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Heredity Review of Traits A trait is a characteristic of something Inherited Traits All can be both behavioral or physical traits are coded in the DNA of the organism organisms contain DNA, so all organisms pass on traits Examples of inherited traits hitchhiker Is thumb this a physical trait or a behavioral trait? Examples of inherited traits widow’s hairline Is peak this an inherited trait or an acquired trait? Examples of inherited traits attached How earlobes many people in the class have this inherited trait? Examples of inherited traits tongue Is rolling this a physical trait or a behavioral trait? Examples of inherited traits hand Is clasping this a physical trait or a behavioral trait? What determines traits? Traits are written on chromosomes Chromosomes come in pairs One chromosome comes from mom One chromosome comes from dad What determines traits? Is this a plant or animal cell? What evidence suggests your inference? Each particular section of a chromosome codes for a gene Humans have about 25,000 genes – we are still discovering! What determines traits? Each gene codes for a protein that will help determine a trait The different versions of a trait are called alleles. For instance, the same spot on matching chromosomes could contain an allele for straight thumb or an allele for hitchhiker thumb. What determines traits? Alleles are kinda like different stitching on the pockets of different brands of jeans They perform the same function, but are slightly different Allele for “w” Allele for “flying bird” What determines traits? Your unique alleles determine your many unique traits No two humans could be identical, because there are almost an infinite number of gene combinations How do we read the code? The genotype is the code written on the DNA The phenotype is the resulting appearance (pheno is like photo) How do 2 alleles make 1 trait? Dominant alleles are like class clowns – you always know if they are in the room. Recessive alleles are like shy people – you don’t know they are there unless they are alone How do 2 alleles make 1 trait? If a dominant allele is present in the genotype, that allele’s phenotype will show outwardly. Example, Straight Thumb is dominant over hitchhiker’s Thumb H h How do 2 alleles make 1 trait? The only way a hitchhiker’s thumb shows up in the phenotype is if 2 recessive traits are inherited in the genotype. H+H= H+h= h+h=
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