GENETICS NOTES

Every living thing inherits traits from its parent(s)Genetics = study of heredity

Gregor Mendel = father of geneticsAustrian monk in the mid 1800sworked with pea plantstrue breeding: plants that self pollinate; offspring are identical to parentMendel looked at several traits of the pea plants (height, seed color, flower color)trait = characteristicMendel would cross pollinate plants

Ex: cross tall with shortoriginal pair of plants = P (parental) generationoffspring of P generation = F1 generationoffspring of F1 generation = F2

Genes = regions of DNA that determine traits

Alleles = different forms of a geneEx: gene for height

1 allele = tall 1 allele = short

A dominant allele hides a recessive alleledominant = capital letterrecessive = lowercase

Ex: Tall = dominant = TShort = recessive = t

TT = Tall RR = Roundtt = short rr = wrinkled HOW DID THE YELLOW POD REAPPEAR?Tt = Tall Rr = Round

Homozygous = 2 identical alleles for a trait Ex: TT or tt

Heterozygous = 2 different alleles for a trait Ex: Tt

Genotype = genetic makeup Ex: Tt, tt, or TT

Phenotype = physical trait Ex: tall or short

Probability = likelihood an event will occurEx: flip a coin 1:2 heads 1:2 tailsUsed to predict average outcome of large # of events

NOT exact.Probability is used to predict outcomes of genetic crosses

Punnett Square = diagram to determine possible outcomes of genetic crossesMonohybrid = cross one trait

1. Cross a homozygous tall plant (TT) with a short plant (tt).

2. Cross a heterozygous tall plant (Tt) with a short plant (tt).

3. Cross 2 heterozygous tall plants.

Mendel’s 3 Principles1. Principle of Dominance: some alleles are dominant and others are recessive - capital letter = dominant (T = tall)

- lowercase = recessive (t = short)2. Principle of Segregation: alleles separate when gametes form(a sperm or egg only gets one allele)gametes = sex cells (sperm or eggs)Humans have 46 chromosomes 23 come from mom (egg) & 23 come from dad (sperm) 1 trait has 2 alleles (one from mom and one from dad) Ex: Bb b comes from dad & B comes from mom

3. Principle of Independent Assortment: one trait does not influence the inheritance of another trait