7Genetics

Gregor Mendel and the Garden Pea (page 117)

Genetics: the study of heredity; how an offspring gets traits from their parents.

Describe Gregor Mendel.Who? Monk (priest)What? Curious gardener trained in math and scienceWhen? 1860sWhere? Austria

How did Mendel add a “twist” to his research? He used math to draw conclusions from his observations.

List 4 reasons why the garden pea was a good subject for scientific study.

1. easy to grow2. grow quickly3. large number of offspring; a lot of quantitative

data4. plants have both male and female parts;

fertilization can be controlled

Define self-fertilization: plant that fertilizes itself

Define cross-fertilization: plant that is fertilized by another plant

Mendel’s Experiment (page 118)

Step One: Creating the parent (P) generation (Pure Breeding)• allowed plants to self-fertilize for many generations• collected and grew the seeds from the plants• observed that purple flowering seeds grew purple flowers and white flowering seeds grew white flowers.

CREATED PURE BREEDING PLANTS

Step Two: Cross breeding plants from parent generation to create F1 generation.• used pollen from purple flower and fertilized white flower• collected and grew seeds• only purple flowers grew from this generation.

Results of Step Two: When Mendel cross fertilized a true breeding purple plant with a true breeding white plant, all of the offspring had purple flowers.

Mendel asks…Where did the white flowers go?Hypothesis…even though the flowers were all purple, they must be carrying around some kind of white flowering plant “factors”.

Step Three: Self-pollinate one of the offspring from the F1 generation to create the F2 generation.• self-fertilized a purple flowered plant from the F1 generation• collected and grew the seeds• purple and white flowers showed up on the plants

For every 4 flowers on the plants, 1 one was white and 3 were purple.

3:1 Ratio in the F2 generation

Mendel’s Quantitative Results: Total Pea Plants in F2 Generation = ___________ Pea Plants with Purple Flowers = ___________Pea Plants with White Flowers = ___________

What % of Mendel’s F2 Generation had purple flowers?(purple flowers / total flowers) x 100 = __________%

What % of Mendel’s F2 Generation had white flowers?(white flowers / total flowers) x 100 = ___________%

The ratio of purple to white flowers in Mendel’s F2 Generation is ____ : _____.

List three other pea plant traits that Mendel studies.1. 2. 3.

Trait Contrasting Form of Traits

F2 Generation Ratios Which trait showed up more often?

Flower Color Purple and White 705:224 Purple

Seed Color 6,022:2,001 Yellow

Round and Wrinkled

Round

Pod Color 428:152

Mendel’s Experiments (page 119)Use Table 7-1 on page 119 to complete the missing boxes in the chart below.

Contrasting Traits in Pea Plants

Mendel’s Explanation of the Results (VERY IMPORTANT VOCABULARY)

Factors: “information” that is trasfered from parent to offspring

Traits: characteristic you get from your parents (ex: hair color)

Alleles: different forms of this information; types of traits (ex: brown vs. blonde)

Principle of Dominance: some alleles are more dominant than others

Dominant Traits: traits that show up more often in a population; stronger allele (ex: brown eyes)

Recessive Traits: traits that show up less often in a population; weaker allele (ex: red hair)

Genotype: type of alleles passed from parent to offspring

Homozygous (pure bred): contain two of the same allele for a trait (ex: both parents pass brown eyes to their offspring

Heterozygous (hybrid): contain two different alleles for a trait (ex: one parent passed brown eyes and the other passed blue eyes)

Dominant Allele + Dominant Allele = dominant traitDominant Allele + Recessive Allele = dominant traitRecessive Allele + Recessive Allele = recessive trait

Phenotype: physical appearance of a trait (brown eyes)

Section 7-1 Quiz

The Principle of Dominance Related to some SimpleThe Principle of Dominance Related to some Simple

Human TraitsHuman Traits

TRAIT Your Phenotype

Dominant trait?

Recessive trait?

Class RatioDominant to Recessive

Frequency % of your trait

Tongue rolling

Skin appearance of freckles

Hairline

Dimples

PTC

Ear lobe

Bent fingers

Thumb

Finger hair

Mendel’s Conclusions (page 122)

Law of Segregation: when gametes (sex cells) are made, the two alleles for each trait will separate; gametes only carry one of each allele.

