GENETICS UNIT SB2 C. USING MENDELS LAWS, EXPLAIN THE ROLE OF MEIOSIS IN REPRODUCTIVE VARIABILITY Genetics = the field of biology devoted to understanding how characteristics are transmitted from parents to offspring Heredity = the transmission of characteristics from parents to offspring MENDEL - father of modern genetics = laid the groundwork - experimented with garden peas - looked for traits = specific characteristics MENDEL (CONT) Cross pollination: sexual reproduction between two different flowering plants. Self pollination: sexual reproduction done within the same flowering plant. P 1 generation = parental generation F 1 generation = offspring of the parental generation F 2 generation = offspring of the F 1 generation MENDELS LAWS Mendels 1st Law = Law of Segregation 1) Organisms inherit two copies of each gene, one from each parent 2) Organisms donate one copy of each gene in their gametes. MENDELS LAWS Mendels 2nd Law = Law of Independent Assortment 1) The presence of one trait does not affect the appearance of another trait BASICS OF GENETICS - Gene = a segment of DNA on a chromosome that controls a specific trait - because chromosomes come in pairs, genes come in pairs BASICS OF GENETICS -Allelle= alternative form of a gene -alleles: letters -There are 2 alleles or letters per gene -Capital letters=dominant alleles -Lowercase letters= recessive alleles -Each allele has a specific location which is called a locus or loci BASICS OF GENETICS (CONT) - Allele = each of several forms of a gene - aka: letters - each allele has a specific location on a chromosome (= locus) - capital letters = dominant alleles - lowercase letters = recessive alleles TYPES OF ALLELES - Homozygous = both alleles are alike - homozygous dominant = both capital letters = BB - homozygous recessive = both lowercase letters = bb - Heterozygous = alleles are different = Bb TYPES OF ALLELES Genotype: genetic make up of the organism Aka: the letters (BB,Bb,bb) Phenotype: the appearance of the organism or physical features as a result of its genotype. Aka: what do you see? ( brown, blue, black)