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Pedigree Charts Pedigree Charts The family tree of The family tree of genetics genetics

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The family tree of genetics. Pedigree Charts. Overview. What is a pedigree? Definition Uses Constructing a pedigree Symbols Connecting the symbols Interpreting a pedigree. What is a Pedigree?. A pedigree is a chart of the genetic history of family over several generations. - PowerPoint PPT Presentation

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Page 1: Pedigree Charts

Pedigree ChartsPedigree Charts

The family tree of geneticsThe family tree of genetics

Page 2: Pedigree Charts

OverviewOverview

I.I. What is a pedigree? What is a pedigree? a.a. DefinitionDefinition

b.b. UsesUses

II.II. Constructing a pedigree Constructing a pedigree a.a. SymbolsSymbols

III.III. Connecting the symbolsConnecting the symbols

IV.IV. Interpreting a pedigree Interpreting a pedigree

Page 3: Pedigree Charts

What is a Pedigree?What is a Pedigree?

A pedigree is a chart of the genetic history A pedigree is a chart of the genetic history of family over several generations.of family over several generations.

Scientists or a genetic counselor would find Scientists or a genetic counselor would find out about your family history and make this out about your family history and make this chart to analyze.chart to analyze.

Page 4: Pedigree Charts

Constructing a PedigreeConstructing a Pedigree

MaleMale

FemaleFemale

Page 5: Pedigree Charts

Connecting Pedigree SymbolsConnecting Pedigree Symbols

Fraternal twinsFraternal twins

Identical twinsIdentical twins

Examples of connected symbols:Examples of connected symbols:

Page 6: Pedigree Charts

Connecting Pedigree SymbolsConnecting Pedigree Symbols

Married CoupleMarried Couple

SiblingsSiblings

Examples of connected symbols:Examples of connected symbols:

Page 7: Pedigree Charts

ExampleExample

What does a pedigree chart look like?What does a pedigree chart look like?

Page 8: Pedigree Charts

Symbols in a Pedigree ChartSymbols in a Pedigree Chart

Affected Affected X-linkedX-linked Autosomal carrierAutosomal carrier DeceasedDeceased

Page 9: Pedigree Charts

Interpreting a Pedigree ChartInterpreting a Pedigree Chart

1.1. Determine if the pedigree chart shows an Determine if the pedigree chart shows an autosomal or X-linked disease.autosomal or X-linked disease.

– If most of the males in the pedigree are If most of the males in the pedigree are affected the disorder is X-linked affected the disorder is X-linked

– If it is a 50/50 ratio between men and If it is a 50/50 ratio between men and women the disorder is autosomal.women the disorder is autosomal.

Page 10: Pedigree Charts

Example of Pedigree ChartsExample of Pedigree Charts

Is it Autosomal or X-linked?Is it Autosomal or X-linked?

Page 11: Pedigree Charts

AnswerAnswer

AutosomalAutosomal

Page 12: Pedigree Charts

Interpreting a Pedigree ChartInterpreting a Pedigree Chart

1.1. Determine whether the disorder is Determine whether the disorder is dominant or recessive.dominant or recessive.

– If the disorder is dominant, one of the If the disorder is dominant, one of the parents must have the disorder.parents must have the disorder.

– If the disorder is recessive, neither If the disorder is recessive, neither parent has to have the disorder because parent has to have the disorder because they can be heterozygous.they can be heterozygous.

Page 13: Pedigree Charts

Example of Pedigree ChartsExample of Pedigree Charts

Dominant or Recessive?Dominant or Recessive?

Page 14: Pedigree Charts

AnswerAnswer

DominantDominant

Page 15: Pedigree Charts

Example of Pedigree ChartsExample of Pedigree Charts

Dominant or Recessive?Dominant or Recessive?

