Download Pedigree Charts

Pedigree Charts
Pedigrees
Breeding experiments are not ethical, or even possible, with humans, as they are with plants and animals. As a result, pedigree charts provide one of the few ethical ways of studying human genetics. • Pedigrees are very similar to family trees, except pedigrees study a specific trait within a family. • A pedigree is a way to analyze how a trait "runs in the family".
Conventions for using Pedigrees
Males are represented by a square.
Females are represented by circle. Shaded symbols represent a person that expresses the studied trait. A pedigree chart is a type of flowchart that uses symbols to show the inheritance patterns of traits in a family over many generations. They can be used to study the transmission of a disease or hereditary condition in a family.
(Mating)
Offspring (Siblings)
Conventions for using Pedigrees ­ continued
• Every generation (row) is represented by a Roman numeral, • Each member in a generation is represented by an Arabic numeral.
(Arabic numerals numbered from the left.) Conventions for using Pedigrees ­ continued
• In the pedigree chart, individuals are placed in a generation (a row) from oldest to youngest (left to right).
For example, the affected individuals in the pedigree below are:
II3, IV2 and IV3.
• Pedigrees are often used to determine the mode of inheritance ‐ dominant or recessive or sex‐linked ‐ of a genetic diseases/disorder. Pedigrees
• Autosomal Inheritance ‐ the inheritance of traits whose genes are found on the autosomes (chromosomes 1 to 22 in humans)
• Inherited genetic disorders caused by autosomal genes are classified as either autosomal dominant or autosomal recessive.
• An autosomal dominant disorder occurs when the disease‐causing allele is dominant and an affected individual has one or both copies of the allele.
• An autosomal recessive disorder occurs when the disease‐causing allele is recessive and an affected individual has both copies of the allele.
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Pedigree Charts
Consider this pedigree for the dominant trait of tongue‐rolling.
The pedigree chart below shows inheritance of the gene that causes albinism. A and B represent a couple who had five children, including C and E. Only one of the children, E, had albinism. “E” and her husband had five children, including G. In the pedigree below write the genotypes of the individuals who are labeled with letters, using A to represent the dominant allele and a to represent the recessive allele. HINT: Start by indicating the genotypes of E and F. a) Determine if this is a dominant or recessive trait and explain why. b) Label the genotypes of the individuals who's genotype that you know for certain.
A. State the relationship of each of the following to individual II‐3: I ‐ 2 ______________
II‐2 ______________
II ‐ 5 ______________ III‐2 ______________
III ‐ 3 ______________
B. State the genotype of the following individuals:
III‐3 ______________
I ‐ 2 ______________ III‐4 ______________
II‐1 ______________ III ‐ 2 ______________ Analyze the pedigree below to determine the mode of inheritance. Is the pedigree below for a trait that has an autosomal recessive mode of inheritance, an autosomal dominant , or X‐linked recessive mode of inheritance. Explain why??
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