1. Terry Kotrla, MS, MT(ASCP)BB
Genetics
Terry Kotrla, MS, MT(ASCP)BB

2. Terminology Genes Chromosomes Locus Alleles Homozygous Heterozygous
Syntenic
Cis and Trans
Linked
Crossing over

3. Gene Basic unit of inheritance.
hold the information to build and maintain an organism's cells and pass genetic traits to offspring.

4. Chromosomes
organized structure of DNA and protein that is found in cells
46 total
23 homologous
22 autosomes
1 sex chromosome – X or Y
XX female
XY male

5. Chromosomes

6. Locus
Location of a gene on a chromosome

7. Homozygous or Heterozygous
Homozygous – both alleles the same
Heterozygous – alleles are different

8. Syntenic
two genetic loci have been assigned to the same chromosome but still may be separated by a large enough distance in map units that genetic linkage has not been demonstrated.

9. Linked or Genetic Linkage
Genetic linkage occurs when particular genetic loci or alleles for genes are inherited jointly.
Genetic loci on the same chromosome are physically close to one another and tend to stay together during meiosis, and are thus genetically linked

10. Crossing Over
Alleles at loci linked but sited at some distance from each other will often be separated by crossing over.
Crossing over happens at the first meiotic division of gametogenesis.
offspring that have different genetic make up from each other as well as different from either parent

11. Segregation
Alleles at loci which are carried on different chromosomes or at loci far apart on the same chromosome, and whose entry together into a sex cell is a matter of chance, are said to segregate independently.

12. Phenotype and Genotype
A phenotype is the assortment of antigens actually detectable on an individual's red cell.
Genotypes cannot be determined with certainty and can only be accomplished through family studies.

13. Genotype versus Phenotype
In example on left unless you knew parents type you would not know children’s genotype.
In example on right knowing children’s phenotype you can determine parents genotype.

14. Genotype
The mother in the first generation has the AB genes since her phenotype is AB.  
In the mating for the second generation, the genotype for the father could either be BB or BO since his father's phenotype is unknown.  It would appear the mother is AA since both her parents are A, but.....
Look at their children's blood types.  What is the mother's genotype now since both children are B?

15. Traits
Traits are the observed expressions of genes.

16. Dominant and Recessive
Dominant – gene present trait will be expressed
Recessive – trait will not be expressed unless present in a double dose

17. Traits

18. Blood Group Antigens Codominant
If the allele is inherited it will be expressed.
Zygosity does not matter.

19. Blood Groups
Genotypes A O AO

20. Blood Groups
Genotypes A O B AB BO AO OO

21. Parentage Testing Codominant traits are useful.
Two types of exclusions
Direct
Indirect

22. Direct Exclusion
Genetic marker present in child absent from mother and alleged father
Child A
Mother O
Father O
The A gene MUST have come from the “real” father as both parents are O.

23. Indirect Exclusion
Genetic markers are absent from the child that should be transmitted by the alleged father
Child Fy(a+b=) = Fya/Fya
Mother Fy(a+b=) = Fya/Fya
Father Fy(a=b+) = Fyb/Fyb
Child should have inherited Fyb from dad but it is not there.
Indirect because absence could be due to some rare Fy genes that cause suppression of expression. Dad may really be heterozygous Fy/fy and child inherited the fy gene making it appear homozygous.

24. Parentage Testing Direct exclusions much better.
DNA testing now the “gold standard”, very cheap and relatively fast.

25. Population Genetics
Important when attempting to find compatible blood.
Phenotype frequencies performed by testing a population and determining frequency of presence and absence of certain alleles.
Phenotype frequencies should be 100%
Jka+ = 77%
Jka- = 23%
23% of the population would be compatible for a patient with Jka antibodies.

26. Population Genetics Some patients have MULTIPLE antibodies.
Knowing the frequency of each allele allows one to calculate the number of units which would need to be screened to find compatible blood.
Performed by multiplying the percentages of each antigen negative allele.

27. Population Genetics The following frequencies are found: Antigen
Frequency of individuals negative c
20% (0.20) K
91% (0.91)
Jka
23% (0.23)
0.20 s 0.91 x 0.23 = 0.04 x100 = 4 out of 100 units

28. Exam 2 Online