Genetics Page 114-132

Gregor Mendel Heredity- passing of traits from parent to offspring Gregor Mendel is considered to be the “Father of Genetics” He worked with pea plants to determine the patterns of inheritance

Why did he use pea plants? Self-pollinating plants have both male and female reproductive structures. The pollen from one flower can fertilize the ovule of the same flower or another flower True-breeding plants self-pollinate therefore all the offspring will have the same traits as the parent. Cross-pollination- pollen from one plant fertilizes the ovule of a flower on another plant.

Characteristic is a feature that has different forms in a population Characteristic is a feature that has different forms in a population. (Hair color or eye color) Traits are the different forms of the characteristic. (Blonde or brown/ Brown or blue)

First Generation Plants Mendel used plants that were true-breeding for different traits of a characteristic. Ex. He crossed plants that had white flowers with plants that had purple flowers. All the 1st generation plants has purple flowers. What happened to the white flowers? P= purple (PP) p= white (pp)

Dominant trait- trait that showed up in the 1st generations, always a capital letter Recessive trait- trait that remained hidden when dominant trait was present, always a lowercase letter

Second Experiments When the 1st generation plants were allowed to self-pollinate the trait for white flowers appeared in the 2nd generation. P=purple (PP, Pp) p= white (pp)

Ratio A relationship between two different numbers that is often expressed as a characteristic Dominant to recessive ratio 3:1 (75:25) For every characteristic out of 100 trials– 75 will express the dominant trait and 25 will express the recessive trait.

Genes- one set of instructions for an inherited trait Allele- one of the alternative forms of a gene that governs a characteristic, such as hair color Phenotype- an organisms appearance or other detectable characteristic(EX./ Blonde hair, brown hair) Genotype- both inherited alleles together form the organisms genotype (BB, Bb, bb)

Genotypes Homozygous (purebred)- two dominant or two recessive alleles EX. PP or pp Heterozygous(hybrid) - one dominant and one recessive alleles EX. Pp

Punnett Squares Used to organize all the possible combinations of offspring from particular parents. Probability- the likelihood that a possible future event will occur in any given instance of the event. (Fraction, percentage, ratio)

Incomplete Dominance Also, known as codominance is when one trait is not completely dominant over the other. Each allele has its own degree of influence. Red Snapdragon- R1 White Snapdragon- R2

One gene, many traits One gene influences more than one trait. In white fur tigers with blue eyes, the gene that controls fur color also influences eye color.

Many genes, one trait Skin, hair, eye color are the result of several genes acting together. **Different combinations of alleles result in different shades of eye color.

Meiosis A process in cell division during which the number of chromosomes decreases to half the original number by two divisions of the nucleus, which results in the production of sex cells.

Homologous chromosomes- chromosomes that have the same sequence of genes and the same structure Sex chromosomes- one of the pair of chromosomes that determine the sex of an individual Pedigree- a diagram that shows the occurrence of a genetic trait in several generations of a family

Selective Breeding- organisms with desirable characteristics are mated.