Sex Determination, pedigrees and more

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Sex Determination, pedigrees and more
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I. Sex Determination in Humans

• General Information
• 1. 23 chromosomes come from Mom
• 2. 23 chromosomes come from Dad
• 3. 23rd pair of chrs. Is XX if ?
• 4. 23rd pair of chrs. Is XY if ?

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?Total of chrs. In normal human 46
I. Non-sex chrs. (autosomes)
2. Sex chrs.
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B. Details of Sex determination

• Having a Y chr. makes a ? child
• Absence of an X chr. Is fatal
• ?s make X Y sperm

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B. Details of Sex determination

• 4. If X sperm fertilizes egg, then ? child
• 5. If Y sperm fertilizes egg, then ? child
• ?Therefore, ? determines the sex of the child

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II. Pedigrees

• diagram showing the inheritance of a certain
  gene through several generations
• Symbols
• ?
• ?

breeding
breeding
offspring
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III. Sex-linked traits

• Usually found on X chromosome
• Affects males more than females
• Females can be carriers, not have the disorder
  (but can pass it to offspring)
• Examples color blindness and hemophilia

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IV. Hemophilia

• Background Facts
• 1. Bleeding disorder
• 2. Caused by lack of clotting factor
• 3. Slight injury or nose-bleed can be fatal

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IV. Hemophilia

• 4. Recessive sex-linked genetic disease
• 5. Info. on X chromosome (no info. On Y)

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II. History

• One of Victorias Secrets
• Queen Victoria of
• England
• was a carrier
• of hemophilia

Victoria, age 16
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II. History
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II. History
Queen Victorias Family 1881
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Queen Victorias descendants
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Alexei Romanov, son of Tsar Nicolas II
One of the most famous hemophiliacs was Russian
Prince Tsarevitch Alexei, killed along with all
his family during the Russian revolution in 1917.
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Treatment

• Transfusions w/ clotting factor VIII
• Danger
• HIV other
• blood-borne
• pathogens

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Hemophilia problem

• Alice is a carrier
• Her husband does not have the disorder.
• Can their children have the disorder?
• Yes!
• Lets use a Punnett square to determine the
  probabilities.
• X

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Hemophilia problem