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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
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