Understand how to use pedigrees to determine and explain the inheritance of traits

1) How to use pedigrees:

They are diagrams in which people are represented by symbols. Circles represent female and squares represent males.
The bottom line represents the offspring of the couple above it.

Dark symbols are used to indicate someone who is affected with a genetic condition.
Not colored symbols indicate someone who is NOT affected. 
A heterozygote carrier.can be represented as grey color.

2) How traits are inherited:
Humans have 23 pairs of chromosomes (46 chromosomes)  because 23 chromosomes are inherited from the father and the other 23 come from the mother.

With 23 sets, you have two copies of each gene. This copies can be different or the same and based on that there could be different traits for the same gene like black, brown or blond hair.

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