Human Heredity: Karyotypes and Pedigrees

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Human HeredityKaryotypes and Pedigrees

• Mrs. Kooiman
• LSHS
• 09-10

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The people in your family have similar traits
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Who do you look like? Your mom?
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Or do you take after your dad?
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Vocabulary

• karyotype
• sex chromosome
• autosome
• pedigree

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Human Chromosomes

• By taking a look at the nucleus, we will see
  chromosomes of a human cell.
• To analyze chromosomes, cell biologists
  photograph cells in mitosis, when the chromosomes
  are fully condensed and easy to see.
• The biologists then cut out the chromosomes from
  the photographs and group them together in pairs.
  
• A picture of chromosomes arranged in this way is
  known as a karyotype (KAR-ee-uh-typ).

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Karyotype 

• These human chromosomes have been cut out of a
  photograph and arranged to form a karyotype.

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• There are 46 chromosomes in this karyotype of
  somatic cells
• There are 23 pairs of somatic cells
• The first 22 pairs are called autosomes

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• The last pair are called sex chromosomes
• XX Female
• XY Male
• What is the gender of this karyotype?

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• Males and females are born in a roughly 50 50
  ratio because of the way in which sex chromosomes
  segregate during meiosis.  

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• All human egg cells carry a single X chromosome.

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• However, half of all sperm cells carry an X
  chromosome and half carry a Y chromosome.

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• This ensures that just about half, 2 out of 4, of
  the zygotes will be XX

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• This ensures that just about half, 2 out of 4, of
  the zygotes will be XY

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Pedigree Charts

• Human genes are inherited according to the same
  principles that Gregor Mendel discovered in his
  work with garden peas.
• However, in order to apply Mendelian genetics to
  humans, biologists must identify an inherited
  trait controlled by a single gene to ensure that
  the trait is actually inherited and not the
  result of environmental influences.

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• A pedigree chart shows the relationships within a
  family

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• A CIRCLE represents a Female, ?
• A SQUARE represents a Male,
• A HORIZONTAL line represents a marriage

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• A VERTICAL line and a BRACKET connect the parents
  to their children
• Generation 1 had 5 children
• How many sons?
• How many daughters?

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• The children are listed from LEFT to RIGHT
• The OLDEST child is first
• The YOUNGEST child is last

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• A SHADED circle or square means the person
  expresses the trait.
• An OPEN circle or square means the person does
  not express the trait.