SMATH #14 -Cans project widely known as Tokyo underground flood tunnels is the networks of tunnels...
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Transcript of SMATH #14 -Cans project widely known as Tokyo underground flood tunnels is the networks of tunnels...
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
Go to Section:
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
Go to Section:
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.