Honors Biology Unit 5 / Chapter 11 Powerpoint #1

Gregor Mendel was born in 1822 in the Czech Republic Studied Science and Mathematics at the University of Vienna Spent the next 14 years teaching high school and working at a monastery in the garden

Mendel noticed that the SAME type of plant could have VARIATIONS, or differences, these are the variations he noticed: Seed ShapeSeed ColorSeed Coat Color RoundYellowGray WrinkledGreenWhite Pod ShapePod ColorFlower PositionPlant Height SmoothGreenAxialTall ConstrictedYellowTerminalShort

 Mendel wanted to breed the pea plants together in different combinations to see what the offspring (seedlings) would look like.

Describe how Mendel prevented self- pollination and controlled cross-pollination in pea plants: He cut off the male parts of one flower, then dusted the stigma with pollen from a second flower. Why did he want to do this? He wanted plants with specific traits to breed with one another.

Genetics: study of heredity (how traits pass from one generation to the next) True-breeding: if allowed to self-pollinate, produce offspring identical to self Self-pollination: pollen from one flower fertilizes egg cells in same flower Cross-pollination: pollen from one flower fertilizes egg cells in a different flower

Trait: specific characteristic that varies from one individual to another Example: Hair color, Eye color, height P generation: parental generation

F 1 generation: first generation of offspring (first filial generation) (AKA kids of parents) F 2 generation: second generation of offspring (offspring of F 1 plants) (AKA grandkids of parents)

Hybrid: offspring of crosses between parents with different traits. Example: Cross pollinate a red flower and a white flower. Seedlings=hybrid X =

Gas + Electric

Gene: segment of DNA that determines a trait Alleles: different forms of a gene (ex: Height: tall gene, or short gene)

Allele

 dominant trait always seen when dominant allele is present; recessive trait only seen when no dominant allele is present

Recessive allele: allele that is masked (hidden) when dominant allele is present  Allele for blue eyes Dominant allele: allele that is always expressed when it is present  Allele for brown eyes

A capital letter represents the dominant allele. A lower case letter represents the recessive allele. Example: Pea plant height – Tall: T Short: t

Segregation of alleles: separation of alleles during gamete production (meiosis) Gametes: sex cells (egg, sperm) Note: all body cells contain two copies of each chromosome (and therefore two copies of each gene) – one copy is from the male parent and one copy is from the female parent During meiosis, each gamete (egg or sperm cell) receives only one copy of each chromosome (and gene (allele)), thus the two copies of each gene are separated.

Seed Shape Flower Position Seed Coat Color Seed Color Pod Color Plant Height Pod Shape Round Wrinkled Round Yellow Green Gray White Smooth Constricted Green Yellow Axial Terminal Tall Short YellowGraySmoothGreen AxialTall

1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics? 2. How do the characteristics of the second generation compare to the characteristics of the first generation? Parents Long stems  short stems Purple flowers  white flowers Green pods  yellow pods Round seeds  wrinkled seeds Yellow seeds  green seeds First Generation All long All purple All green All round All yellow Second Generation 787 long: 277 short 705 purple: 224 white 428 green: 152 yellow 5474 round: 1850 wrinkled 6022 yellow: 2001 green

P Generation F 1 Generation F 2 Generation TallShortTall Short Mendel’s Experiment TTTt tt TTTt tt

Why are there no white flowers in the F 1 generation? The purple parent has 2 purple alleles and the white parent has 2 white alleles. The F 1 plants each have one purple and one white allele – the purple allele is dominant so it masks the white allele. Why are there no light purple flowers in the F 1 generation? Traits do not blend. Explain why the offspring of a true-breeding pea plant with white flowers and a true-breeding pea plant with purple flowers are all purple

How did Mendel show that the recessive allele had not disappeared in the F 1 generation? When he cross-pollinated plants from the F 1 generation, the recessive trait showed up again in the F 2 generation.  This showed Mendel that there must be two factors (genes) controlling each trait – one is dominant and masks the other (which is recessive).

Pea Plant DNA (Electron Microscope)