Blood Group Notes

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

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.

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.

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

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:

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:

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:

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:

IB Assessment Statement Define sex linkage.

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.

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.

Genotype example __XN ___= normal gene Examples: __XN ___= normal gene _ Xn _ = gene with trait or disorder

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.

___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

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

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:

IB Assessment Statement Predict the genotypic and phenotypic ratios of offspring of monohybrid crosses involving any of the above patterns of inheritance PRACTICE PROBLEMS