have greatly supported Darwin's theories.that would have greatly supported Darwin's theories.

But what neither one knew about - nor anyone until the But what neither one knew about - nor anyone until the early 20th century (1900's) was the mechanism of early 20th century (1900's) was the mechanism of inheritance.inheritance.

While we don't know when people first recognized the While we don't know when people first recognized the existence of heredity, there is evidence that suggests the existence of heredity, there is evidence that suggests the successful domestication of animals and cultivation of successful domestication of animals and cultivation of plants thousands of years ago.plants thousands of years ago.

8000-1000 B.C.: horses, camels, oxen, dogs. 8000-1000 B.C.: horses, camels, oxen, dogs. 5000 B.C.: maize (corn) wheat, rice, date palm.5000 B.C.: maize (corn) wheat, rice, date palm.

Background cont.Background cont.

Preformation: a theory first put forward in the Preformation: a theory first put forward in the 17th century (1600's). Stating that sex cells 17th century (1600's). Stating that sex cells contain a complete miniature adult called a contain a complete miniature adult called a homunculushomunculus

This theory was popular well into the 18th This theory was popular well into the 18th century (1700's).Later scientific discoveries by century (1700's).Later scientific discoveries by Casper Wolff (1733-1794) and others clearly Casper Wolff (1733-1794) and others clearly disproved this ideal.disproved this ideal.

During same time: atomic theory and cell theory During same time: atomic theory and cell theory were being developed.were being developed.

HomunculusHomunculus

CONCEPTSCONCEPTS What's the center of heredity in a cell? What's the center of heredity in a cell? In eukaryotic organisms it is the nucleus, in In eukaryotic organisms it is the nucleus, in

prokaryotes it is the nucleoid region.prokaryotes it is the nucleoid region. What is the genetic material?What is the genetic material? In eukaryotes & prokaryotes it is DNA, in viruses In eukaryotes & prokaryotes it is DNA, in viruses

it can be either DNA or RNA.it can be either DNA or RNA. What do DNA & RNA stand for? What do DNA & RNA stand for? DNA: deoxyribonucleic acid / RNA: ribonucleic DNA: deoxyribonucleic acid / RNA: ribonucleic

acid.acid. How is DNA organized to serve as the genetic How is DNA organized to serve as the genetic

material?material? DNA, although single-stranded in a few viruses, DNA, although single-stranded in a few viruses,

is usually a double-stranded molecule organized is usually a double-stranded molecule organized as a double helix.as a double helix.

General Animal CellGeneral Animal Cell

Location of genetic material: DNA

General Bacteria Cell (prokaryote)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.Concepts cont.

Contained within each DNA molecule are Contained within each DNA molecule are hereditary units called genes, which are hereditary units called genes, which are part of larger elements, the chromosomes.part of larger elements, the chromosomes.

What is a gene? The functional unit of What is a gene? The functional unit of heredity. heredity.

A segment of the DNA molecule that A segment of the DNA molecule that codes for a characteristic/trait.codes for a characteristic/trait.

There are many genes in a chromosome.There are many genes in a chromosome.

CENTRAL DOGMA OF GENETICSCENTRAL DOGMA OF GENETICS

Expression of the stored genetic Expression of the stored genetic information is a complex process.information is a complex process.

DNA DNA transcription transcription mRNA mRNA ribosomes ribosomes translation translation PROTEIN PROTEIN

Proteins were 1st thought to be the Proteins were 1st thought to be the genetic material for hereditary traits.genetic material for hereditary traits.

Later research pointed to nucleic acids Later research pointed to nucleic acids (DNA) Frederick Griffith ~ Medical officer (DNA) Frederick Griffith ~ Medical officer in the British Ministry of Health.in the British Ministry of Health.

MOLECULAR STRUCTUREMOLECULAR STRUCTURE

DNA is a chemical strand made-up of repeating DNA is a chemical strand made-up of repeating nucleotides.nucleotides.

Nucleotides are the building blocks of nucleic acids - Nucleotides are the building blocks of nucleic acids - DNA/RNA.DNA/RNA.

These units are made-up of 3 parts: a nitrogenous base, These units are made-up of 3 parts: a nitrogenous base, a pentose sugar (5-carbon sugar), and a phosphate a pentose sugar (5-carbon sugar), and a phosphate group. group.

There are 2 kinds of nitrogenous bases: purines & There are 2 kinds of nitrogenous bases: purines & pyrimidinespyrimidines

In nucleic acids, the purines are ADENINE & GUANINE, In nucleic acids, the purines are ADENINE & GUANINE, the pyrimidines are CYTOSINE, THYMINE, & URACILthe pyrimidines are CYTOSINE, THYMINE, & URACIL

MOLECULAR STRUCTURE cont.MOLECULAR STRUCTURE cont.

These chemicals are arranged into double-stranded These chemicals are arranged into double-stranded helixes.helixes.

This helix is referred to as chromatin during interphase of This helix is referred to as chromatin during interphase of the cell cyce & as chromosomes during mitosis and the cell cyce & as chromosomes during mitosis and meiosis.meiosis.

In the double helix, complemetary strands match-up in a In the double helix, complemetary strands match-up in a specific way.specific way.

Think of it as a latter that got sawed down the middle.Think of it as a latter that got sawed down the middle. When you put it together again, each step connects to a When you put it together again, each step connects to a

step on the other side.step on the other side. In DNA, it is as follows: A - T and G - C / in RNA T is In DNA, it is as follows: A - T and G - C / in RNA T is

replaced by U.replaced by U.

Questions?Questions?