ABO blood groups Multiple alleles ABO blood group

ABO blood groups

Multiple alleles ABO blood group s Table 14. 2 There are 3 different alleles, IA, IB, and i Allele IA makes a cell surface antigen, symbolized with a triangle IB makes a different antigen, symbolized as a circle i makes no antigen

Multiple alleles ABO blood group s Human ABO Blood Groups • Gene “I” specifies which sugar is found on the outside of red blood cells • 3 alleles are present in the human population: • IA = N-acetyl-galactosamine • IB = galactose • i (also referred to as o) = no sugar present • 6 possible genotypes

Multiple alleles ABO blood group s Immunology 101 • Sugar on the blood cell is an antigen* (A, B, A and B, or none) • Your immune system thinks your own antigens are fine • Your immune system makes antibodies against non-self antigens • Antibodies recognize and target cells with antigens for destruction *something that elicits an immune response

Multiple alleles ABO blood group s The Human ABO Blood Group System

Multiple alleles ABO blood group s The Human ABO Blood Group System multiple alleles codominance

Multiple alleles ABO blood group s Codominance in the Human ABO Blood Group System Dominance Codominance

Sex linked inheritance Sex-linked traits are produced by genes only on the X chromosome. They can be Dominant or Recessive. A = dominant a = recessive What would be the genotypes of a male and female that have a Sexlinked Dominant trait and do not express the trait? Expresses Trait: Male - XA Y Female - XA XA or XA Xa No Expression: Male - Xa Y Female - Xa Xa What would be the genotypes of a male and female that have a Sexlinked Recessive trait and do not express the trait? Expresses Trait: Male - Xa Y Female - Xa Xa No Expression: Male - XA Y Female - XA XA or XA Xa (Carrier) Most Sex-linked traits are Recessive!

• Gene located on the X chromosome • More males than females affected (males inherit X from mother) • Females can only inherit if the father is affected and mother is a carrier (hetero) or affected (homo) • An affected female will pass the trait to all her sons – Daughters will be carriers if father is not affected • Males cannot be carriers (only have 1 X so either affected or not) • Can skip generations (hide) • E. g. color blindness, hemophilia, Duchene muscular dystrophy

Sex Linked Problems: • Red-green color blindness in men is caused by the presence of a sex-linked recessive gene c, whose normal allele is C. a) Can two color blind parents produce a normal son? b)Can they produce a normal daughter? c) Can two normal parents produce a colorblind son or daughter? d)Can a normal daughter have a colorblind father or mother? e)Can a colorblind daughter have a normal father or mother?

Sex influenced traits • A phenotypic characteristic or trait that is expressed differently in males and females – male pattern baldness

How to Construct a Pedigree • A Pedigree is a visual showing the pattern of inheritance for a trait. (Family tree) • • Symbols and Rules: Male = Female = Affected = Unaffected = Carrier = Link parents together with a line and then make a vertical line to connect to offspring.

Autosomal Dominant Pedigree • Draw a Pedigree showing a cross between Heterozygous parents that have 2 boys and 2 girls. (Show all possibilities) Genotypes of Affected and Unaffected: • AA and Aa = Affected aa = Unaffected Aa aa Aa AA

Autosomal Recessive Pedigree • Draw a Pedigree showing a cross between Heterozygous parents that have 2 boys and 2 girls. (Show all possibilities) Genotypes of Affected and Unaffected: • AA=Unaffected Aa=Carrier, Unaffected aa=Affected Aa aa Aa AA

Sex-Linked Recessive Pedigree • Draw a Pedigree showing a cross between a Red eyed Male fruit fly and a Carrier Female fruit fly which have 2 males and 2 females. (Show all possibilities) Red is dominant to white. • Genotypes of Parents: • Male = XR Y Female = XR Xr XR Y XR Xr Xr Y XR XR XR Xr

Characteristics of Autosomal Dominant, Autosomal Recessive, and Sex-linked Recessive Traits • In groups, analyze your notes on each type of disorder and examine the pedigrees. • Come up with rules/characteristics for each type of Trait.

Autosomal Dominant Traits • Heterozygotes are affected • Affected children usually have affected parents. • Two affected parents can produce an unaffected child. (Aa x Aa) • Two unaffected parents will not produce affected children. (aa x aa) • Both males and females are affected with equal frequency. • Pedigrees show no Carriers.

Autosomal Recessive Traits • Heterozygotes are Carriers with a normal phenotype. • Most affected children have normal parents. (Aa x Aa) • Two affected parents will always produce an affected child. (aa x aa) • Two unaffected parents will not produce affected children unless both are Carriers. (AA x AA, AA x Aa) • Affected individuals with homozygous unaffected mates will have unaffected children. (aa x AA) • Close relatives who reproduce are more likely to have affected children. • Both males and females are affected with equal frequency. • Pedigrees show both male and female carriers.

Sex-Linked Recessive Traits • More males than females are affected. • An affected son can have parents who have the normal phenotype. (XAY x XAXa) • For a daughter to have the trait, her father must also have it. Her mother must have it or be a carrier. (Xa. Y, Xa. Xa, XAXa) • The trait often skips a generation from the grandfather to the grandson. • If a woman has the trait (Xa. Xa), all of her sons will be affected. • Pedigrees show only female carriers but no male carriers.

Polygeny Polygenic inheritance: additive effects (essentially, incomplete dominance) of multiple genes on a single trait AA = dark Aa = less dark aa - light And similarly for the other two genes - in all cases dominance is incomplete for each gene. Think of each “capital” allele (A, B, C) as adding a dose of brown paint to white paint.

Environmental effects • environment often influences phenotype • the norm of reaction = phenotypic range due to environmental effects • norms of reactions are often broadest for polygenic characters. Blue require low p. H

Environmental effects: effect of temperature on pigment expression in Siamese cats