Immunohematology
Genetic Inheritance
Genetic Terminology
Mendelean Genetics Terminology
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Dominant: Trait that is expressed in both the homozygous or heterozygous
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Recessive: Trait that is expressed only in the homozygous state (requires 2 recessive alleles for expression)
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Codominance: Both trait are expressed in the heterozygous state
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common in blood group inheritance like AB, Fy(a+b+)
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Dosage
Different levels of expression affect reaction to the antisera
Double dose: antigen expression is stronger in homozygous state
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Ex: SS
Single dose: Weaker reactions are seen with heterozygous
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Ex: Ss
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Common in Kidd, Duffy, MNSs blood groups
Pedigree Chart


What is a Pedigree Chart?
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How to read pedigree chart:
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Square: male & Circle: female
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Empty Square/Circle: Unaffected individual- the trait is not expressed
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Filled in Square/Circle: Affected individual- the trait is expressed
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Half-filled in Square/Circle: Carrier for trait but individual is unaffected
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Crossed out Square/Circle: Deceased individual
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Other Pedigree Chart Symbols

Consanguinous- related
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ie. siblings or cousins

Monozygotic- identical twins

Proband- (propositus)
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the patient of interest

Dizygotic- fraternal twins
Autosomal
Non-sex chromosomes (Chromosome 1-22 in humans)
Autosomal Dominant

Autosomal Recessive

Sex-Linked
Sex chromosome (23rd chromosome; XY in males XX in females)
X-linked Dominant

X-linked Recessive

Y-linked

Test Yourself
Sources:
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Hart, S. (2020). Pedigree. Retrieved September 02, 2020, from https://www.genome.gov/genetics-glossary/Pedigree
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John P. Hussman Institute for Human Genomics. Genetics Basics - Lesson 3: Modes of Inheritance. Genetics Basics Lesson 1: The basics of DNA and genetic disease, including phenotype and genotype. http://hihg.med.miami.edu/code/http/modules/education/Design/Print.asp?CourseNum=1.
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Nickle, T., & Barrette-Ng, I. (2020, August 15). 5.2: Inferring the Mode of Inheritance. Biology LibreTexts. https://bio.libretexts.org/Bookshelves/Genetics/Book:_Online_Open_Genetics_(Nickle_and_Barrette-Ng)/05:_Pedigrees_and_Populations/5.2:_Inferring_the_Mode_of_Inheritance.
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Walker, L. (2018) Blood Group Genetics [Powerpoint Slides]. Retrieved from UTMB Blackboard.
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Walker, L. (2020). Immunohematology Objective Review I [Powerpoint Slides]. Retrieved from UTMB Blackboard.
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