Chapter 5: 5.6 Intro to Pedigree Analysis Flashcards
Define:
Pedigree chart
A series of symbols used to depict family members affected by a genetic trait in a family tree
In a pedigree chart:
What do circles and squares represent?
- Circles represent females
- Squares represent males
In a pedigree chart:
What do coloured shapes represent?
Individuals affected by a genetic trait (e.g. color blindness)
In a pedigree chart:
What do roman numerals represent?
Stands for the generation the individuals belong to
In a pedigree chart:
What do the digits represent?
Identifies the individual in each generation
Define:
Founding parents
The male and female in the first generation
Define:
Founding family
Consists of the founding parents and their children
What can pedigree charts be used for?
- Studying the genetics of inherited diseases
- Determine the mode of transmission
Define:
Dominance
Whether a disease is dominant or recessive
Define:
Linkage
Whether a disease is X-linked (on the X chromosome) or autosomal (not on sex chromosomes)
What are the 4 key things to remember when analyzing pedigrees?
- An unaffected person cannot carry any alleles of a dominant trait
- An unaffected person can be carrying the trait if it is recessive
- If the trait is X-linked, a recessive allele is sufficient to affect a male
- Fathers transmit X-linked genes to their daughters only, while mothers transmit X-linked genes to both their sons and daughters
Why must an unaffected person not carry any alleles of a dominant trait?
Having the allele would mean the trait would present (hence, be affected)
Why can an unaffected person be carrying the trait if it is recessive?
Recessive traits requires two alleles in order to show disease
Why do fathers only transmit X-linked genes to their daughters only?
Males only have on X chromosome
* If they have a son, they must give their Y chromosome for it to be a son
