Section 10.1 Summary – pages 253-262

2. Section 10.1 Summary – pages 253-262 • Genetics—Branch of biology that studies heredity • Heredity – the passing on of characteristics from parents to offspring • Gregor Mendel--Austrian monk who used pea plants to study how traits are passed from one generation to the next

3. Section 10.1 Summary – pages 253-262 • Traits—characteristics that are inherited • Hybrid—offspring of parents (pea plants) that have different forms of a trait • Ex.—tall pea plant bred with short pea plant

4. Mendel’s Experiment • Cross-pollination—using pollen from one plant to pollinate a different plant • Mendel bred tall pea plants withshort plants • The offspring in the 1st generation were all tall • The offspring in the second generation were 75% tall and 25% short • The short trait disappeared in the 1st generation and reappeared in the 2nd generation

5. Section 10.1 Summary – pages 253-262 • P generation—original parents • F1 generation—offspring of the parent plants (filial) • Ex.Your parents are P and you are F1 P1 Short pea plant Tall pea plant F1 All tall pea plants F2 3 tall: 1 short

6. Section 10.1 Summary – pages 253-262 • Alleles—Different forms of the same gene, each one located on different copies of the same chromosome (1 from mother and 1 from father) • Ex. T is allele for tall plant, t is allele for short plant

7. Section 10.1 Summary – pages 253-262 • Dominant—trait that covers over another trait, capital letter • Ex. T (tall) is a dominant allele • Recessive—trait that is covered over by another trait, lower case letter • Ex. t (short) is the recessive allele T-tall t-short

8. Section 10.1 Summary – pages 253-262 The second generation Seed shape Flower color Pod color Seed color Flower position Pod shape Plant height Dominant trait axial (side) purple yellow round green tall inflated Recessive trait terminal (tips) green short white yellow wrinkled constricted

9. Section 10.1 Summary – pages 253-262 • Phenotype—physical appearance • Ex. Phenotype is tall • Genotype—genetic makeup • Ex. Genotype can be TT for a tall plant Tall pea plant

10. Section 10.1 Summary – pages 253-262 • Homozygous—2 same alleles for a trait • Ex. TT-tall tt-short • Heterozygous—2 different alleles for a trait (carrier) • Ex. Tt-tall TT, Tt-tall tt-short

11. Simple Genetic Human Traits • Tongue Rolling (R) • Dimples (D) • Freckles (F) • Eye Color: Brown is dominant to blue (B) • Hitchhiker’s Thumb (h)

13. Section 10.1 Summary – pages 253-262 • Law of segregation—Each gene has 2 alleles for a trait, after meiosis each gamete receives one of these alleles • Law of Independent assortment – genes for different traits are independently inherited of each other

14. Punnett square--A tool used to predict the possible offspring of a cross between 2 parents • Monohybrid cross--crossing a single trait between 2 parents • Genotype of the parents along top and side of square • Cross each trait individually

15. T T • 1. Cross TT x tt Tt t t Tt Tt Tt Genotypic ratio 100% Tt Phenotypic ratio 100% tall

16. T t • 2. Cross Tt x tt Tt t t tt Tt tt Genotypic ratio 50% Tt 50% tt 1 Tt : 1 tt Phenotypic ratio 50% tall 50% short 1 tall : 1 short

17. 3. Cross Tt x TT T t TT T T Tt TT Tt Phenotypic ratio 100% tall Genotypic ratio 50% TT 50% Tt 1 TT : 1 Tt

18. T t • 4. Cross Tt x Tt TT T t Tt Tt tt Phenotypic ratio 75% tall 25% short 3 tall : 1 short Genotypic ratio 25% TT 50% Tt 25%tt 1 TT : 2 Tt : 1 tt

19. Sex Chromosomes • Every time a female has a baby, what percent chance do they have of having a boy? A girl? • If a female has 5 boys in a row, what percent chance do they have to have another boy? A girl? • Which parent determines the sex of a baby? WHY? • Female (eggs): XX • Male (sperm): XY