Parental (P) generation - The original cross.
F1 generation - Offspring of the P generation.
F2 generation - Offspring of the F1 generation.
Allele - A gene choice - 2 choices for 1 gene.
Homozygous - Has the same allele (choice) on both homologous chromosomes.
True breeding - Has the same allele (choice) on both homologous chromosomes.
Heterozygous - Has the different alleles (choices) on the homologous chromosomes.
Principle of dominance - One allele can mask the expression of another in a hybrid.
Dominant - Always expressed in a heterozygote.
Recessive - Always hidden in a heterozygote.
Genotype - The alleles the individual carries for a given trait - the letters.
Phenotype - The expression of that trait - what you look like.
Punnett square - Predicts the ratio of the genotype and phenotype of potential offspring.
Gametes - Sperm or eggs
Monohybrid cross - Both parents are heterozygous for 1 trait.
Test cross - Do you have a heterozygote or a homozygous dominant? Cross the unknown with a homozygous recessive.
Dihybrid cross - Both parents are heterozygous for 2 traits.
Multiple alleles - (of same gene) - are traits which have more than 2 alleles in the population.
Codominant - Both traits are expressed.
Erythroblastosis fetalis - Rh- woman has a Rh+ baby, her antibodies can kill her second Rh+ baby.
Polygenic inheritance - Is where multiple genes all contribute to the phenotype in additive fashion.
Phenylketonuria PKU - A homozygous recessive disorder - These people lack the enzyme to convert phenylalanine (amino acid) into the amino acid tyrosine.
Phenylalanine (Amino acid) ------> Tyrosine (Amino acid) (They instead make a neural toxin)
Sickle cell anemia - A homozygous recessive disorder - Red blood cells are sickle shaped and don't flow through vessels easily.
Heterozygote advantage - The heterozygote does better than both the homozygotes. - SS Ss ss
Cystic fibrosis - A homozygous recessive disorder - The secretions of the body are thick and abnormal.
Huntington's disease - A dominant allele disorder - It leads to muscle spasms, personality changes, and insanity.
Genotype Phenotype Homozygous Dominant Bent / Bent (BB) - Bent little fingers ( True Breeder ) Heterozygous Bent / Straight (Bb) - Bent little fingers Homozygous Recessive Straight / Straight (bb) - Straight little fingers ( True Breeder )
Possible Genotype Phenotype AA, AO Type A blood BB, BO Type B blood AB (Codominant) Type AB blood OO Type O blood LIGHT MEDIUM DARK aabbccdd ---------> AaBbCcDd ------------> AABBCCDD