Monday, 1/25/10 (Genetics) Check Grades Genetics Lesson Bring Large Milk Cartons (Extra Credit!!) Homework, Due Thursday / Friday Read pgs Answer #'s 1-5 pg 169 Tuesday / Wednesday, 1/26-27 More About Genetics Punnett Squares Packet -Single Factor Crosses Thursday / Friday, 1/28-29 Discuss and Collect Homework Correct Punnett Squares Packet #'s 1-10 Plant Corn for Genetics Lab Start Genetics Problems 1

Genetics

Gregor Mendel  This is Gregor Mendel  He loved math  He loved peas  So he worked at a monastery to find out how certain traits were passed from parents to offspring  He studied traits and inheritance

Peas – The Lucky Plant  Most famous for his work with peas  Peas come in many varieties  Control pollination  Peas have distinctive characteristics

Pea plants have seven observable characteristics. Each characteristic has two possible traits. CharacteristicPossible Trait Plant HeightLong or Short Stems Flower Position on StemAxial or Terminal Pod ColorGreen or Yellow Pod AppearanceInflated or constricted Seed TextureSmooth or Wrinkled Seed ColorYellow or Green Flower ColorPurple or White

Mendel’s Work On Pea Plants   By controlling plant pollination (fertilization), Mendel was able to create pea plants that were true-breeding or “pure” for each trait.   True breeding parent plants always produce offspring with the same trait.

Flower Color Example   A plant true-breeding for purple flowers will always produce offspring with purple flowers.   True breeding plants are called the P 1 generation.

Flower Color Example  He then crossed a true breeding purple plants with a true breeding white plants  This is the P 1 generation

P 1 Generation = true breeding parent

Flower Color Example  The offspring of the P 1 generation is the F 1 generation  1 st Filial (son/daughter)  The offspring were hybrids because the parents had different traits  Purple x White  All offspring were Purple!

F 1 = 1 st Offspring Generation

Dominant and Recessive  Purple “beat” White in the F 1 generation  Mendel called the trait that appeared in the F1 generation the dominant trait.  The trait that did not appear in the F1 generation is the recessive trait.

Law of Segregation  States that for each trait there are 2 controlling factors  During gamete formation (meiosis) these 2 factors separate  Each gamete gets 1 and only 1 factor  When egg is fertilized, the egg now has 2 factors per trait

Crossing F1 Generation  Mendel let the plants from the F1 generation self pollinate.  Did this make true breeding plants?  No!  About ¼ of the plants showed the recessive trait.  White

F 2 Generation

The White trait was hidden in the DNA

Law of independent assortment  This law states that factors (allele pairs) for different characteristics (gene) separate independently during the formation of gametes.  Therefore, traits are transmitted to offspring independently of one another.  Example:  White flowering plant (recessive) with green pod (dominant)

Terms  Homozygous = Both alleles are the same  PP or pp  Heterozygous = alleles are different  1 dominant gene, 1 recessive  Pp  Genotype = Which genes are present  PP = purple  Pp = purple  pp = white  Phenotype = Physical appearance, What we see!  Punnett Squares