Law of Independent Assortment: alleles for different traits segregate into gametes (sex cells) independently from one another

Bill Nye: Understanding Basic Genetics

Segregation of Alleles and Fertilization of Gametes

Directions: Complete each chart using the given information. Collect quantitative data using the information within the completed chart.

1.True breeding Yellow Seeds x True Breeding Green SeedsDominant Trait: ______________ Domiant Allele: _____Recessive Trait: ______________ Recessive Allele: _____

# Dominant _________

# Recessive _________

% Dominant _________

% Recessive ________

Ratio ____: ____

Segregation of Alleles and Fertilization of Gametes

Directions: Complete each chart using the given information. Collect quantitative data using the information within the completed chart.

2. Hybrid Green Pea Pod x Hybrid Green Pea PodDominant Trait: ______________ Domiant Allele: _____Recessive Trait: ______________ Recessive Allele: _____

# Dominant _________

# Recessive _________

% Dominant _________

% Recessive ________

Ratio ____: ____

Segregation of Alleles and Fertilization of Gametes

Directions: Complete each chart using the given information. Collect quantitative data using the information within the completed chart.

3. True Breeding Round Seed x Hybrid Round SeedDominant Trait: ______________ Domiant Allele: _____Recessive Trait: ______________ Recessive Allele: _____

# Dominant _________

# Recessive _________

% Dominant _________

% Recessive ________

Ratio ____: ____

Segregation of Alleles and Fertilization of Gametes

Directions: Complete each chart using the given information. Collect quantitative data using the information within the completed chart.

4. True Breeding Wrinkled Seeds x True Breeding Round SeedsDominant Trait: ______________ Dominant Allele: _____Recessive Trait: ______________ Recessive Allele: _____

# Dominant _________

# Recessive _________

% Dominant _________

% Recessive ________

Ratio ____: ____

Punnett Square: diagram used to show genetic crosses (segregation and fertilization of alleles)

Probability: the likelihood that something will happen

Visualizing Mendel’s Model (pages 120-1)

•Choose a letter to represent the trait being modeled

•Upper case letter represents dominant form of trait (dominant allele)

•Lower case letter represents recessive allele

•Parent genotypes go on the outside of the box (segregating one allele to each box)

•Offspring genotypes (fertilized together) go on the inside of the boxes

        

Phenotype of the Parent Generation: _______and_____________Genotype of the Parent Generation: _______and_____________

Punnett Square Modeling Mendel’s Parent to F1 Generation: Flower Color

Punnett Square Modeling Mendel’s F1 to F2 Generations: Flower Color

Phenotype of the Parent Generation: _______and_____________Genotype of the Parent Generation: _______and_____________

Sponge Bob GeneticsPunnett Square Quiz

Law of Independent Assortment: Alleles for different traits segregate independently of one another when sex cells are made.

 For Example: What happens if a man who is heterozygous brown eyes AND heterozygous tongue roller has children with a woman who is homozygous blue eyes AND heterozygous tongue roller?? What is the chance that their child will be a blue eyed non-tongue roller?

 Due to Mendel’s Law of Independent Assortment, we must look at all possible allele combinations that can go into sperm and egg. We will use a method of distribution you may have seen in math class called FOIL. FOIL stands for First, Outside, Inside, Last.

       

Foil the following genotype: BbWw (F) _____, (O) ______, (I) _____, (L) ____

Now we’re ready to tackle the example problem above.

What happens if a man who is heterozygous brown eyes AND heterozygous tongue roller has children with a woman who is homozygous blue eyes AND heterozygous tongue roller??

Dad’s Genotype: ____________

Possible Sperm Alleles: ______ or _______ or ______ or _______

Mom’s Genotypes: _____________

Possible Egg Alleles: ______ or _______ or _______ or _________

What is the chance their child will be a blue-eyed non-tongue roller?______ out of _____ or ______%

Dad: Homozygous blue eyes AND Heterozygous Widow’s Peak ____________

Mom: Heterozygous brown eyes AND Heterozygous Widow’s Peak ___________