1. Mendel Genetics, Part 2 Co-dominance and Intermediate traits

2. Quick reteach of important concepts
Genes—DNA code sections to do/make a particular job or characteristic. Made of 2 parts. Alleles—a different version of the same genes. Example: Brown, Blonde hair

3. Quick reteach of important concepts
Phenotype—what the plant/animal looks like, based on its Genotype for that trait. Genotype—The letters that represent the Genes. Caps for Dominant, lower-case for Recessive

4. Quick reteach of important concepts
Heterozygous Alleles—2 DIFFERENT alleles Ex: Gg, or Tt, or Ss Homozygous Alleles—2 SAME alleles Ex: GG, or tt, or SS, or VV

5. What is Intermediate Inheritance?
SOMETIMES it is possible for genes to blend together to create new phenotypes (appearances) that are neither Dominant nor Recessive.

6. What is Intermediate Inheritance?
These blended traits are considered Intermediate Inheritance, and are the result of gene-blending by Co-dominance.

7. Intermediate Inheritance/alleles
Intermediate Inheritance, is a ‘new’ phenotype that is created when 2 alleles cannot completely dominate each other. Either by Codominance or Incomplete Dominance

8. Intermediate Inheritance/alleles
Intermediate Inheritance is caused by Co- dominance in genes/alleles. (prefix ‘co’ = 2 together)

9. Intermediate Inheritance/alleles
Co-dominance means that sometimes there are more than 1 Dominant gene for the same trait. If you receive 2 co-dominant alleles, they could blend together to create a new phenotype because neither dominates the other.

10. Intermediate Inheritance example
Example: Mice hair color genes have a co-dominance with Black and White—meaning that BOTH black and white are dominant alleles. Brown is the recessive allele in these mice.

11. Intermediate Inheritance example
If a mouse’s genotype is heterozygous Black and White, these 2 co-dominant genes will blend together and create a mouse with a grey phenotype.

12. Intermediate Inheritance example
In Mice, the grey phenotype is considered an Intermediate Trait because its phenotype is neither truly dominant or recessive, but rather a blend.

13. Intermediate Inheritance example 2
Some flowers are Red and White, and if cross- pollinated will produce heterozygous Pink offspring. If the pink flowers are crossed, then the offspring will be either Red or White again. (incomplete dominance)

14. Intermediate Inheritance example 2
Other Flowers, like petunias, when crossed will create new phenotypes that contain both colors from both parents. (Co-dominance)

15. Intermediate Inheritance example 3
Red Hair is the blending of red pigment pheomelanin into another hair pigment called eumelanin (the brown hair pigment)
The ‘more red’ a person’s hair is, the more pheomelanin and less eumelanin there is.
Darker red/brown hair has more eumelanin, and less pheomelanin

16. Intermediate example 4
Example 2: Green and Hazel Eyes The genes that create brown and green eyes are co-dominant Blue eyes are Recessive If you have heterozygous alleles of Brown and Green, the 2 genes will blend, creating hazel eyes

17. Intermediate Inheritance/alleles
If Green and Blue are heterozygous paired genes, the green will dominate the blue gene, and the person will have green eyes. Remember that the ‘true’ eye color is actually a mix of several genes working together (polygenetic traits)

18. Intermediate Inheritance example 2
Blood types A and B types are both Dominant blood type alleles. Type O is recessive. AB blood type is a blend of A and B codominance.

19. Intermediate Inheritance—How it works
Ex: Andalusian Chickens come in Black, White, or ‘Blue’.
White and Black Colors are co- dominant with each other in this species.

20. Intermediate Inheritance—How it works
“Blue” is the intermediate trait, created when a Black Color allele and a White color allele are combined and blended, unable to completely dominate each other.

21. Intermediate Inheritance Genotype
When writing these Intermediate alleles, the “C” for Color is used.
With the “C”, a superscript “W” or “B” is used to show which Intermediate alleles it has.

22. Intermediate Inheritance—How it works
CwCw = White CBCB = Black
CBCw = Blue chicken Tasty Chicken…

23. Intermediate Inheritance Punnett Squares
A Punnett Square testcross is the same as a Mono- hybrid cross, but when analyzing the results, you need to look more carefully.

24. Intermediate Test-cross (punnett square)
Mr. Vogel has Blood Type B. There is no type O in his family, So he is probably homozygous Type B Mrs. Vogel is Type A, with some type O (recessive allele) so her genotype is probably heterozygous A and O Both A and B are co-dominant alleles, but O type is recessive. What are the possible outcomes of their children's’ blood type?

25. Intermediate Test-cross (punnett square)
What are the Genotypes? Blood Type Genotypes Type A = TATA or TA t Type B = TBTB or TB t Type O (recessive) = t t Type AB (intermediate) = TATB

26. Intermediate Test-cross (punnett square)
Step 1: make the square

27. Intermediate Test-cross (punnett square)
Step 2: create the genotypes: T will be used for blood Type Mr. V is homozygous B—so the genotype is TBTB

28. Intermediate Test-cross (punnett square)
Step 2: create the genotypes: Mrs. V. is Heterozygous A and recessive O, so the genotype is TA t. (t = the recessive blood type allele)

29. Intermediate Test-cross (punnett square)
Step 3: add the genes to the square, and do the test- cross, like normal

30. Intermediate Test-cross (punnett square)
Note: if you see genotypes with both dominant traits, then they will be blended.

31. Intermediate Test-cross (punnett square)
So, the outcomes of blood types are… _____% A _____% AB _____% B ______% O

32. Intermediate Test-cross (punnett square)
So, the outcomes of blood types are… AB = 50% Type B = 50%
Type AB
Type AB
Type B
Type B

33. Intermediate Test-cross 2 (punnett square)
Snapdragons are co-dominant red and white. If these genes are combined, then they produce pink flowers. What % of the offspring would be white if 2 Pink parents are crossed?

34. Intermediate Test-cross 2 (punnett square)
Step 1 – make square Step 2: create genotypes: --C for Color is used. --Pink is a blend of red and white so a pink’s genotype must be CRCW.

35. Intermediate Test-cross 2 (punnett square)
Step 3: add the genes to the square and do the test- cross. According to the data ____% of the offspring will be white, and ____% will be red.

36. Polygenic Inheritance
Many traits are NOT determined
by 1 set of 2 alleles alone.
Some phenotypes, like tallness, and ‘true’ eye appearance are considered Polygenic, or created from more than 1 set of genes.

37. Polygenic Inheritance
Ex: Height
A person’s height may
be determined by
multiple characteristics
each controlled by
separate genes
Length of leg-bones (femurs)
Length of torso/vertebrate
Length of neck.

38. Polygenic Inheritance
Since these characteristics all have their own Genotype, and are all combined to make a person’s total height, Height would be a Polygenic trait.

39. Polygenic Inheritance and the environment
Many of these traits may be affected by their environments/diets as well.

40. Polygenic Inheritance and the environment
Ex 1: a person’s polygenic genotype may say that this person should be very tall, but a lack of proper nutrition may keep the person shorter than they could be.
Fakes
A ‘giant’s’ revolver ?

41. Polygenic Inheritance and the environment
In Medieval Times, a constant, varied supply of good food was basically impossible for people to have.

42. Polygenic Inheritance and the environment
People back then had genes to be as tall as people today, but the lack of proper diet did not give their bodies the nutrition needed to grow to their maximum.
Sir William Wallace

43. Polygenic Inheritance and the environment
A 5ft 5 inch male, which is an average height today, was considered very tall 100s of years ago.