GENETICSGENETICS

GREGOR MENDELGREGOR MENDEL (1822- (1822- 1884)1884)

Self FertilizationOffspring= Purebred

Cross Fertilization Offspring = Hybrid

CROSS POLLINATIONCROSS POLLINATION

HYBRID HYBRID

COCKAPOCOCKAPOOO

COCKER SPANIEL

+POODLE

HYBRIDHYBRIDPUG

+BEAGLE

PUGGLE

HYBRIDHYBRID

DOG DOG ANDAND WOLFWOLF

male lion and

a female tiger

Liger

Peas!

GENETIC GENETIC TERMINOLOGYTERMINOLOGY

•DominantDominant•RecessiveRecessive•HomozygousHomozygous•HeterozygouHeterozygouss

•GenotypeGenotype•PhenotypPhenotypee

•TraitTrait•AlleleAllele

• Dominant allele- trait is always expressed if present

- 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 sameletter but lower case

- Ex. Short= t

Dominant and Recessive Alleles

• Genotype- the genes you get from your parents– Two letters represent the two alleles– One from mom one from dad – TT, Tt, tt

• Phenotype- the physical trait, what you look like – Tall short, yellow or green – TT, tt what is the phenotype??

• Homozygous - the same alleles for a gene – TT, tt

• Heterozygous - having different alleles for a gene– Tt

Trait = HeightTrait = Height

TALL SHORT alleles

Flower Color Trait

Gene- unit of inherited information in DNA Allele- alternative form of a gene ( white purple)

Test Cross- mate an unknown genotype ( TT or Tt) with homozygous recessive (tt)

Reginald PunnettReginald Punnett

In Starfish In Starfish being being redred is is

dominant over dominant over being being pinkpink.. What would What would

PatrickPatrick’’s s phenotypephenotype be? What be? What would his would his

genotypegenotype be? be?

Because Patrick is pink… his

phenotype is PINKPINK

And since pink is

recessive – his

genotype

would be “rrrr ”

RedRed is dominant over

pinkpinkSuppose we

had a HETEROZYGO

US redred starfish what

would the genotype be?

Rr

LetLet’’s do some… s do some… MONOHYBRID MONOHYBRID

CROSSES!CROSSES!

MonohybridMonohybrid means means we are only using we are only using

ONE TRAITONE TRAIT

STEP by STEPSTEP by STEP1.1. Select a Select a ““goodgood”” letter to use letter to use

2.2. Write down your Write down your ““givensgivens””

3.3. Determine parents and recordDetermine parents and record

4.4. Set up Punnett SquareSet up Punnett Square

5.5. Determine genotypes & Determine genotypes & phenotypes of offspring phenotypes of offspring

(use percentages or fractions)(use percentages or fractions)

In pea plants being In pea plants being Tall is dominant over Tall is dominant over

being shortbeing short

Cross a Heterozygous Cross a Heterozygous Tall plant with a Tall plant with a

Homozygous Tall plantHomozygous Tall plant

Aa x AA

Geno = 50% AA50% Aa

Pheno =100% Tall

A

A

A

In sponges, In sponges, beingbeing blueblue

is dominant is dominant over beingover being

yellow.yellow.Cross a Cross a

heterozygouheterozygous blue s blue

sponge with sponge with a yellow a yellow

one.one.

HeterozygoHeterozygous us BlueBlue = = BbBbRecessive Recessive YellowYellow = bb = bb so we so we cross…cross…

Bb x Bb x bbbb

Time for someTime for some

LOONEY Monohybrid Monohybrid Crosses onCrosses on your own! your own!

Red Red is is

dominant dominant over over BlueBlue

TTEESSTT CCRROOSSSS

MENDELS LAWSMENDELS LAWS

1. Dominance & Recessiveness

2.Segregation3. Independent

Assortment

PEDIGREEPEDIGREEmale female