Heredity : the passing of traits from parent to offspring

1. Heredity : the passing of traits from parent to offspring Traits are controlled by genes, SO what is GENETICS? Genetics: The study of how traits are inherited.

2. GREGOR MENDEL • First known geneticist and “father of genetics” • Was an Austrian monk and was born in 1822 • Did most of his genetic studies on pea plants

3. WHAT ARE ALLELES? • Are ONE FORM of a gene (there can be more than one form) • Sex cells have one form of a gene on their chromosomes • Body cells have two forms or ALLELES for a single gene (you got one from Mom and one from Dad) • One may be dominant over another. If this happens, the dominant gene is the one expressed. If not, the recessive trait is expressed.

4. DOMINANT AND RECESSIVE • A Dominant trait: will always be expressed and will “mask” a recessive trait • A recessive trait can only be expressed if there are nodominant alleles present.

5. Example: Eyecolor—Brown color is dominant and blue is recessive. A person can have a brown allele and a blue allele but still have brown eyes because the brown allele is dominant and “hides” the blue allele.

6. Example:R= dominant r = recessive • Generally, dominant alleles are represented with a capital letter, and recessive alleles are represented with a lower case letter.

7. Each organism is represented by TWOletters, one for each allele.

8. “Purebred” species have two alleles of the same trait • Represented by two of the same letters. This is called homozygous. For instance: BB or bb. • Species with two different alleles or two different forms of the gene would be “hybrid” • Represented by two different “letters” and by called “heterozygous”. For instance: Bb • The alleles present in the organism are referred to as its genotype. For instance, BB, Bb, or bb.

9. The PHYSICAL trait that shows, regardless of genotype is called a PHENOTYPE. • For instance, Blue or Brown Eyes.

10. PROBABILITY • Helps predict the chance that something will happen • Example: the probability of throwing heads or tails on a coin is 50% (1/2 chances) • Your predictions become more accurate with the more trials you run!

11. Using a Punnett Square… • Used to help predict Mendelian genetics

12. Steps for using the Punnett square: • One parent’s alleles (genotype) go along the top • The other parent’s alleles go down the side. • You fill in the squares like doing the communicative property of multiplication. B b B BB Bb b Bb bb

13. Let’s try some practice problems…

14. Practice Problem #1 • Predict the fur color of the offspring of a brown heterozygoushamsters and a white homozygoushamster. Brown is dominant. White is recessive. • Use any letter you like.

15. Practice Problem #1 B b b b

16. Practice Problem #2 • Predict the offspring of 2 white homozygouscows. Black is dominant over white. • Use any letter you like.

17. Practice Problem #2 b b b b

18. Practice Problem #3 • Predict the offspring of 2 Grey Heterozygousrats. Gray is dominant over white, which is recessive. • Use any letter you like.

19. Practice Problem #3 G g G g

20. Practice Problem #4 • Predict the pea shape of the offspring of one HeterozygousRound Pea plant and one homozygouswrinkled pea plant. Round is dominant over wrinkled. • Use any letter you like.

21. Practice Problem #4 R r r r

22. Practice Problem #5you don’t have to write this one down… • What are the chances of having a boy or a girl? • How would you solve this one?

23. Practice Problem #5 X Y X X