Presentation on theme: "Pedigrees A pedigree is a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. In a pedigree,"— Presentation transcript:
1 PedigreesA pedigree is a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships.In a pedigree, squares show males and circles show females. Horizontal lines connecting a male and female show mating. Vertical lines extending down from a couple show their children. Subsequent generations are written underneath the parental generations.it is customary to shade in the symbol of all individuals that possess the trait of interest.
2 Royal family pedigree expressing the hemophilia allele
3 My pedigree shows that: The allele for Huntington’s Disease is:Sex linked on the YSex linked on the XAutosomal dominant (caused by a dominant allele)Autosomal recessive (caused by a recessive allele)
4 Sex-linked traits22 of your 23 pairs of homologous chromosomes act the same regardless of your sex- autosomal.The 23rd pair are sex chromosomesFemales are XX (inherit an X from each parent)Males are XY (inherit X from mom and Y from dad).Genes found on either the X or Y chromosomes are called sex-linked.
5 Sex-linked cont.There are over a 1,000 X-linked traits; Y-linked traits are rare and mostly deal with sperm production.In woman, a recessive allele on one X can be masked by a dominant allele on the other X.In men, recessive alleles on the X are always expressed since there is not a corresponding allele on the Y.This explains why woman are usually carriers of X-linked traits, but rarely express them.For more info:
6 Autosomal Dominant For those traits exhibiting dominant gene action: affected individuals have at least one affected parentthe phenotype generally appears every generationtwo unaffected parents only have unaffected offspringThe following is the pedigree of a trait controlled by dominant gene action.
7 Autosomal Recessive For those traits exhibiting recessive gene action: unaffected parents can have affected offspringaffected progeny are both male and femaleThe following is the pedigree of a trait controlled by recessive gene action.