History and Levels of Genetics

### History of Genetics

• Humans have known about inheritance for a long time.
• In 1926, Hermann J. Muller showed that X-rays induce mutations.
• Gregor Mendel, an Austrian monk, was born in 1822 in the Czech Republic.
• Mendel worked at the monastery and taught high school.
• He tended the monastery garden and became interested in the traits that were expressed in different generations of peas.

Levels of Genetics and Genomics

• Molecular
• Cellular
• Tissues
• Organs
• Individuals
• Families
• Population
• Evolution of Species

What is Genetics?

• It is the study of inherited traits and their variation.
• Certain difficult-to-define human characteristics might appear to be inherited if they affect several family members but may reflect shared genetic and environmental influences.

Genetic Information

• Genome: The complete set of genetic instructions.
• The human genome was completed in 2003, after starting in 1990.
• Genomics: Field that analyzes and compares genomes of different species

The Human Genome Project

• 1990 - 2003
• The human genome underlies the fundamental unity of all members of the human family, as well as their inherent dignity and diversity.

Genes and Dominance

• Mendel studied seven different pea plant traits.
• Each trait had a contrasting form.
• Recessive: Wrinkled
• Dominant: Round
• Recessive: Constricted
• Dominant: Inflated
• Recessive: Yellow
• Dominant: Green
• Recessive: Yellow
• Dominant: Green

### Segregation

• Mendel wanted to answer the question: Had the recessive alleles disappeared or were they still present in the F1 plants?
• To answer this question, he allowed the F1 plants to produce an F2 generation by self-pollination.

The F1 Cross

• The recessive traits reappeared! Roughly 1/4 of the F2 plants showed a recessive trait.

### Punnett Square

• A diagram used to determine genetic crosses.
• Named after Reginald C. Punnett.
• A way of visualizing various crosses.
• It aids in problem-solving.
• The square represents all possible random fertilization events.

### Chromosome Staining and Banding

• A chromosome band is a part of a chromosome that is clearly distinguishable from its adjacent segments comprised of alternating light and dark stripes.
• G-Banding: A photographic representation of a stained metaphase spread in which the chromosomes are arranged in order of decreasing length.
• C-Banding: DNA is selectively depurinated and denatured by barium hydroxide, and the fragments are washed away by incubation in a warm salt solution.
• T-Banding: A harsher treatment of the chromosomes diminishes staining except at the heat-resistant telomeres.
• NOR Staining: Nucleolar organizer regions (NORs) located on the satellite stalks of the acrocentric chromosomes.

Gel Electrophoresis

• A method of separating electrically charged substances in a mixture
• Gel material acts as a "molecular sieve.”
• The technique is widely used for separating proteins and nucleic acids.
• General Principle: Each charged substance migrates toward the cathode or the anode at a speed that depends on its net charge, size, and shape.
• When an electrical field is applied to a solution, solute molecules with a net positive charge migrate toward the cathode, and molecules with a net negative charge move toward the anode.

### Whole Genome Sequencing

• Involves finding out the whole sequence of a person's DNA.
• A laboratory procedure that determines the order of bases in the genome of an organism in one process.

### Significant Events

• 1952: Alfred Hershey and Martha Chase conducted the "blender experiment", demonstrating that phage DNA enters the cell and leads to its rupture. This experiment is often mistakenly considered the definitive proof that DNA is the genetic material.
• 1953: James Watson and Francis Crick presented a structural model of DNA, suggesting that it consists of two anti-parallel chains held together by hydrogen bonds. This model suggested a method for DNA replication.
• 1957: Francis Crick proposed the central dogma of molecular biology, elucidating the link between DNA, RNA, and protein synthesis.
• 2001: The International Human Genome Sequencing Consortium and Celera Corp published the human genome sequence (2900 Mbp). The genome was estimated to contain between 35,000 and 40,000 genes, later revised to approximately 30,000 genes.
• 2002: The Mosquito Sequencing Consortium published the genome sequence of the malaria-parasite-carrying mosquito (278 Mbp). The genome was shown to contain 13,600 genes, similar to the number found in Drosophila.
• 2003: The British Columbia Cancer Agency released the SARS-associated coronavirus genome sequence (30 Kbp). The genome contains 16 open-reading frames. The sequence was released less than five months after the disease began spreading worldwide.

Explore the fascinating journey of genetics from Mendel's initial discoveries to modern genomic science. Understand different levels of genetics including molecular, cellular, and population genetics. This quiz will test your knowledge on key historical figures and concepts in genetics.