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Pedigree charts helping scientists trace the passing on of traits pedigree charts our story begins with a couple we've got a brown haired male and a blond-haired female these two people met fell in love and got married once married our couple decided to reproduce in their family they had two children their firstborn was a blond-haired son and their second form was a brown haired female later in her life our brown haired female met a brown haired male they too fell in love decided to get married and reproduced in their family they had two children their firstborn was a blond-haired female and their second born was a brown haired female scientists look at this family tree and simplify it instead of using faces and names scientists use symbols squares represent males in circles represent females this is an example of a pedigree chart scientists will then use this information to track the passing on of traits in our family we'll look at the passing on of the blond-haired trait here's our family tree next to a pedigree together we can work to fill this out the trait that we're looking at is the trait of brown hair brown hair is dominant to blonde hair in our example our male is heterozygous his genes or hair color our baby little be in the pedigree chart we will shade in his shape half way this will show us that he's carrying the recessive trait for blind hair the wife and our example has blonde hair her genes are two lowercase bees on the pedigree chart to the right we will shade her shape in completely her firstborn had blonde hair so his shape will be shaded in completely the son-in-law was heterozygous or he's carrying the recessive gene we will shade his shape in half way the daughter is also a heterozygous carrier we will shade her circle in half way their firstborn had blonde hair so to represent this in the pedigree chart we will shade her circle incompletely and her sister inherited two dominant genes for hair color we will leave her shape on shaded if we take a look at the pedigree we can review what we learned squares represent boys circles represent girl a half shaded in shape represents a carrier a carrier is someone who has one dominant and one recessive gene for specific trait if the shape is fully shaded in we say that the person is showing the recessive trait in our example the recessive boy would have blonde hair and so what a recessive girl and their genes would be - or a case B's so the next time you look at a family tree think like a scientist and try and pick a trait and trace it pedigree charts tracing or passing on of human traits