Genetics Insert awwwss

History of Genetics Trait: A variation of a particular character. In the early 1800s, the common thought on genetics was called the blending theory. This is when two traits would mix to form a variation of both of them. Ex:

Blending Process All offspring of the orange flowered plants would also have orange flowers. There were too many exceptions to this though. Some times red flowers would randomly produce yellow flowers. The blending process was discarded because it could not account for traits that were not present in one generation but present in another.

My Main Man Mendel Gregor Mendel: was one of the first biologists to apply an experimental approach to the question of inheritance. His work eventually gave rise to genetics. Genetics: the study of heredity. I just humor Mr. O’D

Mendel’s Work For years, Mendel worked with pea plants to figure out if there was a pattern to which traits were handed down to their offspring. Why pea plants? Based upon his results, he came up with the particulate hypothesis. This stated that parents pass on to their offspring separate and distinct factors (genes) that are responsible for inherited traits.

Why pea plants? - they were easy to grow -they grew fast -their traits are easy to identify -they have different traits that can be easily observed -they have different types that can be easily combined -convenient convenient

Heritable Traits - Mendel stressed that these genes (not called them at the time) retain their identity generation after generation. - to test this, Mendel first identified pea plants that were true-breeding. - When, self-fertilized, a true-breeding plant produces offspring identical in appearance to itself generation after generation.

Cross-Fertilization - to test his particulate hypothesis, Mendel crossed true-breeding plants that had two distinct and contrasting traits. - in a method called cross-fertilization, sperm from the pollen of one flower fertilizes the eggs in the flower of a different plant. - the fertilized eggs developed into embryos within seeds (peas) that Mendel planted.

Mendel’s Principle of Segregation The offspring of two different true- breeding varieties are called hybrids. The parental plants are called P- Generation (parental) and the hybrid offspring at the F 1- Generation (filial, or Latin for son). When the F 1 plants self-fertilize or fertilize each other, their offspring are the F 2 Generation.

Mendel’s Principle of Segregation Mendel crossed purple-flowered pea plants with white-flowered pea plants. Monohybrid Cross: A pairing in which the parent plants differ in only one (mono) character. F 1 there were only purple-flowers. F 2 ¾ of the plants were purple and ¼ plants were white. In conclusion, there was something in the F 1 that allowed the offspring to have both characteristics.

Mendel’s Principle of Segregation

From this Mendel developed four hypotheses: 1.There are alternative forms of genes called alleles. (one purple flower one white flower) 3 Character Differences Between Mr. O’D and His Brother

2.) For each inherited character, an organism has two alleles for the gene controlling the character, one from each parent. If the two alleles are the same, the individual is homozygous for that character. If the two alleles are different, the individual is heterozygous.

3.) When only one of the two different alleles in a heterozygous individual appears to affect the trait, that allele is called dominant. If it does not appear to affect the trait, it is recessive. Capital letters = dominant Lower case letters = recessive

3 Character Differences Between Mr. O’D and His Brother

4.) the two alleles for a character segregate during the formation of gametes, so that each gamete carries only one allele for each character. This is known as the Principle of Segregation. The union of gametes during fertilization reforms allele pairs in the offspring.

Probability and Punnett Squares Punnett Square: A type of diagram that shows all possible outcomes of a genetic cross. Heterozygous: Pp Homozygous: pp or PP

Genotype and Phenotype Phenotype: An observable trait. Genotype: the genetic makeup, or combination of alleles (PP).

Trait:

Principle of Independent Assortment Dihybrid cross: Crossing organisms differing in two characters. Mendel crossed a true-breeding plant grown from a round yellow seed (RRYY) with a true-breeding plant grown from a wrinkled seed (rryy).