Genetics ature=endscreen&NR=1&v=YxKF dQo10rE

Gregor Johann Mendel Austrian monk How do mothers and fathers pass down traits to their children? Mendel tested his idea of heredity on pea plants =EvR_Sdm1orUhttp:// =EvR_Sdm1orU

Pea plants is normally self- pollinating Easy to control the parental crosses Easily grown and matured quickly, producing many seeds Allowed him to study many generations over a relatively short period of time Showed several pairs of obvious, contrasting traits

Observed traits were called phenotypes

After several years of self-pollinating the pea plants, Mendel established purebred plants When self-pollinated, these plants always create plants that look like themselves

Mendel also cross bred the purebred plants that were different for only one contrasting pair of traits –The purebred parent plants were called the P generation –The offspring were called hybrids –First generation of hybrids – F1 generation –Second generation of hybrids – F2 generation

Results? The F1 generation hybrids had the same trait The traits of tallness dominated the traits of dwarf-ness Mendel called them the dominant traits Trait that was not expressed = recessive trait

Mendel crossed his F1 generation plants to determine whether they were identical to the P generation plants If they were, then F1 cross would produce only tall plants F2 generation yielded 3 tall plants and 1 dwarf plant

Phenotypic ratio of F2 was 3:1 –Proportion of individuals in a generation that express a certain trait The F1 hybrid were different from the purebred tall plants

The gene for plant height has two different forms (alleles): tall and dwarf –Tall = dominant –Dwarf = recessive He suggested that each plant’s phenotype was determined by a PAIR of alleles that could be identical or different The only way a plant to develop as a dwarf is if both its alleles are recessive

Mendel’s Law of Segregation Members of a pair of alleles for a given trait are segregated (separated) when gametes are formed

Once Mendel came up with the Law of Segregation, he was able to describe the gene makeup, or genotype He used letters of the alphabet to represent the genes The allele for dominant trait was represented by T The allele for recessive trait was represented by t

Purebred tall plant = TT Purebred dwarf plant = tt Hybrid tall plant = Tt Homozygous Heterozygous

Monohybrid Cross Drag-and-Drop Genetics: Monohybrid Drag-and-Drop Genetics: Monohybrid

MONOHYBRID PROBLEMS Problems dealing with one trait only ie. height or colour 1.Write the cross 2.Produce the gametes 3.Draw the Punnett square 4.List the phenotype and genotype ratios

1. In dinosaurs, the gene for sharp teeth (S) is dominant over the gene for dull teeth (s). Cross a heterozygous sharp toothed dinosaur with a dull- toothed dinosaur to produce the F1 (first generation) offspring. 2. Cross a homozygous sharp toothed dinosaur with a homozygous dull-toothed dinosaur to produce the F1 offspring. 3. Now cross two of the F1 generation offspring from question #2 to produce the F2 offspring.