4 MENDEL AND PEASGregor Mendel: the 1st person to predict how traits are passed onAustrian (Movarian) Monk ( )Interested in mathematics and botany and combined the two to make a statistical study of peas for a period of eight years ( )
5 WHY MENDEL CHOSE PEAS: 1. Showed some definite characteristics Height: tall and shortFlower color: white and various colorsSeed color: yellow and greenSeed shape: round and wrinkle
6 Peas usually self-pollinate: a. Flower is the reproductive structure in seed plants.Each flower contains stamens which produce pollen grains which form sperm nucleiEach flower contains a pistil which contains egg cells at its base.The transfer of pollen from stamens to pistil results in fertilizationThis called pollination
7 b. Self-Pollination1. Mechanism: Pollen is transferred from stamens to pistil on the same flower or on flowers of the same plant2. Purpose: self- pollinating plants generally breed true generation after generation
8 c. Cross-pollination1. Mechanism: Pollen is transferred from one plant to the flowers of a different plant2. Purpose: Since egg and sperm come from different plants you can study how contrasting traits are passed on in heredity
9 DETERMINATION OF A PURE CHARACTERISTIC Mendel planted seeds of self-pollinated plants to see if they would show the same characteristics as their parent plant.If generation after generation, the characteristic appeared, he called this a pure characteristic.
10 EXAMPLES Seeds from tall plants always produced tall plants Yellow seeds always produce plants that develop yellow seeds
12 THE LAW OF DOMINANCEMendel then cross-pollinated a short plant with a tall plantHe found that one characteristic dominated or masked the otherThis trait he called the dominant traitThe hidden trait was called the recessive traitTall x Short all tall plants (dominant trait)The law of dominance states that in two contrasting characteristics (tall vs. short; wrinkled seeds vs. round seeds) that one characteristic will dominate the other
14 THE F NUMBERThe first generation produced by a cross is called the F1 or first filial (sons & daughters) generationThe second generation after a cross is the F2 (F1 x F1) etc.The parents are designated as P generation
15 THE LAW OF UNIT CHARACTERS 1st generation: Mendel made a Cross of a tall and short pea plant; offspring were all tall2nd generation: crossed 2 plants from the previous generation; offspring were 75% tall and 25% short
16 Law of unit characters Cont. From this observation and w/o knowing about chromosomes and genes or DNA, Mendel developed the Law of Unit Characters:States: that inherited characteristics are controlled by factors (called genes) that occur in pairs
17 How to determine if you are dominant or recessive for a trait Probability: likelihood that a particular trait will exist.Punnett squares: square that shows all possible combinations of alleles that may result.Male alleles go on top of square, female alleles on left side of square.
18 Homozygous or Heterozygous How do you determine if you use 2 capital letters,2 lowercase letters or 1 capital and 1 lowercase letter?Homozygous: 2 identical alleles for a trait.Ex. Mom is homozygous dominant tall-TTDad is homozygous recessive short-tt.Heterozygous: 2 different alleles for a trait.Ex. Mom is heterozygous tall-TtEach parent will be either homozygous or heterozygous for each trait.
19 Phenotype: visible trait (what you see) Genotype: genetic make-up (letters)(height)Ex: Mom is TT.What is her phenotype?What is her genotype?Ex. Dad is Tt.What is his phenotype?What is his genotype?Ex. Daughter is tt.
24 Incomplete dominance: neither allele is dominant or recessive (blended) neither allele is dominant or recessive (blended)
25 Multiple Alleles:. when there are more than 2 alleles for a gene Multiple Alleles: * when there are more than 2 alleles for a gene * in human blood types there 3 possible alleles for the ABO blood typing systemIA = A antigenIB = B antigeni = no antigen" both IA and IB are dominant over i but, " both IA and IB are codominant with each other (that means, they are both expressed equally)
26 Multiple Alleles:. when there are more than 2 alleles for a gene Multiple Alleles: * when there are more than 2 alleles for a gene * in human blood types there 3 possible alleles for the ABO blood typing systemIA = A antigenIB = B antigeni = no antigen" both IA and IB are dominant over i but, " both IA and IB are codominant with each other (that means, they are both expressed equally)Blood Typing