Page 16: Pedigree Charts

AnswerAnswer

RecessiveRecessive

Page 17: Pedigree Charts

Historic PedigreesHistoric Pedigrees

Queen Victoria- Hemophilia sex linked blood Queen Victoria- Hemophilia sex linked blood disorder( bleeder)disorder( bleeder)

Page 18: Pedigree Charts

Hemophilia is a hereditary (X-linked, recessive) Hemophilia is a hereditary (X-linked, recessive) blood disorder that affects the proper clotting of blood disorder that affects the proper clotting of blood. It is a disease that affects males much more blood. It is a disease that affects males much more frequently (1 in 10,000) than females (1 in frequently (1 in 10,000) than females (1 in 100,000,000). This occurs because a critical blood-100,000,000). This occurs because a critical blood-clotting gene is carried on the clotting gene is carried on the X chromosomeX chromosome. So . So because males carry only one X chromosome, if it is because males carry only one X chromosome, if it is defective he will have hemophilia. Females, on the defective he will have hemophilia. Females, on the other hand, carry two other hand, carry two X chromosomesX chromosomes. If only one is . If only one is defective, the other normal defective, the other normal X chromosomeX chromosome can can compensate. The woman will have normal blood compensate. The woman will have normal blood clotting, but she will still be a clotting, but she will still be a carriercarrier of the recessive of the recessive defective gene. A woman will know if she is a defective gene. A woman will know if she is a carriercarrier sooner through genetic testing or later if any of her sooner through genetic testing or later if any of her children are hemophiliacs. Naturally, female children are hemophiliacs. Naturally, female hemophiliacs are rare because it takes two hemophiliacs are rare because it takes two defective X defective X chromosomeschromosomes in order for the condition in order for the condition to occur. Women with the recessive to occur. Women with the recessive genegene that that codes for hemophilia simply pass it on to their codes for hemophilia simply pass it on to their offspring.offspring.

Page 19: Pedigree Charts

Royal DiseaseRoyal Disease

Hemophilia has often been referred to as The Hemophilia has often been referred to as The Royal DiseaseRoyal Disease. The marriage of England's Queen . The marriage of England's Queen Victoria and Prince Albert marked the beginning of Victoria and Prince Albert marked the beginning of hemophilia in the British royal line. Queen Victoria, hemophilia in the British royal line. Queen Victoria, Queen of England from 1837 to 1901, was a Queen of England from 1837 to 1901, was a carrier of the carrier of the hemophilia genehemophilia gene. She had nine . She had nine children and as English royal family members children and as English royal family members married into royalty of other countries, the disease married into royalty of other countries, the disease eventually infected most of the royal houses of eventually infected most of the royal houses of Europe. So hemophilia gained its title of The Royal Europe. So hemophilia gained its title of The Royal Disease because it spread through the royal Disease because it spread through the royal families of Europe through Victoria's descendants. families of Europe through Victoria's descendants.

Page 20: Pedigree Charts
Page 21: Pedigree Charts
Page 22: Pedigree Charts

Queen Victoria's eighth child, Leopold, was Queen Victoria's eighth child, Leopold, was her only hemophiliac child. Two of Queen her only hemophiliac child. Two of Queen Victoria's daughters, Beatrice and Alice, Victoria's daughters, Beatrice and Alice, were also carriers of hemophilia. The were also carriers of hemophilia. The daughter's were the links that passed the daughter's were the links that passed the disease onto the Spanish, German and disease onto the Spanish, German and Russian royal families. Russian royal families.

Page 23: Pedigree Charts
Page 24: Pedigree Charts

SummarySummary

Pedigrees are family trees that explain your Pedigrees are family trees that explain your genetic history.genetic history.

Pedigrees are used to find out the Pedigrees are used to find out the probability of a child having a disorder in a probability of a child having a disorder in a particular family.particular family.

To begin to interpret a pedigree, determine if To begin to interpret a pedigree, determine if the disease or condition is autosomal or X-the disease or condition is autosomal or X-linked and dominant or recessive.linked and dominant or recessive.