Unit 4 Day 4- Variations on Mendel's Laws

Unit 4 Day 4- Variations on Mendel's Laws

By jack morgan

Multiple Choice

Mendel's First Law states that...

• Alleles are different versions of the same gene

• During Meiosis, the two alleles for a trait will separate

• During Mitosis, the two alleles for a trait will separate

• Alleles become dominant or recessive during Meiosis

Multiple Choice

Mendel's Second Law States that...

• Alleles are passed down from parents to offspring

• New Alleles develop from mutations or from crossing over

• Alleles on different chromosomes segregate independently of one another

• Dominant alleles on different chromosomes segregate as a unit

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The heterozygote expresses an intermediate trait, in between the Dominant and Recessive expression​

​ ex. C^RC^R --> Red Flower

C^WC^W --> White Flower

C​^RC^W --> Pink Flower

Variation 1: Incomplete Dominance​

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Open Ended

Discuss with your group: If two Heterozygous, Pink flowers were crossed with each other, what would the ratio of their offspring's Phenotypes be? (Hint: Use a Punnett Square to help you)

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​Both alleles affect the phenotype equally, and separately

• ​Both traits are seen

• there is no "Middle" phenotype

Variation 2​: Co-Dominance

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Open Ended

Discuss with your group: Do you think that Blood Type (the ABO system) is an example of Complete Dominance, Incomplete Dominance, or Co-Dominance? Why?

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• ​One gene controls multiple characteristics

  • Ex. Sickle Cell Anemia​

Variation 3: Pleiotropy​

A single characteristic is controlled by multiple genes

• ​Ex. Eye Color and Skin Color

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Variation 4: Polygenic​

• Natural skin colors are all due to differing levels of melanin ​

• Albinism occurs when the enzyme that produces melanin is non-functional ​

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Albinism: Not a skin color, but found on a single gene (aa)​

In many instances, Phenotype is determined by Genetics AND environment​

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Arctic Foxes coat color changes due to heat-sensitive alleles, so they turn brown in the summer and white in the winter​

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Skin color can change in the sun​

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​Nature vs Nurture

Multiple Choice

Which of the following is an example of Incomplete Dominance

• A Black Bear and a White Bear have an offspring that has spots

• A Red flower and a Blue flower produce a Purple Flower

• The Allele for Sharp Teeth also causes a fox to develop thicker bones

• A parent with Cystic Fibrosis and one without have 3 children, and two of them develop Cystic Fibrosis

Multiple Choice

Pleiotropy is when...

• Multiple Alleles control one trait

• One Allele controls one trait

• One Allele controls multiple traits

• An allele does not control any traits

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