Chapter 6:Chapter 6:Introduction to Introduction to

GeneticsGeneticsSection 6-1:Section 6-1:

The Science of Inheritance The Science of Inheritance and and

Gregor MendelGregor Mendel

Parents and OffspringParents and Offspring

HeredityHeredity = biological inheritance= biological inheritance An organism’s heredity is An organism’s heredity is the set of the set of

characteristics it receives from characteristics it receives from its parentsits parents..

GeneticsGenetics is the study of heredity.is the study of heredity. Heredity Heredity IS NOTIS NOT just a blend of just a blend of

characteristics from both parents – characteristics from both parents – look at page 124look at page 124

Gregor MendelGregor Mendel

Born in 1822, became a monk, but also Born in 1822, became a monk, but also studied science and math in Viennastudied science and math in Vienna

In the monastery, Mendel’s job was to In the monastery, Mendel’s job was to take care of the garden (monasteries take care of the garden (monasteries are self-sustaining)are self-sustaining)

He took an interest in pea plants – he He took an interest in pea plants – he began with began with true-breeding stocktrue-breeding stock

True-Breeding StockTrue-Breeding Stock

True-breeding stockTrue-breeding stock refers to refers to individuals that always pass on their individuals that always pass on their characteristics to the next characteristics to the next generation (ex. a tall pea plant with generation (ex. a tall pea plant with green pods will ALWAYS produce green pods will ALWAYS produce tall pea plants with green pods)tall pea plants with green pods)

Reproduction in Pea Reproduction in Pea PlantsPlants

Peas use their flowers to reproduce Peas use their flowers to reproduce (p.125)(p.125)

Male sex cell = pollenMale sex cell = pollen Female sex cell = eggFemale sex cell = egg Pea plants normally Pea plants normally self-pollinateself-pollinate, ,

meaning the pollen and egg come from meaning the pollen and egg come from the same plant (basically only one parent)the same plant (basically only one parent)

True-breeding stock results from True-breeding stock results from generations of self-pollinationgenerations of self-pollination

Mendel and Pea PlantsMendel and Pea Plants

Mendel wanted to see what would Mendel wanted to see what would happen if he crossed true-breeding happen if he crossed true-breeding stock with different characteristicsstock with different characteristics

Mendel removed all the male plant Mendel removed all the male plant parts so that he could control parts so that he could control pollination, making sure that pollen pollination, making sure that pollen and egg came from different plantsand egg came from different plants

This is called This is called cross-pollinationcross-pollination

Mendel’s Seven TraitsMendel’s Seven Traits

Trait = characteristic that identifies Trait = characteristic that identifies one individual from anotherone individual from another

Mendel focused on seven traits, each Mendel focused on seven traits, each with two contrasting forms with two contrasting forms

Mendel’s Seven TraitsMendel’s Seven Traits

TraitTrait Form 1Form 1 Form 2Form 2

Seed shapeSeed shape RoundRound WrinkledWrinkled

Seed colorSeed color YellowYellow GreenGreen

Seed coat Seed coat colorcolor

GrayGray WhiteWhite

Pod shapePod shape SmoothSmooth ConstrictedConstricted

Pod colorPod color GreenGreen YellowYellow

Flower Flower positionposition

AxialAxial TerminalTerminal

Plant heightPlant height TallTall ShortShort

Mendel’s Seven TraitsMendel’s Seven Traits

Mendel used true-breeding stock to Mendel used true-breeding stock to create create hybrids hybrids – offspring of parents – offspring of parents with different characteristicswith different characteristics

The hybrids were called the first The hybrids were called the first filial generation (filial generation (F1 generationF1 generation) ) and the true-breeding stock were and the true-breeding stock were called the parental generation (called the parental generation (P P generationgeneration))

Mendel’s Seven TraitsMendel’s Seven Traits

Mendel noticed the traits seen in the Mendel noticed the traits seen in the F1 generation were not a blending of F1 generation were not a blending of the P generation’s traitsthe P generation’s traits

The traits of only ONE parent The traits of only ONE parent appeared in the offspring while the appeared in the offspring while the traits of the other parent seemed to traits of the other parent seemed to disappeardisappear