GENETICS I.Heredity: How traits are passed from parents to offspring

II. GREGOR MENDEL ( ) -“Father of Genetics” -Austrian Monk from Job was to take care of the garden- worked with peas -Noticed that traits were passed from parent peas to their offspring -Before him people believed in the blending hypothesis

A. Why are pea plants good to study? - Reproduce quickly, easy traits to view, many offspring - Pea plants have DNA just like we do

A.Self Fertilization: Sperm and egg from the same plant produce offspring Offspring= Purebred

a. Offspring = Hybrid  heterozygous B. Cross Pollination process by which sperm from one flower's pollen fertilizes different flower’s eggs

HYBRID COCKAPOO COCKER SPANIEL + POODLE

HYBRID PUG + BEAGLE PUGGLE

HYBRID DOG AND WOLF DOG AND WOLF

male lion and a female tiger Liger

Peas!

GENETIC TERMINOLOGY DominantDominant RecessiveRecessive HomozygousHomozygous HeterozygousHeterozygous GenotypeGenotype PhenotypePhenotype TraitTrait AlleleAllele

Dominant allele- trait is always expressed - Written as capital letter - Ex. Tall= T Recessive allele- only expressed if no dominant allele is present (Dominant allele masks this one) - For a particular trait written as the same letter but lower case - Ex. Short= t Dominant & Recessive Alleles

Homozygous – identical alleles for a trait –TT, tt Heterozygous – not identical alleles for a trait –Tt

Genotype- the genes you get from parents –Two letters represent the two chromosomes –One from each parents – Ex: TT, Tt, tt Phenotype- the physical trait, what you look like –“Tall”, “short”, “yellow”, or “green”

Trait = A genetic characteristic Ex: Height TALL  alleles  SHORT

Flower Color Trait Allele- alternative forms of a gene

Reginald Punnett Introduction to Monohybrid Crosses Punnett Square- chart to predict offspring Monohybrid- looks at ONE trait Ex: Looking at just plant color, or just height, or just seed color

In Starfish being red is dominant over being pink. What would Patrick ’ s phenotype be? What would his genotype be? What would Patrick ’ s phenotype be? What would his genotype be?

PINK Because Patrick is pink… his phenotype is PINK rr And since pink is recessive – his genotype would be “ rr ”

Red pink Red is dominant over pink red Suppose we had a HETEROZYGOUS red starfish what would the genotype be?

Rr

Let’s do some… MONOHYBRID CROSSES! Monohybrid means we are only using ONE TRAIT

STEP by STEP 1.Select a “good” letter to use 2.Write down your “givens” 3.Determine parents and record 4.Set up Punnett Square 5.Determine genotypes & phenotypes of offspring (use percentages or fractions) (use percentages or fractions)

In pea plants, Tall is dominant to short Cross a Heterozygous Tall plant with a Homozygous Tall plant

Tt x TT Geno = 50% T T 50% T t Pheno = 100% Tall A A A TtTt T T t

In sponges, being blue is dominant over being yellow. Cross a heterozygous blue sponge with a yellow one.

Heterozygous Blue = Bb Recessive Yellow = bb so we cross… Bb x bb

Time for some Monohybrid Crosses on your own! Time for some LOONEY Monohybrid Crosses on your own!

MENDELS LAWS 1. Dominance & Recessiveness 2.Segregation 3. Independent Assortment

1. Dominance & Recessiveness one gene (dominant) can mask the other (recessive)

2. Segregation genes are separated during the formation of sex cells. Offspring inherit only one gene from each parent.

3. Independent Assortment genes for different traits inherited independently from each other In dihybrid crosses, gives you several possibilities –Ex: In Nemo- short fin can be inherited with a red body or an orange body- separate chromosomes

Independent Assortment

T TTEST EST CCRROOSSSSTTEST EST CCRROOSSSSCROSS

Test Cross: In a test cross, always cross the unknown genotype (TT or Tt) with homozygous recessive (tt). Using the context of what the results were, will determine which genotype is the unknown.

PEDIGREE male female