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Blood Group Notes
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IB Assessment Statement
Describe ABO blood groups as an example of codominance and multiple alleles. Phenotype Genotype O ii A IAIA or IAi B IBIB or IBi AB IAIB
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Codominance In the cases of some genes, two alleles may be expressed in the phenotype at the same time. That is, NO allele is truly dominant or recessive.
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Codominance When no alleles are dominant in a gene, we say these alleles are codominant. Example: If a homozygous white rose (WW) is crossed with a homozygous red rose (RR) all their offspring are pink (WR). That ism they show a blending of physical traits.
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Blood Type. There are three alleles for blood type:
Blood Group B represented by IB co-dominant with blood group A Dominant over blood group O Blood Group A represent by IA co-dominant with blood group B Blood Group O represented by i Recessive to both group A and B
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Practice Cross 1 : A person with homozygous Group A blood crosses with a homozygous Group B Blood: The Symbols (letters you will use) ______________________ The Cross (the parent’s genotypes)_________________________ The Punnett square:
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Practice Cross 2: A person with heterozygous Group AB blood crosses with another heterozygous Group AB Blood: The Symbols (letters you will use) ______________________ The Cross (the parent’s genotypes)_________________________ The Punnett square:
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Practice Cross 3: A person with heterozygous Group AB blood crosses with a person who has O type Blood: The Symbols (letters you will use) ______________________ The Cross (the parent’s genotypes)_________________________ The Punnett square:
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Practice Cross 4: A person with heterozygous Group A blood crosses with a person who is heterozygous with B type Blood: The Symbols (letters you will use) ______________________ The Cross (the parent’s genotypes)_________________________ The Punnett square:
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IB Assessment Statement
Define sex linkage.
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IB Assessment Statement
Describe the inheritance of colour blindness and hemophilia as examples of sex linkage. Both colour blindness and hemophilia are produced by a recessive sex-linked allele on the X chromosome.
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Sex-Linked Traits Notes
__XX__= FEMALE ___XY__= MALE There are some traits and genetic disorders that are carried on the Sex Chromosomes (usually the X)___. There are many diseases are on the X chromosome Examples: Hemophilia Color blindness Genetic Disease are usually recessive.
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Genotype example __XN ___= normal gene
Examples: __XN ___= normal gene _ Xn _ = gene with trait or disorder
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IB Assessment Statement
State that a human female can be homozygous or heterozygous with respect to sex-linked genes. Explain that female carriers are heterozygous for X-linked recessive alleles.
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___XnY_____= male with trait ___XNY__= male without trait
MALES Because males only have 1 X chromosome if they inherit the X chromosome with the disease on it they have the disease because they only have one X chromosomes to hide the trait. Thus males inherit sex-linked genetic diseases more frequently than females. ___XnY_____= male with trait ___XNY__= male without trait
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Xn Xn _= female with trait XN Xn = female who is a carrier
FEMALES Inherit 2 X chromosomes_ Thus, females can also be a Carrier of the trait. This means even if a female does not have a disease, she can pass it to her offspring, if she is a carrier. Xn Xn _= female with trait XN Xn = female who is a carrier XN XN= female without trait
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Example problem: Colorblindness is a sex-linked trait. Cross a carrier female with a normal male. Select Symbols: Write the cross: Make a Punnet Square:
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IB Assessment Statement
Predict the genotypic and phenotypic ratios of offspring of monohybrid crosses involving any of the above patterns of inheritance PRACTICE PROBLEMS
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