If a woman is a carrier of an X-linked recessive allele for a disorder and her mate does not, their sons have a ______ chance of inheritingthe disorder.  ______ of their daughters will have it, but ______ of them are likely to be carriers.

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If a man has an X-linked recessive disorder and his mate does not carry the allele for it, _____ of their girls will be carriers. _____ of their boys will inherit the harmful allele. 

• Why are there more X sex linked traits?Why are there more X sex linked traits?

• Linked genes are usually …Linked genes are usually …

• Mutations in an organisms gametes = ?Mutations in an organisms gametes = ?

• Mutations that cause death = ? Example from class = ?Mutations that cause death = ? Example from class = ?

• What type of mutation causes Down syndrome (2 correct answers)?What type of mutation causes Down syndrome (2 correct answers)?

Read 12.2 and answer #s 1-8 on the bottom of page 248 – DUE tomorrow (Friday 5-13)

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PedigreePedigree – diagram that – diagram that shows how a shows how a trait is trait is inherited inherited over several over several generationsgenerations

Squares = ?

Circles = ?

• Study the simple Study the simple pedigree. The man is pedigree. The man is red (pink) because…?red (pink) because…?

• The daughters are The daughters are blue because …?blue because …?

• Is it possible to get a Is it possible to get a son that has son that has Hemophilia or is a Hemophilia or is a carrier? Explain!carrier? Explain!

• If one of the sons If one of the sons hooks up with a hooks up with a female carrier, what female carrier, what will happen?will happen?

Hemophilia (X-linked recessive) Pedigree from Queen Victoria

How did she become a carrier? 1. __________________________

________________

2._____________________________________ ___________

3.__________________________________________

X-Linked TraitsX-Linked Traits• Traits carried on the Traits carried on the X chromosomeX chromosome

– Who will show more X-linked disorders, males or Who will show more X-linked disorders, males or females? Why?females? Why?• Males – b/c they only have one X (XY) so it Males – b/c they only have one X (XY) so it

doesn’t matter if trait is dominant or recessivedoesn’t matter if trait is dominant or recessive– ExamplesExamples::

• ColorblindnessColorblindness – carried on – carried on X-chromosomeX-chromosome

• HemophiliaHemophilia – impaired blood – impaired blood clottingclotting

• CarriersCarriers – – people who people who carry an allele for a carry an allele for a disorderdisorder, but do not have the disorder , but do not have the disorder (Heterozygous)(Heterozygous)

• Genetic disordersGenetic disorders – – any disease / disorder that any disease / disorder that has a genetic basishas a genetic basis

• PolygenicPolygenic – – characteristics that are influenced by characteristics that are influenced by several genesseveral genes– ExamplesExamples::

• Skin color – Skin color – six genessix genes• Other examples – Other examples – eye color, height, hair coloreye color, height, hair color

• Complex charactersComplex characters - - characteristics characteristics that are that are influenced strongly by influenced strongly by both environment and genesboth environment and genes

• Sun = Sun = darker skindarker skin

• Height = several genes but also Height = several genes but also nutrition and diseasenutrition and disease

An example of a human trait that is polygenic and a complex character = _____ because...

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• Who will show more X-linked disorders, males or females? Why?Who will show more X-linked disorders, males or females? Why?

• Linked genes are usually …Linked genes are usually …

• Germ-cell mutations = ?Germ-cell mutations = ?

• Chromosomal mutations cause changes to chromosome ___ or ___. Example from class = ?Chromosomal mutations cause changes to chromosome ___ or ___. Example from class = ?

• What is a pedigree?What is a pedigree?

• Multiple AllelesMultiple Alleles – genes that have – genes that have three three or more allelesor more alleles (usually 2) (usually 2)– ExampleExample: Blood Type : Blood Type – What are the blood types?What are the blood types?

• ABOABO– Three alleles – Three alleles – IIAA, I, IBB, i, i

• Blood TypesBlood Types – – A, B, AB, OA, B, AB, O

• Antigens – proteins, carbs etc on outside of red blood cells• Antibodies – immuno proteins that destroy unrecognized

antigens

• http://nobelprize.org/educational_games/medicine/landsteiner/

• “Blood typing activity” google – first link

How do you identify a dominant genetic disorder on a pedigree?

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Quizish Questish type deal on Friday 5-20. Also bring your binder last binder check likely.

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• CodominanceCodominance – when – when both alleles are both alleles are expressed in the phenotypeexpressed in the phenotype (I (IAA, I, IBB – – neither is dominant over the other – both neither is dominant over the other – both carbs are produced on cell surface)carbs are produced on cell surface)

• In codominance, In codominance, you see both traitsyou see both traitsRed cow x white cow = roan cowRed cow x white cow = roan cow

CodominanceCodominance

• Incomplete dominanceIncomplete dominance – – mix between two mix between two parentsparents (blend) (blend)

• In incomplete dominance, you see a In incomplete dominance, you see a mix or mix or blendblend of both traits of both traits

• ExampleExample::– straight hair mom X curly hair dad = straight hair mom X curly hair dad = wavywavy

haired childhaired child– Red flower x white flower = Red flower x white flower = pink pink flowerflower

Incomplete Dominance

X-Linked Traits (review)X-Linked Traits (review)• Traits carried on the X chromosomeTraits carried on the X chromosome

– Who will show more X-linked disorders, males or Who will show more X-linked disorders, males or females? Why?females? Why?• Males – b/c they only have one X (XY) (doesn’t Males – b/c they only have one X (XY) (doesn’t

matter if trait is dominant or recessive)matter if trait is dominant or recessive)– ExamplesExamples::

• Colorblindness Colorblindness • HemophiliaHemophilia

X-linked Dominant

• If mother affected equal chance of sons / daughters affected

• If father affected All daughters will have, sons ok

• No carriers possible

X-Linked Recessive• If mother carrier

50% chance son will be affected, no daughters will have (females can be carriers)

• If father affected Sons will be ok, All daughters are carriers

Autosomal Dominant

• Affected individual 50 / 50 chance of producing affected children

• No carriers possible

Autosomal Recessive

• Occurs if both parents are carriers (only 25% of the time)

• Carriers possible

• Single-Allele TraitsSingle-Allele Traits – – traits caused by one traits caused by one dominant alleledominant allele

• Huntington’s DiseaseHuntington’s Disease – –

– caused by one dominant allele. Onset is 30-40 so caused by one dominant allele. Onset is 30-40 so parents have children before they realize they parents have children before they realize they have ithave it

– Forgetfulness, irritability, muscle spasms and Forgetfulness, irritability, muscle spasms and mental illness, then deathmental illness, then death

– Genetic testingGenetic testing now beginning to be used to now beginning to be used to determine if either parent has diseasedetermine if either parent has disease