Chp. 10 GENETICS

GENETICS The study of heredity Traits- characteristics that are inherited Heredity- passing on of characteristics from parent to offspring

ALLELE Gene form for each variation of a trait of an organism One allele is inherited from the female (mom) & the other from the male (dad)

DOMINANT GENE Visible, observable trait of an organism Masks the recessive form of the trait Represented by a capital letter (T, S)

RECESSIVE GENE Hidden trait of an organism Masked by the dominant gene Represented by a lower case letter (t, s)

PHENOTYPE The way an organism looks Physical appearance Ex: tall, short, blonde hair, brown eyes

GENOTYPE The gene combination of an organism Two letters representing the genes Ex: TT, Ss, ss

HOMOZYGOUS/PURE The 2 alleles for the trait are the same Ex: TT, SS, tt, ss Homozygous recessive- the two alleles are recessive. Ex: tt, ss Homozygous dominant- two alleles are dominant. Ex: TT, SS

HETEROZYGOUS/HYBRID The two alleles for the trait are different A capital letter and a lower case letter Ex: Tt, Ss Also known as HYBRID!

LAW OF SEGREGATION The two alleles for each trait separate during meiosis During fertilization, the two alleles for that trait unite

LAW OF INDEPENDENT ASSORTMENT A random distribution of alleles occurs during gamete formation Genes on separate chromosomes sort independently during meiosis Ex. Plant height & flower color

INHERITANCE OF TRAITS P Generation- parents F1- first filial generation, offspring of parents F2- second filial generation, offspring of F1

PUNNETT SQUARES Monohybrid cross- results is a 3:1 phenotypic ratio of dominant to recessive. Uses one trait (height) A true monohybrid cross involves two heterozygous individuals

DIHYBRID CROSSES Cross involving two different traits Ex: round yellow seeds vs. wrinkled green seeds The alleles combine in four different ways A true dihybrid cross involves two individuals that are heterozygous for both traits Results in a 9:3:3:1 phenotypic ratio