SMATH #14

-Cans project widely known as Tokyo underground flood tunnels is the networks of tunnels 6.4 kilometers (four miles) long built deep under the ground in the Tokyo suburbs. All this infrastructure is dedicated to prevent flooding when Tokyo metropolitan area rivers are overfilling during the rain seasons or in case of typhoons.

Introduction to Genetics

NotesCH 11

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Introductory Vocabulary

1. Character: inheritable feature of an organisma.Example of characters in pea plants:

Plant height, flower color, seed color, seed shape

2. Trait: variation in an inheritable feature

Slide # 2

Character Traits

Height Tall or Short

Flower Color

Purple or White

Seed Color Yellow or Green

Seed Shape Round or Wrinkled

Introductory Vocabulary

3. Heredity: transfer of traits from parent to offspringa. Inherited traits: traits

received from parentsb. Acquired traits: traits

done to an organism that alter the appearance of the organism

4. Genetics: study of heredity5. Pure breeding: producing

same traits each generation6. Hybrid: offspring from

mating 2 different purebreds

Slide # 3

Character: Stem height

Traits: Tall or dwarf

Gregor Mendel: The Father of Genetics

1. Gregor Mendel: 1822-1884 Austrian monka.Did genetics (breeding)

experiments on garden pea plants.

b.1866: Published paper on experiments

Slide # 4

Gregor Mendel

Gregor J. Mendel, O.S.A., experimental garden (35x7 meters) in the grounds of the Augustinian Monastery in Old Brno. Its appearance before 1922. Courtesy of Villanova University Archives.

The Monastery Garden with the greenhouse which Gregor J. Mendel, O.S.A., had built in 1870. Its appearance before 1902. Courtesy of Villanova University Archives.

The Monastery Garden: Eight Years of Pea Experiments

Why Mendel Chose Pea Plants

1. Mendel chose pea plants for several reasons

a. Grow quickly; grow many generations in short time

b. Produce many offspring

c. Have distinct traits• Tall or dwarf• Yellow or green seeds

d. Could strictly control pollination

Slide # 5

Brushed pollen from a 2nd flower onto carpel (holds eggs) of 1st flower

Cut stamens (holds pollen)off of one flower

Carpel develops into

a pea pod.

Experiments with Pea PlantsThe distinct “either or“ traits.

Seed shape

(Smooth or wrinkled)

Mendel’s Experiment

1. Began with pure breeding parents.2. All traits were the same in BOTH plants EXCEPT the trait being crossed.

3. All F1 generation flowers (first generation) had purple flowers – it appeared as though white trait was lost!

Slide # 6

Purple Flowers X White Flowers

4. Allowed 2 F1’s to self pollinate. In F2 generation, Mendel counted 705 purple flowered plants and 224 white flowered plants. (3 purple:1 white ratio)5. The white flower trait was not lost; it was masked by the purple flower trait!

Question: What were the offspring of this P cross between a white and a purple flowering pea plant?

• The F1 generation plants all had purple flowers.

Question: What happens when the F1 generation of pea plants are allowed to self-fertilize?

• The white trait reappeared!

Question: What was the ratio for purple to white flowering plants in the F2 generation?

• 3 purple :1 white

Seed Shape

Flower Position

Seed CoatColor

Seed Color

Pod Color

Plant Height

PodShape

Round

Wrinkled

Round

Yellow

Green

Gray

White

Smooth

Constricted

Green

Yellow

Axial

Terminal

Tall

Short

Yellow Gray Smooth Green Axial Tall

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Only one trait showed up in F1’s;

& both traits appeared in F2’s at a 3:1 ratio.

Mendel Found a Similar Pattern in Other TraitsSlide # 7

F1

P

Conclusions made by Mendel:1. Each parent MUST contribute one gene for

each trait to the offspring.– Evidence: F2’s had white flowers (present but

hidden in F1 generation.)

2. Each parent must have two copies of a gene; and can have two different versions of that gene called alleles at the same time. -- Evidence: F2’s had white flowers both parents must have had at least one white allele!

Dominant: allele that is expressed when 1 or both are present (capital letter)

Recessive: allele that is masked by presence of dominant allele (lower case)

a. The individual MUST have both recessive alleles to show the recessive trait

Slide # 9

The F1 purple flowering plants

must have a second hidden gene for white flowers!

Alleles1. Alleles: alternate forms of

a gene or trait

a. Parents may have two of the same alleles or two different alleles

b. Homozygous: having 2 identical alleles

c. Heterozygous: having 2 different alleles

2. Alleles are located on chromosomes

This plant has 2 different alleles for the flower color character.

Slide # 8

Every organism has two copies of the same gene. One copy came from MOM in her egg, the other gene copy came from DAD in his sperm.

MOM

DAD

FROM

FROM

Homologous Chromosomes

Homologous Chromosomes:

-are similar gene carrying chromosomes from the opposite-sex parents .

Match these in your head, be ready to share.

Gene

Chromosome

Homologous Pair

Allele

a. Threadlike structures made of DNA found in nucleus

b. Unit of inheritance

c. One form of a gene

d.Two chromosomes that carry the same genes, but just different versions of those genes.

Vocabulary Review

Mendel Solves the Genetics Puzzle

1. Mendel reasoned that each parent must have 2 possible alleles to contribute– Genotype: the alleles the

organism has (two letters)– Phenotype: physical

appearance of an organism

2. Mendel reasoned that the two alleles separated when gametes (sex cells like eggs) formed.

3. Mendel also reasoned that the alleles paired up again during fertilization (joining of egg &sperm)

Genotypes: PP x pp

Gametes: P ~ p

Fertilization: Pp

Genotype of F1: All Pp

Slide # 10

Phenotype of F1: All Purple

Phenotypes: Purple & White

Purebred

Hybrid

To show possible outcomes of genes the new generation will have

We use:

Gene diagrams or

Punnett Squares

Gene Diagram – Flower color

Alleles- P = Purple flower

p = White flower

All genes occur in pairs – so 2 alleles affect a characteristic – possible combinations are;

genotypes PP Pp ppPhenotypesPURPLE PURPLE WHITE

Gene Diagram – Flower color

Male female

Pp Pp

parent

gamete P p P p

Offspring genotype PP PpPppp

Phenotype Purple White Purple Purple 3 purple : 1 white

Punnett SquareAnother method of showing crosses

1. Determine what the alleles are. P=purple p=white

2. Parent genotypes are determined. --Both are Pp

3. Parent’s possible gametes are determined and placed one next to -or above each box.

Pp Purple male

Pp purple female

P p

P

p

Complete the Cross

PP Pp

Pp pp

3 purple and 1 white offspring

3:1 chance with these parents

Punnett Square

Why the White Flowers Reappeared in the F2’s

Slide # 11

Genotype of F1: Pp x Pp

Gametes: ½ P ½ P

½ p ½ p

F2 Genotypes: 1 PP: 2 Pp: 1 pp

F2 Phenotypes: 3 Purple : 1 White

In Summary, Mendel’s Work Showed:

1.Each parent contributes one allele for eachtrait.

2.The two alleles of each trait separate from each other when gametes form (in meiosis) and pair up again during fertilization.

3.Male’s (sperm) and female’s (egg) contribute equally.

4.Acquired traits are not inherited.