Transcript Pedigree Diagrams - manorlakesscience

Dihybrid Cross
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Work through the example below:
Black hair is dominant, White hair is recessive
Short hair is dominant, Long hair is recessive
A homozygous dominant for both traits with a
homozygous recessive for both.
Show gametes, F1 genotypes, phenotypes and
ratios, then do the same for the F2 generation.
Pedigree Diagrams
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Aims:
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Must be able to recall the basics of
monohybrid and dihybrid crosses.
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Should be able to outline what a pedigree
diagram is and what it is used for.
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Could be able to draw and interpret different
pedigree diagrams.
Pedigree Diagrams
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Pedigree diagrams are used to show the inheritance
of a particular trait.
The diagram can be used to provide information
about the trait:
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Recessive or dominant
Located on autosomal or sex chromosome
Autosomal Dominant
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Idealised pattern:
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(Diagram p329)
Males and Females can be affected
All affected individuals have at least on affected parent
Transmission from either mother or father to either son or
daughter
Once a trait leaves a branch it will not return
In a large sample equal numbers of each sex affected
Examples include:
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Huntington’s Disease (HD gene), Familial Alzheimer’s (AD1
gene)
Autosomal Recessive
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Idealised pattern:
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(Diagram p330)
Males and Females can be affected
Two unaffected parents can have an affected child
All children of both affected parents MUST show the trait
The trait may disappear and reappear in a given branch
In a large sample equal numbers of each sex affected
Examples include:
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Cystic Fibrosis (CFTR gene), Thalassaemia (HBB gene)
X-Linked Dominant
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Idealised pattern:
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(Diagram p331)
Male with the trait passes it on to all daughters, no sons
Female with the trait may pass on to both daughters and
sons
Every affected person has at least one parent with the trait
If the trait disappears from a branch is does not reappear
Over a large number more affected females than males
Examples include:
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Incontinentia pigmenti (IP2 gene)
X-Linked Recessive
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Idealised pattern:
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(Diagram p331)
All sons of a female with the trait are affected
All daughters of a father with the trait will be carriers
All children of both parents with the trait will have the trait
None of the sons of a male with the trait and a female without
the trait will show the trait unless the female is a carrier
In a large sample more males than females show the trait
Examples include:
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ichthyosis (STS gene), Red-green colour blindness (CBD gene)
Activity
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Answer the questions from the sheet
provided.