ANTB15H3 Lecture Notes - Hemolytic Disease Of The Newborn, Globulin, Valentina Vostok

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8 Dec 2013
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Lecture 5, Oct 7, 2013- Evolutionary Change
Classical Genetic Markers
1. Simple inheritance (one gene)
2. No environmental modification
3. Easily scored and recognized
4. Vary from population to population (polymorphic 2 or more alleles in the
system) example: ABO blood group system
All classical genetic markers are Mendelian traits, but not all Mendelian traits make
good genetic markers
Little People Big World” (TLC)
The Roloff Family
Matt Roloff diastrophic dysplasia (autosomal recessive)
Amy Roloff (achondroplasia), son Zach (achondroplasia)
Achondroplasia
1/26,000 to 1/40,000 births
Autosomal dominant individual with achondroplasia has 50% chance (1 in 2)
of producing offspring with achrondroplasia
NOTE: carriers not possible the allele is either inherited or not if allele is
inherited, the trait will be expressed
Genetic counseling: scenario would shift if both parents have achondroplasia
50% chance achondroplasia, 25% chance average stature, 25% homozygous
achondroplasia (double dominant)
Est. 75% of cases born to average-size parents in these cases, “de novo
mutation” (spontaneous) has occurred
Achondroplasia tied to gene located on Chromosome 4 (75% spontaneous
mutation; 25% inherited) [reducing functioning of fibroblast growth factor
receptor 3]
1. Genetic Markers: Blood types & Disease
Some Basics of blood types and ABO distribution
Molecular Genetic Markers
2. Blood type incompatibility: Hemolytic disease of the newborn
Blood Types
Classic genetic markers
There are at least 60 Blood types that are polymorphic
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ABO, Rh, MNSs, Kell, Duffy, Lewis
There are some blood types that are considered to be ‘private’ restricted to a
family or small group of individuals, therefore useful for human genetics
MN system and S= MNS system
Gene loci closely linked on 4th chromosome
Therefore genes transmitted as Ns
No antibodies for MN system
The Duffy Blood Group
Two co-dominant genes for presence of antigen
natural selection in malaria prevalent areas
Fy4 antigen does not have attachment for vivax
Est. Degree of admixture of European and African descent
ABO Blood system
H- system: lays down a precursor substance. Allows you to make A, B, or AB
If you are homozygous (h/h), you will not display any of your blood type -> you’ll
simply be old
This particular genotype is called Bombay blood type, discovered in Bombay
Bombay blood Type
Can not create A.B or H antigens, therefore neither blood type A,B or O
Is a homozygote recessive condition= hh
Will have anti-H antibodies
Commonly found in Mohorati speakers in and around Bombay
North and South America: no B blood type
Most common is blood type O
Global Distribution of ABO blood types
Typically O is most common: 62.5%
A: 21.5%
B: 16%
However population specific, great diversity in range of frequencies. Why? Differential
in fertility and disease susceptibly= an evolutionary force operating???
Differential Fertility
Type B mothers have more offspring
Incompatibility of parental blood types:
Type O mothers x A or B fathers have fewer offspring
Type O mothers produce more O children than expected (>50%) because:
vagina may have anti-bodies for type A
anti-a and anti-b anti-bodies cross placenta and kills fetus
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