1. 7/4/2019
Today’s Agenda…
Bellringer: Identify the following as homozygous or heterozygous:
A. TT
B. Ww
C. yy
D. Ss
Notes on Genetics Since Mendel #12
Worksheet for Homework
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2. February 16th Study Pack #12 Page 314
Genetics
Since
Mendel
February 16th
Study Pack #12
Page 314

3. 7/4/2019
Today’s Goals…
I can explain how traits are inherited by incomplete dominance.
I can compare multiple alleles and polygenic inheritance, and give examples of each.
I can explain how the gender of offspring is determined.
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4. Unexpected Results After Mendel scientists did more work with genetics
7/4/2019
Unexpected Results
After Mendel scientists did more work with genetics
Four o’clock plants
Crossed purebred red-flowered plants with purebred white flowered plants
Expected to get all red flowers
Instead all the flowers were pink!
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5. Unexpected Results Neither allele for flower color was dominant
7/4/2019
Unexpected Results
Neither allele for flower color was dominant
An intermediate (middle) phenotype was produced - pink flowers
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6. 7/4/2019
Incomplete Dominance
When two parents combine to create a middle phenotype it is called incomplete dominance
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7. 7/4/2019
Incomplete Dominance
Page
Palomino Horses

8. Multiple Alleles Mendel studied traits that had just two alleles
7/4/2019
Multiple Alleles
Mendel studied traits that had just two alleles
A trait can have multiple alleles
Multiple alleles produce more phenotypes of a trait
If you have three different alleles, imagine all the combinations possible
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9. Multiple Alleles Example: Blood Type The alleles are A, B, O
7/4/2019
Multiple Alleles
Example: Blood Type
The alleles are A, B, O
O is recessive to A and B
When a person inherits both A and B, they have bloodtype AB
4 phenotypes possible: A, B, AB, 0
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10. Polygenic Inheritance
7/4/2019
Polygenic Inheritance
Polygenic Inheritance occurs when a group of gene pairs acts together to produce a trait
This produces a wide variety of phenotypes
Examples: Height, shades of eye and skin color
3-6 gene pairs control your skin color and more may control your hair and eye color
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11. Polygenic Inheritance
7/4/2019
Polygenic Inheritance
Your environment can also play a role in your traits
Environmental factors can be internal or external
Chemicals in the body of some birds cause them to be more brightly colored
A person who is at risk for skin cancer can avoid the sun
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12. Polygenic Inheritance
7/4/2019
Polygenic Inheritance
What environmental factors might affect the size of leaves on a tree?
Amount of water or sunlight available
Chemicals in the soil
Temperature and weather conditions
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13. 7/4/2019
Compare
What is the difference between multiple alleles and polygenic inheritance?
Polygenic Inheritance involves many GENES as opposed to many forms of the same gene
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14. Gender Determination One pair of chromosomes determines gender
7/4/2019
Gender Determination
One pair of chromosomes determines gender
In females, they are labeled as XX
In males, they are labeled as XY
The chromosomes received from the mother and the father determine the gender of the offspring
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15. Homework Worksheet – Genetics Challenge 7/4/2019
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