Gregor Gregor MendelMendel

(1822-1884)(1822-1884)

Responsible Responsible for the Laws for the Laws governing governing

Inheritance Inheritance of Traitsof Traits

Genetics – the study of Genetics – the study of heredity. heredity.

Mendel’s Experimental Mendel’s Experimental MethodsMethods

•Mendel Mendel hand-pollinatedhand-pollinated flowers using a flowers using a paintbrushpaintbrush

–He could He could snip (cut) the snip (cut) the stamensstamens to prevent self- to prevent self-pollinationpollination

•He traced traits through the He traced traits through the several generationsseveral generations

Seed Shape

Flower Position

Seed CoatColor

Seed Color

Pod Color

Plant Height

PodShape

Round

Wrinkled

Round

Yellow

Green

Gray

White

Smooth

Constricted

Green

Yellow

Axial

Terminal

Tall

Short

Yellow Gray Smooth Green Axial Tall

Section 11-1

Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants

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Different Traits of the Pea Plant

Mendel stated that Mendel stated that physical traits are physical traits are inherited as inherited as “particles”“particles”Mendel did not know Mendel did not know that the “particles” were that the “particles” were actually actually Chromosomes Chromosomes & DNA& DNA

Particulate InheritanceParticulate Inheritance

Alleles – different form of a gene

Genes – The chemical factors that determine traits

The Principle of Dominance

• States that some alleles are dominant and other are recessive.

• Dominant-genes that are expressed

• Recessive-genes that are not expressed if a dominant gene is present

P Generation F1 Generation F2 Generation

Tall Short Tall TallTall Tall Tall Short

Section 11-1

Principles of Dominance

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The Trait for Tallness

Applying the Law of Applying the Law of SegregationSegregation

Probability – the likelihood that a particular event will occur

Section 11-2

Tt X Tt Cross

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Punnett Squares The gene combinations that might Result from a genetic cross.

Section 11-1

Interest Grabber continued

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Parents

Long stems short stems

Red flowers white flowers

Green pods yellow pods

Round seeds wrinkled seeds

Yellow seeds green seeds

First Generation

All long

All red

All green

All round

All yellow

Second Generation

787 long: 277 short

705 red: 224 white

428 green: 152 yellow

5474 round: 1850 wrinkled

6022 yellow: 2001 green

Mendel’s Outcomes

Punnett Squares – Cont.

• Homozygous – Identical Alleles ex. TT , tt (“Purebred”)

• Heterozygous – 2 different Alleles ex.Tt

(“Hybrid”)• Phenotype – Physical

Characteristics• Genotype – Genetic

Make-up or combination of alleles TT, Tt, tt