Transcript Genetics
All of these animals don’t look alike, but you recognize them as dogs. What do they have in common? Genetics Genetics is... • The study of the passing on of traits from parent to offspring • http://www.youtube.com/watch?v=bVk0twJYL6Y& list=PL05EB0E51EF56E24B&index=10 Chromosomes • In the nucleus • In pairs • Carry genes • Controls all traits of an organism • controls the production of proteins • Chromosomes are made of DNA • DNA is made of genes • DNA / genes codes for proteins • Proteins give you your traits! • genes - are the units of heredity • Represented with letters • You have 2 genes for each trait (1 from mom & 1 from dad) • Also Called ALLELES Mendel’s Experiments http://www.youtube.com/watch?v=GTiOETaZg4w Experiment 1 • Short + Short = Short • Called this “True breeding” • Also called “purebred” Experiment 2 Tall + Tall = Short & Tall Called “not true breeding Also called hybrid Experiment 3 Purebred TALL + purebred short = all hybrid TALL Discovered some genes dominant, others recessive Experiment 4 Crossed two hybrid TALL and got 3 TALL & 1 short When 2 hybrids are crossed, the result is a Dominant to recessive ratio of 3:1 Dominant • Expressed trait • capital letter vs. Recessive • Hidden trait • lower case letter Cheat Sheet • Dominant + Dominant = Dominant • Dominant + Recessive = Dominant • Recessive + Recessive = Recessive Dominant vs. Recessive Class activity Example New Vocab • What you look like on the inside • Your letters • Examples: BB, Bb, or bb Genotype Phenotype •What you look like on the outside •Ex. Tall or short Homozygous Heterozygous Homozygous • The same • 2 upper case OR 2 lower case • Ex. TT or tt • Purebred • Dominant or recessive Heterozygous • Different Letters • 1 upper case & 1 lower case • Ex. Tt or Bb • Hybrid • Shows the dominant trait Genetics with a smile activity Dragon Genetics Activity Probability • Chances of something happening • written as a percentage or fraction or a ratio • ex. The chances of you being a girl or boy is 50% or 1/2 Punnett Squares •A chart used to show the possible gene combinations in a cross Steps for making a Punnett Square • 1- choose a letter to represent the gene in the cross (the first letter of the dominant trait) • 2 - Write the genotypes of the parents outside, on top & on the side of the Punnett square (1 letter for each box) • 3- Fill in the squares by writing the gene combinations in the boxes •4- Determine the phenotypes of the offspring and calculate probability •Each box of 4 represents 25% chance 1 allele from Parent 1 1 allele from Parent 1 1 allele from Parent 2 Genotype Genotype Of Of Offspring Offspring 2 letters 2 letters (25% chance) (25% chance) 1 allele from Parent 2 Genotype Genotype Of Of Offspring Offspring 2 letters 2 letters (25% chance) (25% chance)