1. Notes Chapter 14 Mendel and the Gene Idea
AP Biology 2
Notes Chapter 14
Mendel and the Gene Idea

2. Gregor Mendel Who was Mendel? Pure breeds 3 Generations 4 Hypotheses
Mendel – Austrian Monk in 1850s
Studied pea plant genetics working with flower color
Pure Breeds always produce same trait when self pollinated ex:purple flowers
3 generations P(true breed parents) F1 and F2
4 hypothesis Mendel formed concerning genetics and passing of traits

3. Mendel’s 4 Hypothesis
Alleles account for variation in inherited characteristics
If the 2 alleles differ, dominant is expressed, recessive is hidden
Ex: purple/white flower or round eyes/almond eyes
2 alleles segregate during meiosis
For each character, you inherit 2 alleles
Law of Segregation
One from each parent
Always 50/50 chance for a trait with different alleles

4. Law of Segregation

5. Useful Vocabulary
Homozygous / Heterozygous
Genotype / Phenotype

6. Punnett Squares Monohybrid crosses Dihybrid crosses Test Cross
Pedigrees
Test Cross used to determine genotype of organism w/ dominant phenotype
cross with recessive organism and observe results
Dihybrid Crosses BbEe x bbee
Prove law of independent assortment: each allele is passed seperately in gametes (brown hair is not always associated with brown eyes)
Pedigrees - family tree that can trace a particular trait or disease

7. Rules of Probability Genes are like coins Rules of Multiplication Bio
2 choices & not related to any other gene/coin
Chance is always ½
Rules of Multiplication
p both coins being heads?
Bio
chances of getting white flower from Pp self fertilization?

8. Rules of Probability

9. Exceptions to the 2 Allele Rule
Incomplete Dominance
Codominance
Pleiotropy
Epistasis
Polygenic Inhertiance
Incomplete - hybrids will have appearance inbetween
Codominance -both alleles are expressed (blood types)
dominant traits are not always the more populated. Ie. polydactyly – more than 5 fingers or toes 1/400 born with extra
Pleiotrophy - gene has multiple effects on organism (sickle cell)
Epistasis - 1 gene alters phenotypic expression of another gene
mice coat color 1 trait = black/brown
2nd traint is color/no color (pigment deposted in hair)
Polygenetic Inheritance traits controlled by more than 1 gene. Involve shades of variation (hair color, skin color, height)
Norms 0f Reaction – range of phenotypes possible for a specific genotype, based on environmental factors skin color  suntain, weight  diet

10. Genetic Disorders Dominant genetic disorders
Many not lethal as would not be able to passed on
Huntington’s – late in life deteriorates nervous system (should you find out?)
Recessive genetic disorders
Cystic Fibrosis – must have aa to have it (no code for protein) (27 years)
Tay Sachs – failure to break down brain lipid (3-5 years)
Sickle Cell – Aa have fairly normal function
Multifactorial Diseases
Determined by more than 1 gene and environment
Heart disease, cancer, diabetes, alcoholism

11. Genetic Tools and Counseling
Genetic counseling
Fetal testing
Amniocentesis (Mid pregnancy)(14-16wks)
Chorionic Villi Sampling (Earliest)(8-10wks)
Ultrasound (Anytime)
Fetoscopy
Newborn screening (PKU)