What is Genetics?

A Brief Review..Greetings

Understanding Genetics

The study of how traits are passed on from one organism to it’s offspring.Each cell has chromosomes in the nucleus.Chromosomes contain DNA, which determine the genetic make-up of an organism.

Chromosomes

The Father of Genetics

• Gregor Mendel• Monk-liked pea plants• Bored with religion• Cross pollinated pea

plants• Tall = dominant (T)• Short = recessive (t)• Dominant more powerful

than recessive

Peas

Trait ExpressionTrait Expression• DominantDominant

• Stronger traitStronger trait• Seen most oftenSeen most often• Demonstrated Demonstrated

with a CAPITAL with a CAPITAL letterletter

• Expressed if Expressed if present with a present with a recessive generecessive gene

• RecessiveRecessive• Weaker traitWeaker trait• Seen less oftenSeen less often• Demonstrated Demonstrated

with a lower case with a lower case letterletter

• Not expressed if Not expressed if present with a present with a dominant gene, dominant gene, but not lost….but not lost….

Homo/Heterozygous Homo/Heterozygous TraitsTraits

Homozygous• Purebred• Can be

dominant or recessive

• Both genes are the same

• TT or tt

Heterozygous• Hybrid (mutt)• One dominant

gene, one recessive gene

• Both genes are different

• Tt

Heterozygous and Homozygous

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Genotype and Phenotype

Genotype The genetic makeup of

an organism For example

TTTttt

Phenotype The outward expression of a

gene For example

Tall or short Brown or blue eyes Straight or curly hair

Genotype and Phenotype

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Incomplete DominanceIncomplete Dominanceo Neither is stronger Neither is stronger

than the otherthan the othero Offspring is Offspring is

blended, a blended, a combination combination between both traitsbetween both traits

o For instance, red For instance, red flower mated with flower mated with white flower = pinkwhite flower = pink

Punnett Square Movie

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Punnett SquaresPunnett Squares Tall = (TT) X Short (tt)

t

t

Tt Tt

Tt Tt

T T

Punnett Squares Tall = (Tt) X tall (Tt)

T

t

TT Tt

Tt tt

T t

Punnett Squares Tall = (Tt) X Short (tt)

t

t

Tt tt

Tt tt

T t

The EndThe End Words to rememberWords to remember

DominantDominant RecessiveRecessive HomozygousHomozygous PurebredPurebred HeterozygousHeterozygous hybridhybrid Punnett SquarePunnett Square Incomplete Incomplete

DominanceDominance