1. Incomplete dominance Co-dominance Sex-Linked Dihybrid Crosses
Types of Inheritance
Incomplete dominance
Co-dominance
Sex-Linked
Dihybrid Crosses

2. Incomplete Dominance There are 2 dominant genes
Both represented with capital letters
There are 3 possible phenotypes that result eg red, white and pink

4. Co-dominance
There are 2 dominant genes that are both expressed in the offspring
Results in NO new phenotype but rather both are expressed

5. Blood Groups An example of co-dominance Both A and B are dominant
Only o is recessive
AB blood group has both dominant genes
Blood type genotypes:
Type A – AA or Ao
Type B – BB or Bo
Type AB – AB
Type o - oo

6. Genetics of Blood Types
Your blood type is established before you are BORN, by specific GENES inherited from your parents.
You inherit one gene from your MOTHER and one from your FATHER.
These genes determine your blood type

7. How common is your blood type?
46.1%
38.8%
11.1%
3.9%

9. There are four basic blood groups:
Group A with A antigen on the red cells and anti-B antibodies in the plasma.
Group B with B antigen on the red cells and anti-A antibodies in the plasma.
Group AB with both A and B antigens on the red cells and neither anti-A nor anti-B in the plasma.
Group O with no A or B antigens on the red cells and both anti-A and anti-B antibodies in the plasma.
If you are a Group A person, you do not carry antibodies against A markers. But you do have antibodies against Group B blood.
If you are a Group B person, you have antibodies against Group A cells.
If you are a Group O, you have antibodies against both Group A and B!
The antibody reaction that occurs when two different blood groups are mixed, causes the foreign red cells to be destroyed (hemolysis). This can lead to kidney damage and death. That is why matching blood groups between donor and patient is so important before a transfusion is given.

10. ABO blood groups

11. SEX CHROMOSOMES Humans have 23 pairs of chromosomes.
One pair is responsible for determining the sex of the offspring.
These chromosomes are called the sex chromosomes. There are two types - X and Y.
XX - Female
XY -Male
Sperm cells can contain either a X or a Y chromosome, plus 22 others. Ova only contain X chromosomes, plus 22 others.
All offspring get an X chromosome from their mother.
It depends on which chromosome the father's sperm cell is carrying - X or Y - as to whether the baby is a boy or a girl.

12. Sex Linked Genes
Certain characteristics in humans are linked to the sex chromosomes.
Sex linkage affects are seen mainly in males. The reason for this is that X and Y chromosomes are different sizes. There area number of genes on the X chromosome that have no equivalent on the smaller Y chromosome, like colour vision and blood clotting.

13. Colour Blindness Normal Colour Red-Green Colour Blindness
Blue-Green Colour Blindness

14. Left Right Top 25 29 Spots Middle 45 56 Bottom 6 8
What numbers do you see revealed in the patterns of dots?
Normal Color Vision
Red-Green Color Blind
Left
Right
Top 25 29
Spots
Middle 45 56
Bottom 6 8

15. The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots.

16. Sex Linked Crosses
Example: In human's, Howard's disease weakens victims to be almost totally uncoordinated. Howard's disease is recessive and carried on the X chromosome only. Complete the following cross. A father who does not have the disease with a female who is a carrier of the disease.
Answer:
Male: XHY- Female: XHXh
1/4 25% homozygous normal female
1/4 25% carrier normal female
1/4 25% normal male
1/4 25% Howard's Disease male

17. Dihybrid Crosses
Where 2 traits are considered together due to their location on the chromosome they are inherited together
Each parent has 4 alleles of interest and will give 2 alleles to each offspring.

18. Dihybrid Crosses
Example: In doves the gene for plain wing colour is dominant over the gene for speckled, and the gene for light grey wings is dominant over the gene for white wings. Cross the following parents to find out the possible outcomes for their offspring.
The father of the offspring is heterozygous for both traits. The mother is homozygous speckled and heterozygous grey.
Answer:
Male: SsGg Female: ssGg
Possible genes to be passed are:
Male: SG, Sg, sG, sg Female: sG, sg, sG, sg sG sg SG
SsGG
SsGg Sg
Ssgg
ssGG
ssGg
ssgg
SsGG 1/8 12.5% Heterozygous plain, homozygous grey winged
SsGg 2/8 25% Heterozygous plain, heterozygous grey winged
ssGG 1/8 12.5% Homozygous speckled, homozygous grey winged
ssGg 2/8 25% Homozygous speckled, heterozygous grey winged
Ssgg 1/8 12.5% Heterozygous plain, homozygous white winged
Ssgg 1/8 12.5% Homozygous speckled, homozygous white winged

20. A 9:3:3:1 ratio is the standard result for a dihybrid cross
Epistasis
non-epistasis
mouse coat color
explanation
A 9:3:3:1 ratio is the standard result for a dihybrid cross

21. Normal dihybrid ratio is altered from 9:3:3:1 to
Epistasis
non-epistasis
mouse coat color
explanation
Epistasis
Normal dihybrid ratio is altered from 9:3:3:1 to
9:3:4:0
C/c gene is epistatic to the B/b gene