Heredity

1. Heredity

2. Review of Traits • A trait is a characteristic of something • Traits can be both behavioralor physical • Inherited traits are coded in the DNA of the organism • All organisms contain DNA, so all organisms pass on traits

3. Examples of inherited traits • hitchhiker thumb • Is this a physical trait or a behavioral trait?

4. Examples of inherited traits • widow’s peak hairline • Is this an inherited trait or an acquired trait?

5. Examples of inherited traits • attached earlobes • How many people in the class have this inherited trait?

6. Examples of inherited traits • tongue rolling • Is this a physical trait or a behavioral trait?

7. Examples of inherited traits • hand clasping • Is this a physical trait or a behavioral trait?

8. What determines traits? • Traits are written on chromosomes • Chromosomes come in pairs • One chromosome comes from mom • One chromosome comes from dad

9. 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!

10. 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.

11. 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”

12. 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

13. 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)

14. 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

15. 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

16. 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 =