Pedigree Charts What is a pedigree? Constructing a pedigree Interpreting a pedigree The family tree of genetics
What is a Pedigree Chart? Slide # 2 1. A Pedigree chart traces the inheritance of a particular trait through several generations. 2. One GOAL of using a pedigree chart is to figure out who arecarriers of the trait, because this information is typically unknown. a. Carrier: someone who is heterozygous for a trait.
Male Female Constructing a Pedigree Slide # 3
Constructing a Pedigree Slide # 4 1. Mated Pair: • Horizontal Line 2. Children: - Vertical line 3.More than one child: • a horizontal line is drawn with a vertical line coming down for each sibling.
Constructing a Pedigree Slide # 5 1. Fraternal twins- can be the same or different gender a. Two line branching from the same point b. two different eggs and two different sperm cells. 2. Identical twins-always same gender a. Also called maternal twins b. Same as fraternal twins but a horizontal line is added. c. One egg and one sperm unite and later split to create two babies
I II III Generations Slide # 6 1. Roman numerals to the left of the pedigree show the generations. 2.Birth Order: children are listed in birth order with oldest on left and youngest on the right.
1. Full Shaded: a. Affected person who shows a disorder 2. Half shaded: Autosomal carrier 3. Circle with dot: X-linked carrier –always female 4. Deceased Slide # 7 More Symbols in a Pedigree Chart
Predicting using Pedigree Charts Slide # 8 1. Pedigrees are used to find out: a. who are carriers of the disorder b. the probability of having a future child with the disorder. 2.To begin to interpret a pedigree, first determine if the disorder is: a. Autosomal dominant b. Autosomal recessive c. Sex-linked (carried on the Xchromosome)
Interpreting a Pedigree Chart Slide # 9 First ask: Is it a Sex-linked or Autosomal Disorder? 1. If there is a much larger number of males than females who are affected then the disorder is Sex-linked. 2. If there is a 50/50 ratio between males and females who are affected then the disorder is autosomal.
Interpreting a Pedigree Chart Slide # 10 1. If it is autosomal disorder then ask: Is it dominant or recessive? 2. If two parents do not show the trait and their children do show it, then it is an autosomal recessive disorder - (parents are carriers or heterozygous) 3. If the disorder is autosomaldominant, then at least one of the parents must show the disorder.
Note: Slide # 11 1. The following pedigree charts show affected individuals only. 2. Carriers are unknown at this point.
Practice Examples Slide # 12 Does this pedigree show a Sex-linked or Autosomal disorder? Answer: Sex-Linked disorder much larger number of males are affected
Practice Examples Slide # 13 Does this pedigree show a Sex-linked or Autosomal disorder? Answer: Autosomal disorder 50/50ratio between males and females
Practice Examples Slide # 14 Does this pedigree show a Autosomal Dominant or Recessive disorder? Answer: Autosomal dominant disorder At least one parent of the affected children show the disorder
Practice Examples Slide # 15 Does this pedigree show a Sex-linked or Autosomal disorder? Answer: Autosomal disorder 50/50 ratio between males and females
Practice Examples Slide # 16 Does this pedigree show a Autosomal Dominant or Recessive disorder? Answer: Autosomal recessive disorder Two parents do not show the trait but their children do show it (heterozygous parents)
Dd Dd Dd Dd dd dd dd dd dd dd Autosomal Recessive Genotypes and Carrier determination D = Normal hearing d = deafness Slide # 17 Dd D? Dd