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Download Pedigrees and Karyotypes What is a pedigree? How do you read a
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Transcript
11/4/2014 What is a pedigree? Pedigrees and Karyotypes Date: __________________ • Chart showing the inheritance pattern of a trait, disease, or disorder, through multiple generations in the same family. • The genotype and the phenotype of the family members and the inheritance pattern of a trait can be tracked. – A trait can be… • Autosomal dominant or autosomal recessive • Sex-linked dominant or sex-linked recessive How do you read a pedigree? Male Female Carrier male Carrier female Affected male Affected female Marriage line (breeding) A Real Pedigree: • Is it autosomal or sex-linked? • Is it dominant or recessive? Children • A trait is DOMINANT if it appears EVERY generation, and RECESSIVE if it skips a generation. • A trait is AUTOSOMAL if it affects both sexes about equally, SEX-LINKED if it affects mostly males. • Is it autosomal or sex-linked? • Is it dominant or recessive? What is a karyotype? • A picture of all of the chromosomes in a cell. • Where can I get one? – Genetic counseling centers. • How do they do it? – They use a chemical to stop the cell cycle during metaphase, and extract the genetic material from the cell. They stain it, and arrange the chromosomes by size. 1 11/4/2014 Why should people get karyotypes? • They can show large-scale chromosomal abnormalities, like deletions or extra copies of chromosomes. • Downside – only shows large changes, and small mutations (like sickle-cell anemia, colorblindness, or progeria) will not show up. Expressing Karyotypes • Normal karyotypes are expressed as follows: – Females: 46,XX – Males: 46,XY • Can you figure out how we’ve expressed these? Chromosomal Disorders • Usually arise from a nondisjunction during meiosis. – Nondisjunction: incorrect separation of chromosomes; leads to too many copies of a chromosome or not enough. – Remember: there should be TWO of every chromosome! • Includes trisomy and monosomy – Trisomy: three copies of a chromosome – Monosomy: one copy of a chromosome Expressing Common Chromosomal Disorders • Down Syndrome: 47,XX(+21) or 47,XY(+21) (1 in 800 births) • Cri-du-chat Syndrome: 46,XX(del5) or 46,XY(del5) (1 in 50,000 births) • Turner Syndrome: 45,XO • Klinefelter Syndrome: 47,XXY • Edward Syndrome: 47,XX(+18) or 47,XY(+18) (1 in 8,000 births) • Patau Syndrome: 47,XX(+13) or 47,XY(+13) (1 in 20,000 births) • XXX syndrome: 47,XXX (1 in 1200 births) • XYY syndrome: 47,XYY 2