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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– Dominant over blood group O
• 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
– 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.
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
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