Genetics: the study of the traits.

Gregor Mendel is considered the Father of Modern Genetics because of his 1865 paper in which he proposed the following:

• Principle of dominance and recessiveness - one factor in a pair may mask the effect of the other.
   
• Principle of segregation - the two factors for a characteristic separate during the formation of eggs and sperm.
   
• Principle of independent assortment - The factors for different characteristics are distributed to reproductive cells independently.

Mendel's work was with seven characteristics of garden pea plants.

 
Important terms related to genetics:

• Mendelian genetics - inheritance patterns which can be explained by simple rules of dominance and recessiveness of genes.
   
• Genotype - the genetic makeup of an organism.
   
• Phenotype - the external appearance of an organism.
   
• Homozygous trait - the genes for that trait are the same.
   
• Heterozygous trait - the genes for that trait are not the same.
   
• Monohybrid cross - a cross between individuals with one pair of contrasting genes.
   
• Dihybrid cross - a cross between individuals with two pairs of contrasting genes.
   
• Parents - the two organisms whose genes produce offspring.
   
• F₁ generation - the offspring from parents.
   
• F₂ generation - the offspring produced by crossing two F₁ individuals.

 
To understand genetics, you must understand probability:

The combination of genes when gametes combine is a random event. The probabiliby of any event occuring is the fraction of outcomes in which that event occurs.

• A single roll of a dice has possible outcomes of 1, 2, 3, 4, 5, and 6.
   
• The probability of rolling a 5 is one out of 6 or ¹/₆.
   
• What is the probability of cutting the Ace of Spades from a deck of shuffled cards?

The Product Rule can be used to determine the probability of any two random events occuring at the same time. For instance, what is the probability of two dice coming up 5 at the same time? Since each dice has a ¹/₆ chance of being a 5, the probability that both dice would be 5 is,

CONCEPTS (continued)  

A Punnett square is a chart drawn to determine the probable results of a genetic cross.

• More about Punnett squares

 
A pedigree study produces a chart that traces the "history" of traits through several generations. These studies frequently identify the carrier of a trait - a person who has a single recessive gene but does not show the trait.

 
Heredity is the passing of traits from one generation to the next.

Many human traits are actually influenced by genes that have more than two alternative forms. These traits are called polygenic traits. Blood type is the classic example of a polygenic trait. There are three forms of the blood type gene, I^A, I^B, and i. An individual's blood type is determined by two of these genes.

Sex-linked traits have genes located on a sex chromosome. Genes on the X chromosome are X-linked and genes on the Y chromosome are Y-linked. When genes are X-linked, males are much more likely to show the recessive trait since there is no complementary gene on the Y chromosome. Color blindness and hemophilia are examples.

Sex-influenced traits are located on autosomes (body cells other than gametes), but express themselves differently in the sexes because of sex hormones. Pattern baldness is an example.
 
Recombinant DNA is a combination of DNA from two or more sources. One of the best applications of recombinant DNA today is the production of human insulin by bacteria cells.

Eugenics was a thriving science in the 1930's. A single person wiped out this whole science. Who was it?