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Transcript
Human Heredity: Karyotypes and Pedigrees Mrs. Kooiman LSHS 09-10 The people in your family have similar traits: Who do you look like? Your mom? Or do you take after your dad? Vocabulary karyotype sex chromosome autosome pedigree 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). Karyotype These human chromosomes have been cut out of a photograph and arranged to form a karyotype. There are 46 chromosomes in this karyotype of somatic cells There are 23 pairs of somatic cells The first 22 pairs are called autosomes The last pair are called sex chromosomes XX = Female XY = Male What is the gender of this karyotype? Males and females are born in a roughly 50 : 50 ratio because of the way in which sex chromosomes segregate during meiosis. All human egg cells carry a single X chromosome. However, half of all sperm cells carry an X chromosome and half carry aY chromosome. This ensures that just about half, 2 out of 4, of the zygotes will be XX This ensures that just about half, 2 out of 4, of the zygotes will be XY 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. A pedigree chart shows the relationships within a family A CIRCLE represents a Female, A SQUARE represents a Male, ■ A HORIZONTAL line represents a marriage A VERTICAL line and a BRACKET connect the parents to their children Generation 1 had 5 children How many sons? How many daughters? The children are listed from LEFT to RIGHT The OLDEST child is first The YOUNGEST child is last A SHADED circle or square means the person expresses the trait. An OPEN circle or square means the person does not express the trait.