FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Chapter 11 Introduction To Genetics Section 11-3 Exploring...

FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT

Chapter 11Introduction To Genetics

Section 11-3Section 11-3Exploring Mendelian Exploring Mendelian

GeneticsGenetics


Gregor Mendel

Wanted To Know If:Wanted To Know If:

Segregation Was Truly IndependentSegregation Was Truly Independent oror

Does The Segregation Of One Pair Does The Segregation Of One Pair Of Alleles Affect The Segregation Of Alleles Affect The Segregation

Of Another Pair Of Alleles????Of Another Pair Of Alleles????


Independent Assortment

Mendel Performed AMendel Performed ATwo Factor CrossTwo Factor Cross

–He Crossed He Crossed

Round/Yellow Round/Yellow RRYYRRYY–WithWith

Wrinkled/Green Wrinkled/Green rryyrryy

This Provided The FThis Provided The F11 Hybrids That Hybrids That He Needed.He Needed.



F1 Hybrid F1 Hybrid RrYyRrYy



9 : 3 : 3 : 199 : 39 : 3 : 3


Two Factor Cross F2

All FAll F11 Plants Were Plants Were

Heterozygous or HybridHeterozygous or Hybrid

In The FIn The F22 Cross Would Cross Would

1.1. The Dominant Alleles Stay TogetherThe Dominant Alleles Stay Together

2.2. Or Would They Segregate Independently Or Would They Segregate Independently So Any Combination Of Alleles Would Be So Any Combination Of Alleles Would Be Possible??????Possible??????


Two Factor Cross F2 Results

556556 Seeds ProducedSeeds Produced

315 Round/Yellow315 Round/Yellow FF11 Parental ParentalPhenotypesPhenotypes32 Wrinkled/Green32 Wrinkled/Green

PlusPlus

209 Unique Phenotypes209 Unique Phenotypes Can Only FormCan Only Form

ViaVia

9:3:3:19:3:3:1 IndependentIndependent

AssortmentAssortment


Two Factor Cross F2 Results

The Alleles For Seed Shape And The Alleles For Seed Shape And Color Segregated IndependentlyColor Segregated Independently

INDEPENDENT ASSORTMENTINDEPENDENT ASSORTMENT did occur did occur..

Therefore These AllelesTherefore These Alleles DO NOTDO NOT

Influence Each Others Influence Each Others InheritanceInheritance


Key Concept

The Principle Of Independent The Principle Of Independent Assortment States ThatAssortment States That

Genes For Different TraitsGenes For Different TraitsCan Segregate Independently Can Segregate Independently

During The Formation Of Gametes.During The Formation Of Gametes.


Summary of Mendel’s Principles

1.1. Inheritance of Biological Inheritance of Biological Characteristics Is Determined By Characteristics Is Determined By Individual Units Known As Genes.Individual Units Known As Genes.

In Organisms That Reproduce In Organisms That Reproduce Sexually, Genes Are Passed From Sexually, Genes Are Passed From Parents To Their Offspring.Parents To Their Offspring.



2.2. Where Two or More Forms Of The Where Two or More Forms Of The Alleles Exist, Alleles Exist,

Some Forms Of The Allele Many Some Forms Of The Allele Many BeBe

DominantDominantAnd Others May BeAnd Others May Be

Recessive.Recessive.



3.3. In Most Sexually Reproducing In Most Sexually Reproducing Organisms, Each Adult Has Two Organisms, Each Adult Has Two Alleles In Each Gene – One From Alleles In Each Gene – One From Each ParentEach Parent

4.4. These Alleles Are Segregated These Alleles Are Segregated From Each Other When Gametes From Each Other When Gametes Are Formed.Are Formed.



5.5. Alleles Contained In Different Alleles Contained In Different Genes Usually Segregate Genes Usually Segregate Independently Of One AnotherIndependently Of One Another


Beyond Dominant & Recessive Alleles

Key ConceptKey Concept::

Some Alleles Are Neither Some Alleles Are Neither Dominant Nor Recessive, And Dominant Nor Recessive, And Many Traits Are Controlled By Many Traits Are Controlled By Multiple Alleles or GenesMultiple Alleles or Genes..


Incomplete Dominance

Red Flower Crossed With White Flower Red Flower Crossed With White Flower Results In Pink Flower.Results In Pink Flower.

In Incomplete Dominance The In Incomplete Dominance The Heterozygous Phenotype Is Heterozygous Phenotype Is Between The Homozygous Between The Homozygous

Phenotypes.Phenotypes.((Both Alleles Expressed In One Cell)Both Alleles Expressed In One Cell)


Codominance

• Both Alleles Completely ExpressedBoth Alleles Completely Expressed

Red Hair Cattle Crossed With White Red Hair Cattle Crossed With White Haired Cattle Produce Roan (Pink Haired Cattle Produce Roan (Pink

Brown) Cattle That Have Both Brown) Cattle That Have Both Colored Hairs.Colored Hairs.

(Both Alleles Expressed Independently)(Both Alleles Expressed Independently)


Codominance

RED WHITE

ROAN


Multiple Alleles

• A Gene Is Controlled By >2 Alleles.A Gene Is Controlled By >2 Alleles.– Individuals Can Only Have 2 AllelesIndividuals Can Only Have 2 Alleles– Populations Can Have More Than TwoPopulations Can Have More Than Two

• Rabbit Fur ColorRabbit Fur Color

• Blood TypesBlood Types

• Eye ColorEye Color


Multiple Alleles


Polygenic Traits

• Phenotypes Produced By The Phenotypes Produced By The Interaction Of Several Genes.Interaction Of Several Genes.–Human Skin Color Is Controlled By Human Skin Color Is Controlled By

More Than 4 Different Genes.More Than 4 Different Genes.

–Eye Color is Controlled By At Least 3 Eye Color is Controlled By At Least 3 GenesGenes


Applying Mendel’s Principles

Thomas Hunt Morgan – early 1900’sThomas Hunt Morgan – early 1900’s–Drosophila melanogasterDrosophila melanogaster• Easy To RaiseEasy To Raise• Produces Numerous Offspring Every 14 Produces Numerous Offspring Every 14

DaysDays• Large ChromosomesLarge Chromosomes• Susceptible To MutagensSusceptible To Mutagens

FOOTHILL HIGH SCHOOL SCIENCE DEPARTMENT Chapter 11 Introduction To Genetics Section 11-3 Exploring...

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