Transcript Pedigrees
Pedigrees Essential Questions: What is a Pedigree? What do they show? What are the parts of a pedigree? How do you interpret a pedigree? How do you make a pedigree? What is a Pedigree? • Pedigrees study how a trait is passed from one generation to the next. (A family Tree) – By placing the oldest generations on top by birth order – By recording births and deaths – By recording phenotypes of family members • Infers genotypes of family members • Remember, Conditions and Disorders can be carried on… – Autosomes (22 pairs of chromosomes) – Sex Chromosomes (X or Y) – Number of Chromosomes (called N: either N > 46 > N) • Keep in mind: traits are influenced heavily by non-genetic factors or environmental factors… – – – – Life Style and Geography Nutrition and Exercise Toxins (mutagens) Disease and Age Parts of a Pedigree • Shapes: – Squares are males (XY) – Circles are females (XX) • Lines: – Horizontal lines connect breeding couples – Vertical lines connect parents to children – A diagonal line means death. • Filling: – Shading means the individual has the trait – Half shading or a dot means they carry the gene called a “carrier” – No shading means the individual does not have the trait • Identifying Individuals: – Roman numerals show generations – Numbers assign an individual to a generation and birth order • • Example: What happened to II, 1? What’s fishy about individual III, 5? More Pedigree Symbols & Meanings Interpreting Pedigrees 1. Determine if the trait is dominant or recessive. – Every other generation: It is recessive – Every generation: It is Dominant • 2. Determine if the trait is autosomal or sex linked. – Affects males and females equally: Autosomal (Aa) – Affects one sex more than the other, especially males: Sex-linked (XCXc or XcY) • Typically sex-linked disorders or traits are carried on the X chromosome – Females tend to “carry” a trait and affect their sons. – Females get the trait from an affected father or carrier/affected mother. – Affected males got it from their mother and give it to their daughters to “carry.” Interpreting Pedigrees Review: Sex-Related Punnett Squares • The genes for these traits are on the X chromosome, because boys only receive one X chromosome they are more likely to inherit disorders passed to them from their mother who would be a carrier. – Humans have 22 pairs of autosomes and 1 pair of sex chromosomes. – Males are XY • Males donate their Y chromosome to their sons only and their X chromosome to their daughters. • They determine the sex of the child! – Females are XX • Females donate one or the other of their X chromosomes to their sons and daughters. • Many times in women the other X chromosome coils up and deactivates to become a Barr body. • Hemophilia and Colorblindness are examples of sex linked traits, the punnett square shows how a woman who is a carrier passes the trait to her son, but not her daughters. – In what only case could you have a daughter with hemophilia and/or colorblindness? – She inherits a recessive from her mother and her father! How to interpret a pedigree: 1. Determine if it is dominant or recessive. 2. Determine if it is autosomal or sex-linked. 3. Assign genotypes to affected (shaded) individuals first. – If Autosomal then use two alleles to show inheritance. (AA, Aa or aa for example) – If Sex-linked then use one allele for males, two for females: • The shaded males will carry the gene (XcY) and be affected. • The females can be affected (XcXc) if they inherited two copies of the gene 4. Assign remaining genotypes to unaffected (unshaded) individuals. – If Sex-Linked: the unshaded males will not carry the gene (XCY) and not be affected), carriers marked with a dot(XCXc), along with unshaded unaffected females (XCXC) 5. Double check your work, does the pedigree make sense? Your Turn! Is this dominant or recessive? Is this Autosomal or Sex-linked? Assign genotypes to the pedigree to show the inheritance pattern. Check your work Type of Inheritance? Autosomal dominant inheritance. Your turn! Is this dominant or recessive? Is this Autosomal or Sex-linked? Assign genotypes to the pedigree to show the inheritance pattern. Check your work. Type of Inheritance? Sex linked Recessive How to construct a Family Pedigree Part I: Start with you! How to construct a Family Pedigree Part II: Siblings How to construct a Family Pedigree Part III: Parents How to construct a Family Pedigree Part IV: Extended Family Members (Aunts, Uncles, Cousins, Nieces & Nephews) How to construct a Family Pedigree Part V: Grandparents How to construct a Family Pedigree Part VI: Add information! How to construct a Family Pedigree Part VII: Double Check! • Double check your work. Does your family tree make sense? • This is useful to your doctor and researching family histories.