1. Non-Mendelian Genetics
Other Patterns of Inheritance

2. Mendel’s Principles
Inheritance of biological characteristics is determined by individual genes, which are passed on from parents to offspring
When two or more alleles exist for a trait some alleles will be dominant and others will be recessive
Most sexually reproducing animals carry two copies of their genes, one from each parent. Genes segregate from each other during meiosis
Alleles for different genes usually segregate independently from each other

3. Sometimes life is just a little more complicated….

4. Incomplete Dominance
Complete dominance – one allele completely dominates the other allele
Incomplete dominance – neither allele completely dominates
Heterozygous phenotype is a BLEND between the two traits
For example RED allele
and WHITE allele together make PINK flowers

5. Incomplete Dominance: P1: Red X White (the F1’s are all PINK)
Use TWO DIFFERENT capital letters
RR = red; WW = white; RW = Pink

6. R W R RW RR W Incomplete Dominance RW F2 Generation
1 Red: 2 PINK: 1 White R W R RR RW W RW WW

7. Codominance
When both alleles for a trait are expressed in a heterozygous offspring
Neither allele is dominant but phenotype is not a BLEND, both alleles are expressed at the same time
For example if the red and white allele in flower color was codominant instead of incompletely dominant then the heterozygous flowers would not be PINK they would be a mix of red and white

8. Codominance: ROANS R = red coat color W= White coat color
RW = ROAN Coat
Either the horse looks “speckled” because the white hairs are mixed in with the red hairs or it has patches of both colors
Both are expressed at the same time
NO BLEND

9. Multiple Alleles
Sometimes there are 4 or more phenotypes for a particular trait
This can only occur if there are more than 2 alleles
What we call multiple alleles
Humans have four blood types (A,B,AB,O)..Called the ABO Blood Group

10. Human blood type is controlled by three alleles: A, B and O
Human blood type is controlled by three alleles: A, B and O. Therefore human blood is controlled by multiple alleles
A and B are completely dominant over O
A and B are codominant

11. How do I know my blood type?
Our blood cells produce glycoproteins on their outercoats….
These are specific antigens (something that elicits an immune response) found on the RBC
Your blood is mixed with antiserum, something that causes an immune response
If your blood clots with a given antibody then you have that blood type
Blood Types Tutorial

12. Rh factor Known as the Rhesus factor…for the Rhesus monkey
Protein found on the surface of blood cells
Like the other proteins (A, B) found on the red blood cells
If you have the Rh factor you are Rh +; If you don’t you are Rh –
This is the +/- that goes with your blood type

13. Issues…
If a mother is Rh – and her baby is Rh + there can be complications in the pregnancy
Her body will create an immune response against the baby’s blood if their blood mixes
This can lead to: Miscarriage, Ectopic pregnancy, Blood transfusion
Erythroblastosis fetalis
This can be prevented with a treatment of RhIG..
Prevents sensitization to Rh + blood

14. Single gene may affect multiple phenotypes
Pleiotropy – Ability of a single gene to have multiple effects on different traits
Example: Phenylketonuria and sickle cell anemia
Epistasis – Alleles of one locus can prevent or mask the expression of alleles on a different locus
Examples: Coat color on Labradors

16. Polygenic Traits Some traits are controlled by several genes at once
Normally the phenotype is the result of the cumulative effect of all of these genes
Examples
Human height, Human skin tone
When the number of individuals in a population is plotted against the amount of pigmentation/height you create a normal distribution curve (bell curve)

18. Genes and the Environment
The phenotype of an organism is only partly determined by its genotype
Variables such as light, temperature and nutrition can affect phenotypes
Himalayan rabbits produce darker fur in colder temperatures…. If it warmer they keep their normal white fur

19. The environment can also create a phenotype that is similar to a phenotype that resembles a genetic trait
Known as Phenocopy
May occur within a family and seem to be inherited
Example: Butterflies that can change color and Fruit flies can develop yellow bodies by being fed silver salts