1. GENETICS
BAD BOYS OF GENETICS: PATTERNS OF INHERITANCE WHICH DO NOT FOLLOW MENDEL’S RULES

2. BIG IDEA
Traits are inherited in a consistent pattern

3. OBJECTIVES
Compare and contrast the patterns of inheritance that do not follow Mendel’s rules.
Explain how traits are influenced by the environment.

4. X INTRODUCTION PREDICT: What will be the result if you cross…
A WHITE SNAPDRAGON
A RED SNAPDRAGON

5. INTRODUCTION
A PINK SNAPDRAGON!!!

6. INTRODUCTION BAD BOYS OF GENETICS
PATTERNS OF INHERITANCE WHICH DO NOT FOLLOW THE RULES ESTABLISHED BY MENDEL
These include…
INCOMPLETE DOMINANCE
CODOMINANCE
POLYGENIC TRAITS
MULTIPLE ALLELES
ENVIRONMENTAL EFFECTS

7. INCOMPLETE DOMINANCE Sometimes called “Blended Traits”
In organisms which follow complete dominance (or the rules set down by Mendel), the homozygous dominant (e.g. RR) and the heterozygous (e.g. Rr) would have the SAME PHENOTYPE
INCOMPLETE DOMINANCE: heterozygous individuals show phenotype that is in between the phenotypes of the two homozygous parents

8. INCOMPLETE DOMINANCE EXAMPLES Snapdragons Cholesterol
Red Flowering Plant x White Flowering Plant = PINK
RR x rr = Rr
Cholesterol
HH=can maintain healthy cholesterol levels
Hh=cholesterol level 2x as high as normal (1 in 500 people)
hh =cholesterol 5x as high (1 in million people)
Called HYPERCHOLESTEROLEMIA
Very serious condition, has even caused heart attacks in two-year-old children

9. CODOMINANCE EXAMPLES Palomino Roan cattle
Creamy-golden horse with pale mane and tail
Offspring of chestnut-colored horse and white horse
Roan cattle
Roan cows have coats that are primarily red with white hairs
Offspring of red cows and white cows

10. CODOMINANCE
CODOMINANCE: both alleles express themselves fully, and both phenotypes are visible
EXAMPLES
Chickens
Black feathered chicken homozygous for black (BB)
White birds also homozygous for white (WW)
If you cross black and white bird… BB x WW = BW
Result is chicken with a pattern of black and white feathers
Same thing with Belted Galloways
or “OREO COWS”

11. Belted Galloways “ OREO COWS”

12. CODOMINANCE EXAMPLES Human Blood Types
Blood types refer to the two different proteins (ANTIGENS) that coat the surface of red blood cells
Type A blood type = type A protein
Type B blood type = type B protein
Type AB blood type = type A and B proteins
Type O blood type = neither protein

13. POLYGENIC TRAITS
POLYGENIC TRAITS: traits controlled by two or more genes
EXAMPLE
Eye Color is determined by genes for…
TONE of pigment: color of pigment
AMOUNT of pigment: blue eyes have less
POSITION of pigment: eye pigment not distributed evenly, creating patterns

14. MULTIPLE ALLELES
So far, we have exclusively considered traits with only two alleles for A PARTICULAR GENE
Many traits have more than TWO alleles
MULTIPLE ALLELES: traits which have 3 or more alleles for that gene

15. MULTIPLE ALLELES Human Blood Type
Blood type is an example of codominance and MULTIPLE ALLELES
Blood types can be produced by 3 different alleles IA IB i
Phenotype Genotype
A IAIA or IAi
B IBIB or IBi
AB IAIB (codominance)
O ii
Thus, there are 4 blood types controlled by 3 blood type alleles = MULTIPLE ALLELES

16. ENVIRONMENTAL EFFECTS
We have seen how many factors can influence how a gene is expressed
Genes are also influenced by ENVIRONMENT (both internal and external)
INTERNAL:
Different HORMONES in males and females produce different environment in your body, and thus affect genes
FEATHERS of birds (males are often brightly colored)
HORNS of bighorn sheep (males are much heavier and coiled)

17. ENVIRONMENTAL EFFECTS
EXTERNAL
Hydrangeas: flowers BLUE in acidic soil, flowers PINK in neutral/somewhat basic soil
HIMALAYAN RABBIT
Normally covered with WHITE fur and eyes/nose/feet are BLACK
Extremities are COOLER than rest of body
Body temperature affects expression of GENE that controls fur color
If fur removed and patch is kept cool, as the fur grows back it will be BLACK
HUMAN HEIGHT: polygenic trait, also affected by nutrients in diet
Others:
Butterflies: some species show darker wings if butterfly born in spring, light in summer
Japanese Goby fish: change sex back and forth depending on presence of other fish and their sex

18. Sex-Linked Traits
Pattern of inheritance is located on the X-chromosome or the Y- chromosome
Y is much smaller
Therefore, there are more X-linked disorders/traits

19. What numbers to you See?

20. Ex. Colorblindness X-linked disorder Most common in ? Males (1/10)
Females (1/100)

21. X-linked Problems…
Hemophelia is a hereditary disease in which the blood does not clot. The allele for normal blood clotting is carried on the X chromosome.
1. A carrier female marries a hemophilic man. How many male children will have hemophilia? How many female children?
2. A normal woman whose father had hemophilia marries a normal man. What is the chance that their children will have hemophilia?
3. Todd is not colorblind. He is married to Ann whose father was red-green colorblind. Todd and Ann have 2 children, Ed is colorblind and lisa is not. What are the genotypes of Todd, Ann, Ed, and Lisa?

22. One male child with hemophilia (25%) and one female child with hemophilia (25%).
There is a chance that one male child with have hemophilia (25%).

23. Pandoras Box
pandoras box