Genetics Textbook Chapters Review Book Topic 3

Mendelian Genetics  1866 – Gregor Mendel (Austrian monk)  Studied inheritance of traits in pea plants Easy to grow, breed, controlEasy to grow, breed, control “True breeding” – meaning they always produce offspring with only one form of a trait“True breeding” – meaning they always produce offspring with only one form of a trait  Inheritance (heredity) – passing of traits onto the next generation the next generation  Known as the “father of genetics”

 Noticed that certain characteristics are passed onto offspring from generation to generation (traits)  Mendel controlled cross- pollination (breeding) between plants by removing the male organs from the flower  He then chose which plants reproduced plants reproduced

 Mendel called the parent plants the “P” generation  When crossing two “P” generation, the offspring produced were called the “F 1 ” generation (hybrids)  By crossing two “F 1 ” generation, Mendel could study if characteristics could skip generations  Creates the “F 2 ” generation

 Mendel studied seven different traits  Seed color  Flower color  Seed pod color  Seed shape or texture texture  Seed pod shape  Stem length  Flower position

 After his experiments Mendel concluded:  There must be two forms of a trait  Each form is controlled by an allele Allele – alternative form of a single gene passed from generation to generationAllele – alternative form of a single gene passed from generation to generation

Dominant allele (A) – form of the trait that appears in the F 1 generation (shown)Dominant allele (A) – form of the trait that appears in the F 1 generation (shown) oDoesn’t mean its stronger or more present in the population Recessive allele (a) – form of the trait that is masked in the F 1 generation (not shown)Recessive allele (a) – form of the trait that is masked in the F 1 generation (not shown)  Traits are different forms of a single gene Genes contain a segment of DNA which codes for a specific proteinGenes contain a segment of DNA which codes for a specific protein

 Law of Segregation  Homologous traits occur in pairs on homologous chromosomes homologous chromosomes  Separated from each other during gamete formation formation  Recombine at fertilization  One form of a trait is inherited from each parent parent

 Law of Dominance  Homozygous – an organism with two of the same alleles for a given trait (AA, aa) same alleles for a given trait (AA, aa)  Heterozygous – an organisms with two different alleles for a given trait (Aa) different alleles for a given trait (Aa) When heterozygous, the dominant trait will be observedWhen heterozygous, the dominant trait will be observed

 Three forms of dominance Homozygous dominant – AAHomozygous dominant – AA Heterozygous – AaHeterozygous – Aa Homozygous recessive - aaHomozygous recessive - aa

 Characteristics  The outward appearance does not always indicate which pair of alleles is present indicate which pair of alleles is present  Genotype – organism’s allele pairs (AA, Aa, aa) aa)  Phenotype – observable characteristic of an allele pair (tall, short, green, yellow) allele pair (tall, short, green, yellow)

 Possible for two organisms to have the same phenotype but different genotypes same phenotype but different genotypes  The genotype and phenotype of an organism is called a genome organism is called a genome

HOMEWORK #1  Define the following terms in your OWN words:  Genetics  Allele  Dominant  Recessive  Homozygous  Heterozygous  Genotype  Phenotype  Law of segregation  Hybrid  Law of independent assortment