Chapter 11 Introduction To Genetics

1
Chapter 11Introduction To Genetics

• Section 11-3
• Exploring Mendelian Genetics

2
Gregor Mendel

• Wanted To Know If
• Segregation Was Truly Independent or Does The
  Segregation Of One Pair Of Alleles Affect The
  Segregation Of Another Pair Of Alleles????

3
Independent Assortment

• Mendel Performed ATwo Factor Cross
• He Crossed
• Round/Yellow RRYY
• With Wrinkled/Green rryy
• This Provided The F1 Hybrids That He Needed.

4
Independent Assortment

• F1 Hybrid RrYy

5
(No Transcript)
6
Independent Assortment
9 3 3 1
9
9 3
9 3 3
7
Two Factor Cross F2

• All F1 Plants Were
• Heterozygous or Hybrid
• In The F2 Cross Would
• The Dominant Alleles Stay Together
• Or Would They Segregate Independently So Any
  Combination Of Alleles Would Be Possible??????

8
Two Factor Cross F2 Results
556 Seeds Produced
315 Round/Yellow F1 ParentalPhenotypes
32 Wrinkled/Green F1 ParentalPhenotypes
Plus
209 Unique Phenotypes Can Only Form
Via
9331 Independent
9331 Assortment
9
Two Factor Cross F2 Results

• The Alleles For Seed Shape And Color Segregated
  Independently
• INDEPENDENT ASSORTMENT did occur.
• Therefore These Alleles DO NOT Influence Each
  Others Inheritance

10
Key Concept

• The Principle Of Independent Assortment States
  ThatGenes For Different TraitsCan Segregate
  Independently During The Formation Of Gametes.

11
Summary of Mendels Principles

1. Inheritance of Biological Characteristics Is
   Determined By Individual Units Known As
   Genes.In Organisms That Reproduce Sexually,
   Genes Are Passed From Parents To Their Offspring.

12
Summary of Mendels Principles

• Where Two or More Forms Of The Alleles Exist,
• Some Forms Of The Allele Many Be DominantAnd
  Others May BeRecessive.

13
Summary of Mendels Principles

1. In Most Sexually Reproducing Organisms, Each
   Adult Has Two Alleles In Each Gene One From
   Each Parent
2. These Alleles Are Segregated From Each Other When
   Gametes Are Formed.

14
Summary of Mendels Principles

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

15
Beyond Dominant Recessive Alleles

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

16
Incomplete Dominance

• Red Flower Crossed With White Flower Results In
  Pink Flower.
• In Incomplete Dominance The Heterozygous
  Phenotype Is Between The Homozygous
  Phenotypes.(Both Alleles Expressed In One Cell)

17
(No Transcript)
18
Codominance

• Both Alleles Completely Expressed
• Red Hair Cattle Crossed With White Haired Cattle
  Produce Roan (Pink Brown) Cattle That Have Both
  Colored Hairs.
• (Both Alleles Expressed Independently)

19
Codominance
RED
WHITE
ROAN
20
Multiple Alleles

• A Gene Is Controlled By gt2 Alleles.
• Individuals Can Only Have 2 Alleles
• Populations Can Have More Than Two
• Rabbit Fur Color
• Blood Types
• Eye Color

21
Multiple Alleles
22
Multiple Alleles
23
Multiple Alleles
24
Polygenic Traits

• Phenotypes Produced By The Interaction Of Several
  Genes.
• Human Skin Color Is Controlled By More Than 4
  Different Genes.
• Eye Color is Controlled By At Least 3 Genes

25
Applying Mendels Principles

• Thomas Hunt Morgan early 1900s
• Drosophila melanogaster
• Easy To Raise
• Produces Numerous Offspring Every 14 Days
• Large Chromosomes
• Susceptible To Mutagens