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Genetics in HumansGenetics in Humans
Marie ČernáMarie Černá
Monogenic inheritance Monogenic inheritance (Mendelian genetics) – 1%(Mendelian genetics) – 1%
– single gene
For each gene, an organism inherits two alleles, one from each parent
• Homozygous – having two identical alleles for a gene• Heterozygous – having two different alleles for a gene
in the phenotype of a heterozygote:• dominant allele – is fully expressed• recessive allele – is completely masked
Monogenic inheritance Monogenic inheritance (Mendelian genetics) – 1%(Mendelian genetics) – 1%
• complete dominance: phenotype # genotype
• incomplete dominance: phenotype = genotype
• codominance (blood group):phenotype = genotype
Polygenic inheritance Polygenic inheritance (multifactorial) – 99 %(multifactorial) – 99 %
– many genes– environmental effect on phenotype
• quantitative characters• Gaussian distribution
Gaussian distributionGaussian distribution
ABABOO blood group blood groupss
ABABOO blood group blood groupss
ABO blood groupABO blood groupss
Frequencies (%) of blood group system Frequencies (%) of blood group system in the U.S.A. populationin the U.S.A. population
Blood group
Blood antigen
Antibody in serum
White Caucasians
Blacks Asians American Indians
O H anti-A,B 45 49 40 79
A A anti-B 40 27 28 16
B B anti-A 11 20 27 4
AB AB - 4 4 5 1
Rh blood groupRh blood group
Rh blood groupRh blood group
Rh blood groupRh blood group
Blood group donors and recipientsBlood group donors and recipients
LiteratureLiteratureBiology, eighth edition,Campbell, Reece
Unit three: GeneticsChapter 14: Mendel and the Gene IdeaConcept 14.3: Inheritance patterns are
often more complex than predicted by simple Mendelian genetics
Pages 271 – 275