1. Complex Patterns of Heredity
Chapter 12

2. Sometimes Heredity Follows Different Rules
Dominant allele patterns
Incomplete Dominance: Appearance of a third phenotype
Codominance: Expression of both alleles
Multiple phenotypes from multiple alleles
Sex determination
Sex-linked inheritance
Polygenic Inheritance
Environmental Effects

3. Use the textbook to find out information about the following genetic patterns
Dominant Genetic disorders (pg 298)
Incomplete Dominance (pg 302)
Codominance (pg 302)
Multiple Alleles (pg 304)
Use two columns – fold paper in half lengthwise
right side – notes left side - examples

4. Incomplete Dominance
With incomplete dominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits. 
RED Flower x WHITE Flower ---> PINK Flower
The allele for red is not completely dominant over the allele for white

5. Codominance
The genetic gist to codominance is pretty much the same as incomplete dominance.  A hybrid organism shows a third phenotype --- not the usual "dominant" one & not the "recessive" one ... but a third, different phenotype. 
In COdominance, there are basically two “dominant” traits which appear together in the phenotype of hybrid organisms.

6. Codominance Cont
R = allele for red flowers W = allele for white flowers red x white ---> red and white spotted
RR x WW ---> 100% RW

7. Codominance Example red x white ---> red & white spotted
With codominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype in which both of the parental traits appear together.

8. Examples of Codominance
A very common phenotype used in questions about codominance is roan fur in cattle. 
Cattle can be red (RR = all red hairs), white (WW = all white hairs), or roan (RW = red & white hairs together). 
Another example of codominance is human blood type AB, in which two types of protein ("A" & "B") appear together on the surface of blood cells.

9. Multiple Alleles When a trait is controlled by Multiple Alleles
Controlled by 3 or more alleles of the same gene that code for a single trait
Ex. Blood types
A & B are codominant – both are expressed when together; and both are dominant to O.
A person can only have type O blood if they receive the “O” allele from both parents.

10. Multiple Phenotypes from Multiple Alleles
Although each trait that we have studied so far only has two alleles, it is common for more that two alleles to control a trait in a population
For instance, Pigeons – three colors possible (red, blue, chocolate)
However, each pigeon can have only two of these alleles

11. Blood Types Codominance and Multiple Alleles
Human blood is separated into different classifications because of the varying proteins on the surface of blood cells.
These proteins are there to identify whether or not the blood in the individual's body is it's own and not something the immunity system should destroy.

12. ABO Blood type and genetics Codominance and Multiple Alleles
The proteins (antigens) that are present on the surface of the cells are controlled by three alleles
A, B, o
The individual's blood type is determined by which combination of alleles he/she has.
Type A – AA or Ao
Type B – BB or Bo Type AB – AB Type O - oo
Blood types A and B are codominant alleles.
AB – both antigens present
O is the recessive allele
No antigens present

13. Human Blood Types

14. Human Blood Types

16. Blood type practice Use a Punnett Square!
A woman has type A blood. Her father has type O blood. The woman marries a man with type O blood. What is the chance that they will have a child with type A blood?
What is the chance that the couple from question 1 will have a child with type AB blood?
*Show me your answers when you are finished. Keep these in your notes!

17. Simple Dominant Heredity
Traits controlled by a Single Allele
More than 200 human traits are determined by a single dominant allele
Ex. Huntington’s Disease
More than 250 other traits are determined by homozygous recessive alleles
Both parents must have this allele in order for their offspring to have the disease.
Ex. Cystic Fibrosis & Sickle cell anemia

18. Comparison Inheritance Patterns
Recessive Allele Inheritance Patterns
Unaffected parents can have affected offspring
The phenotype can skip a generation
Carriers - Individuals with no signs of the trait but carry the allele (Tt)
Dominant Allele Inheritance Patterns
Affected offspring must have at least one affected parent, there are no carriers for the trait.
The phenotype appears in every generation without skipping
Two unaffected parents have no affected offspring

19. Polygenic traits
A trait that is controlled by a groups of genes. Polygenic traits are controlled by two or more genes at different locations on different chromosomes.
Examples are height, skin color and weight. Polygenes allow a wide range of physical traits.
For instance, height is regulated by several genes so that there will be a wide range of heights in a population.

22. Eye Color Activity

23. Sex determination
Remember that in humans the diploid number of chromosomes is 46, or 23 pairs.
There are 22 matching pairs of homologous chromosomes called autosomes.
The 23rd pair differs in males and females, they determine the sex of an individual (sex chromosomes)
X females (XX)
Y males (XY)
Complete a punnett square to determine the expected ratio of males to females produced given their possible gamete contribution

24. Sex-linked inheritance
Traits controlled by genes located on sex chromosomes are called sex-linked traits
Thomas Hunt Morgan discovered this pattern of inheritance

25. Patterns of Inheritance
Sex-Linked Traits
Are found only on the X chromosome
Ex. Colorblindness (recessive)
Ex. Hemophilia (recessive)

26. Pedigrees
Pedigree – a family record that shows how a trait is inherited over several generations.
Scientists often study disease causing genes because they can easily be traced

27. Patterns of Inheritance
Sex-Influenced Traits
Influenced by male or female sex hormones
Ex. Patterned Baldness
Homozygous baldness-both will lose hair
Heterozygous-men will lose hair but women will not

28. Pedigrees Cont.
Square = Male
Circle = Female
No shading = normal
Shaded = displays trait
Half/Half = Carrier
Carriers – Heterozygous; they do not express the recessive allele, but they pass it along to their offspring.

29. A Pedigree of Hemophilia in the Royal Families of Europe

30. Human Karyotype

31. Things to look for in pedigrees
Autosomal recessive disorders (rr)
males and females have the disorder
equally and can be carriers
can skip generations
Autosomal dominant disorders (Hh)
males and females could have the disorder equally, no carriers
will appear in every generation
Sex-linked recessive disorders (X CXc XCY)
males are more likely to have disorder
only female carriers

32. Environmental Effects
Genes are inherited from parents, but sometimes their expression is modified by environmental factors.
An example is the snowshoe hare we discussed earlier in the year-these hares have dark fur in the summer and white fur in the winter.

33. Epigenetics
Watch the video and record a few notes on what epigenetics is.

34. Snowshoe Hare
What causes the change in coat color in these rabbits?

35. Nondisjunction
Nondisjunction is the failure of homologous chromosome pairs to separate properly during meiosis. The result of this error is a cell with an abnormal (too few or too many) number of chromosomes.

36. Nondisjunction

37. Patterns of Inheritance
Disorders due to Nondisjunction
Monosomy (45 Chromosomes)
Trisomy (47 Chromosomes)
Trisomy-21 (Down’s Syndrome)
Klinefelter’s (XXY)-male w/ some female traits
Turner’s (XO)-female appearance
Single Y chromosome do not survive

38. Detecting Human Genetic Disorders
Genetic Screening – examination of genetic makeup
Karyotype: a picture of chromosomes grouped in pairs and arranged in sequence.
Screening of Blood: look for certain proteins
Genetic Counseling-medical guidance informing of problems that could affect their offspring.

39. Human Karyotype

40. Detecting Human Genetic Disorders
Amniocentesis: removal of small amount of amnionic fluid surrounding the fetus
Chorionic Villi Sampling: tissue that grows between the mother’s uterus and the placenta (between the 8th and 10th week)
Screening Immediately after Birth:
Ex PKU (Phenylketonuria)-body cannot metabolize the amino acid phenylalanine
Special diet lacking phenylalanine

41. Karyotyping