ABO blood groups. Table 14.2 Multiple alleles ABO blood group s There are 3 different alleles, I A,...
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Transcript of ABO blood groups. Table 14.2 Multiple alleles ABO blood group s There are 3 different alleles, I A,...
Table 14.2
Multiple allelesABO blood group s
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
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 allelesABO 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 allelesABO blood group s
Codominance in the Human ABO Blood Group System
Dominance
Dominance
Codominance
Multiple allelesABO blood group s
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 Sex-linked 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 Sex-linked 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!
Sex linked inheritance
• 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 AAaa
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=AffectedAa Aa
Aa Aa AAaa
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
XRY XRXr
XRY XrY XRXR XRXr
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. (XaY, XaXa, XAXa)
• The trait often skips a generation from the grandfather to the grandson.
• If a woman has the trait (XaXa), all of her sons will be affected.
• Pedigrees show only female carriers but no male carriers.
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.
Polygeny
• 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 pH
Environmental effects
Environmental effects: effect of temperatureon pigment expression in Siamese cats
Environmental effects