Life Science Genetics

The study of heredity started with the work of Gregor Mendel and his pea plant garden Mendel was an Austrian Monk that lived in the mid 1800’s

Mendel noted that the size of pea plants varied Mendel noted that the size of pea plants varied. He cross-bred these pea plants to find some surprising results.

Mendel’s cross between tall pea plants yielded all tall pea plants Mendel’s cross between tall pea plants yielded all tall pea plants. His cross between small pea plants yielded all small pea plants. X = X = Mendels’ cross between tall pea plants and small pea plants yielded all tall pea plants. x =

Mendel then crossed these second generation tall pea plants and ended up with 1 out 4 being small. x =

Mendel’s work led him to the understanding that traits such as plant height are carried in pairs of information not by single sets of information. -Carrying the information are chromosomes. -Chromosomes are made up of sections called genes. -Genes are made up of DNA

DNA D.N.A. - Deoxyribonucleic Acid Molecule made of: 1. Deoxy Sugar 2. Combination of four nitrogen bases Either: a. Guanine b. Cytocine c. Thymine d. Adenine The sum total of combinations that these four bases are capable of creating are greater than all the stars visible in the night time sky

DNA Nitrogen bases pair up Pairing creates a ladder shape Cytosine & Guanine Thymine & Adenine Pairing creates a ladder shape Angle of bonds creates a twist Ladder and Twist produces the famous “Double Helix”

DNA DNA resides in all cells Each strand forms a chromosome Nucleus Cell DNA resides in all cells Inside the nucleus Each strand forms a chromosome DNA

DNA DNA is found in all living cells It controls all functions inside a cell It stores all the genetic information for an entire living organism Single cell like an amoeba Multi cell like a human

Genetics Small sections of DNA are responsible for a “trait”. These small sections are called “Genes”. Gene - A segment of DNA that codes for a specific trait Trait - A characteristic an organism can pass on to its offspring through DNA Gene

Genetics There are three basic kinds of genes: Dominant - A gene that is always expressed and hides others Recessive - A gene that is only expressed when a dominant gene isn’t present Codominant - Genes that work together to produce a third trait

Genetics So, back to the original question. What color hair will the offspring of Prince Charming and Snow White have?

Co-dominance Hair color is different from widows peak, no color is truly dominant. Brown and blond are the two, true traits Homozygous conditions produce either brown or blond hair Heterozygous conditions produce red hair

Genetics For Snow White to have brown hair she must be homozygous dominant, “BB”, a blond Prince Charmin must be homozygous recessive, “bb”. All the offspring from Prince Charming and Snow White will therefore be heterozygous, “Bb”, and since hair color is co-dominant….. all their children will have red hair B B b Bb Bb b Bb Bb